



@article {2868,
	title = {Comparison of different methods of heart rate entropy analysis during acute anoxia superimposed on a chronic rat model of pulmonary hypertension},
	journal = {Medical Engineering and Physics},
	volume = {35},
	year = {2013},
	note = {Cited By (since 1996):1Export Date: 12 December 2013Source: Scopus},
	month = {2013///},
	pages = {559 - 568},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84877632838\&partnerID=40\&md5=05c9ef6d6fea4a96d6a63f1749251066},
	author = {Gon{\c c}alves, H. and Henriques-Coelho, T. and Rocha, A.P. and Louren{\c c}o, A.P. and Leite-Moreira, A. and Bernardes, J.}
}
@article {2860,
	title = {Comparison of real beat-to-beat signals with commercially available 4 Hz sampling on the evaluation of foetal heart rate variability},
	journal = {Medical and Biological Engineering and Computing},
	volume = {51},
	year = {2013},
	note = {Export Date: 12 December 2013Source: Scopus},
	month = {2013///},
	pages = {665 - 676},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84877784836\&partnerID=40\&md5=cfdde94007fba73e03e51da6af74b995},
	author = {Gon{\c c}alves, H. and Costa, A. and Ayres-de-Campos, D. and Costa-Santos, C. and Rocha, A.P. and Bernardes, J.}
}
@article {2260,
	title = {Analysis of heart rate variability in a rat model of induced pulmonary hypertension},
	journal = {Medical Engineering and PhysicsMed. Eng. Phys.},
	volume = {32},
	year = {2010},
	note = {Cited By (since 1996): 1Export Date: 21 November 2012Source: ScopusCODEN: MEPHEdoi: 10.1016/j.medengphy.2010.04.018PubMed ID: 20547091Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Geoci{\^e}ncias, Ambiente e Ordenamento do Territ{\'o}rio, Faculdade de Ci{\^e}ncias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptChemicals/CAS: monocrotaline, 315-22-0, 8051-27-2; Ketamine, 6740-88-1; Monocrotaline, 315-22-0References: (2005), ACOG, American College of Obstetricians and Gynecologists. ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists, Number 70, December 2005. Obstet Gynecol 106(6):1453-60Akhavein, F., St.-Michel, E.J., Seifert, E., Rohlicek, C.V., Decreased left ventricular function, myocarditis, and coronary arteriolar medial thickening following monocrotaline administration in adult rats (2007) J Appl Physiol, 103 (1), pp. 287-295;Beckers, F., Verheyden, B., Aubert, A.E., Aging and nonlinear heart rate control in a healthy population (2006) Am J Physiol Heart Circ Physiol, 290 (6), pp. H2560-H2570; 
Bernardes, J., Costa-Pereira, A., A more objective fetal heart rate baseline estimation (1996) Br J Obstet Gynaecol, 103, pp. 714-715; 
Bernardes, J., Gon{\c c}alves, H., Ayres-de-Campos, D., Rocha, A.P., Linear and complex heart rate dynamics vary with sex in relation to fetal behavioural states (2008) Early Hum Dev, 84, pp. 433-439; 
Bruijnzeel, A.W., Stam, R., Croiset, G., Wiegant, G.M., Long-term sensitization of cardiovascular stress responses after a single stressful experience (2001) Physiol Behav, 73 (1-2), pp. 81-86; 
Cerutti, C., Gustin, M.P., Paultre, C.Z., Lo, M., Julien, C., Vincent, M., Autonomic nervous-systempulmonary-edema and cardiovascular variability in rats-a spectral-analysis approach (1991) Am J Physiol, 261 (84), pp. H1292-H1299; 
Court, D.J., Parer, J.T., Nathanielsz, P.W., Parer, J.T., (1984) Experimental studies of fetal asphyxia and fetal heart rate interpretation Research in Perinatal Medicine, pp. 113-169. , Perinatology Press, New York; 
Dudewicz, E., Mishra, S., (1988) Modern mathematical statistics, , Jonh Wiley and Sons, Inc; 
Falcao-Pires, I., Gon{\c c}alves, N., Henriques-Coelho, T., Roncon-Albuquerque, R., Moreira-Gon{\c c}alves, D., Leite-Moreira, A.F., Administration of Apelin modulates myocardial. expression of Apelin-APJ and improves right ventricular performance in MCT-induced pulmonary hypertension (2008) Circulation, 118, pp. S285; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: the effect on linear and nonlinear parameters (2006) Physiol Meas, 27 (3), pp. 307-319; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med Biol Eng Comput, 44 (10), pp. 847-855; 
Gon{\c c}alves, H., Bernardes, J., Rocha, A.P., Ayres-de-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Hum Dev, 83, pp. 585-591; 
Gon{\c c}alves, H., Henriques-Coelho, T., Bernardes, J., Rocha, A.P., Nogueira, A., Leite-Moreira, A., Linear and nonlinear heart rate analysis in a rat model of acute anoxia (2008) Physiol Meas, 29, pp. 1133-1143; 
Henriques-Coelho, T., Correia-Pinto, J., Roncon-Albuquerque, R., Baptista, M.J., Lourenco, A.P., Oliveira, S.M., Endogenous production of ghrelin and beneficial effects of its exogenous administration in monocrotaline-induced pulmonary hypertension (2004) Am J Physiol Heart Circ Physiol, 287 (6), pp. H2885-H2890; 
Henriques-Coelho, T., Oliveira, S.M., Moura, R.S., Roncon-Albuquerque, R., Neves, A.L., Santos, M., Thymulin inhibits monocrotaline-induced pulmonary hypertension modulating interleukin-6 expression and suppressing p38 pathway (2008) Endocrinology, 149 (9), pp. 4367-4373; 
Hessel, M.H.M., Steendijk, P., den Adel, B., Schutte, C.I., van der Laarse, A., Characterization of right ventricular function after monocrotaline-induced pulmonary hypertension in the intact rat (2006) Am J Physiol Heart Circ Physiol, 291 (5), pp. H2424-H2430; 
Kuwahara, M., Yayou, K., Ishii, K., Hashimoto, S., Tsubone, H., Sugano, S., Power spectral analysis of heart rate variability as a new method for assessing autonomic activity in the rat (1994) J Electrocardiol, 27 (4), pp. 333-337; 
Leineweber, K., Brandt, K., Wludyka, B., Beilfuss, A., Ponicke, K., Heinroth-Hoffmann, I., Ventricular hypertrophy plus neurohumoral activation is necessary to alter the cardiac beta-adrenoceptor system in experimental heart failure (2002) Circ Res, 91 (11), pp. 1056-1062; 
Louren{\c c}o, A.P., Roncon-Albuquerque, R., Bras-Silva, C., Faria, B., Wieland, J., Henriques-Coelho, T., Myocardial dysfunction and neurohumoral activation without remodeling in left ventricle of monocrotaline-induced pulmonary hypertensive rats (2006) Am J Physiol Heart Circ Physiol, 291 (4), pp. H1587-H1594; 
Magenes, G., Signorini, M.G., Arduini, D., Cerutti, S., Fetal heart rate variability due to vibroacoustic stimulation: linear and nonlinear contribution (2004) Methods Inf Med, 43 (1), pp. 47-51; 
Marshall, B.E., Longnecker, D.E., General anesthetics (1996) Goodman \& Gilman{\textquoteright}s. The pharmacological basis of therapeutics, , McGraw-Hill, New York, J.G. Hardman, A.G. Gilman, L.E. Limbird (Eds.); 
Martinez, W.L., Martinez, A.R., (2002) Computational statistics handbook with MATLAB, , CRC Press; 
Miller, W.C., Rice, D.L., Kreusel, R.G., Bedrossian, C.W.M., Monocrotaline model of noncardiogenic pulmonary-edema in dogs (1978) J Appl Physiol, 45 (6), pp. 962-965; 
Montenegro, N., Bernardes, J., Ayres-de-Campos, D., Matias, A., Areias, J.C., Monitoring of cardiac-extracardiac haemodynamics and automated fetal heart rate preceding intrauterine death (1996) Eur J Obstet Gynecol Reprod Biol, 64 (1), pp. 3-6; 
Moraru, L., Cimponeriu, L., Tong, S., Thakor, N., Bezerianos, A., Characterization of heart rate variability changes following asphyxia in rats (2004) Methods Inf Med, 43 (1), pp. 118-121; 
Oppenheimer, L.W., Lewinsky, R.M., Power spectral analysis of fetal heart rate (1994) Baillieres Clin Obstet Gynaecol, 8 (3), pp. 643-661; 
Parati, G., Mancia, G., Di Rienzo, M., Castiglioni, P., Taylor, J.A., Studinger, P., Point: Counterpoint: Cardiovascular variability is/is not an index of autonomic control of circulation (2006) J Appl Physiol, 101 (2), pp. 676-682; 
Pincus, S., Viscarello, R., Approximate Entropy: A regularity measure for fetal heart rate analysis (1992) Obstet Gynecol, 79, pp. 249-255; 
Pincus, S., Aproximate entropy (ApEn) as a complexity measure (1995) Chaos, 5, pp. 110-117; 
Pincus, S.M., Gevers, E.F., Robinson, I.C.A.F., VanDenBerg, G., Roelfsema, F., Hartman, M.L., Females secrete growth hormone with more process irregularity than males in both humans and rats (1996) Am J Physiol-Endocrinol Metab, 270 (1), pp. E107-E115; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. H2039-H2049; 
Sanyal, S.N., Ono, K., Derangement of autonomic nerve control in rat with right ventricular failure (2002) Pathophysiology, 8 (3), pp. 197-203; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans Biomed Eng, 50, pp. 365-373; 
(1996), Task force, Heart rate variability - standards of measurement, physiological interpretation and clinical use Circulation 93 1043-65 Task force of the European Society of Cardiology and the North American Society of Pacing and ElectrophysiologyTaylor, J.A., Studinger, P., Cardiovascular variability is/is not an index of autonomic control of circulation (2006) J Appl Physiol, 101 (2), pp. 690-691; 
Welch, P.D., The use of Fast Fourier Transform for the estimation of power spectra: a method based on time averaging over short, modified periodograms (1967) IEEE Trans Audio Electroacous, AU-15 (2), pp. 70-73; 
Yum, M.K., Park, E.Y., Kim, C.R., Hwang, J.H., Alterations in irregular and fractal heart rate behavior in growth restricted fetuses (2001) Eur J Obstet Gynecol, 94, pp. 51-58
},
	month = {2010///},
	pages = {746 - 752},
	abstract = {Monocrotaline (MCT) is commonly used to experimentally induce pulmonary hypertension (PH), which might lead to chronic heart failure. In this study, linear and non-linear heart rate (HR) dynamics were weekly assessed in MCT-treated and non-treated Wistar rats.The HR of 10 adult Wistar rats injected with MCT (MCT group) and of 10 similar rats injected with vehicle (non-MCT group), anesthetized with Ketamine, was weekly recorded during 4 weeks. The first four segments of 1-min length of each HR recording were analysed using linear, time and frequency domains, and approximate (ApEn) and sample (SampEn) entropy indices, considering recently proposed values for the threshold parameter of ApEn and SampEn. Statistical analysis was performed using 95\% confidence intervals and statistical tests.Along the study period, an overall weekly maintenance of HR indices, or a decrease, namely in weeks 1-2, was manifest, in the MCT group, except for LF and LF/HF, in week 1, denoting a short-term increase in sympathetic activity without any other changes. On the other hand, a maintenance of HR indices, or an increase, namely on week 4, was observed in the non-MCT group, except for LF/HF, denoting a long-term increase of the overall activity of HR control systems, with a parasympathetic like dominance.Studies on long-term HR dynamics should be performed in very carefully controlled experimental settings, as significant weekly changes may occur, both among anesthetized MCT-treated and non-treated rats. {\textcopyright} 2010 IPEM.},
	keywords = {adrenergic activity, Amines, animal experiment, animal model, Animals, article, cholinergic activity, Chronic heart failures, Confidence interval, controlled study, Disease Models, Animal, Electrocardiography, entropy, Female, Frequency domain analysis, Frequency domains, Heart, heart electrophysiology, Heart rate, Heart rate variability, Heart rate variability (HRV), Heart rates, Hypertension, Pulmonary, Injections, Subcutaneous, Ketamine, Maintenance, Monocrotaline, Non-linear, nonhuman, priority journal, Pulmonary hypertension, rat, Rat model, Rats, Rats, Wistar, Statistical analysis, statistical parameters, Sympathetic activities, Threshold parameters, Time and frequency domain analysis, Time domain analysis, Time Factors, Wistar rat, Wistar rats},
	isbn = {13504533 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-77955279673\&partnerID=40\&md5=5fa2879d821f37e48f50a723fa1cb225},
	author = {Gon{\c c}alves, H. and Henriques-Coelho, T. and Bernardes, J. and Rocha, A.P. and Brand{\~a}o-Nogueira, A. and Leite-Moreira, A.}
}
@article {2314,
	title = {Sex differences in linear and complex fetal heart rate dynamics of normal and acidemic fetuses in the minutes preceding delivery},
	journal = {Journal of Perinatal MedicineJ. Perinat. Med.},
	volume = {37},
	year = {2009},
	note = {Cited By (since 1996): 4Export Date: 21 November 2012Source: ScopusCODEN: JPEMAdoi: 10.1515/JPM.2009.024PubMed ID: 19021459Language of Original Document: EnglishCorrespondence Address: Bernardes, J.; Faculdade de Medicina, Universidade Do Porto, Ginecologia e Obstetr{\'\i}cia, Al. Hernani Monteiro, Porto, 4200, Portugal; email: jbernardes59@gmail.comReferences: Ayres-de-Campos, D., Bernardes, J., Costa-Pereira, A., Pereira-Leite, L., Inconsistencies in classification by experts of cardiotocograms and subsequent clinical decision (1999) Br J Obstet Gynaecol, 106, pp. 1307-1310;Ayres-de-Campos, D., Bernardes, J., Garrido, A., Marques-de-S{\`a}, J.P., Pereira-Leite, L., SisPorto 2.0 - a program for automated analysis of cardiotocograms (2000) J Matern Fetal Med, 9, pp. 311-318; 
Ayres-de-Campos, D., Costa-Santos, C., Bernardes, J., SisPorto Multicentre Validation Study Group. Prediction of neonatal state by computer analysis of fetal heart rate tracings: The antepartum arm of the SisPorto multicentre validation study (2005) Eur J Obstet Gynecol Reprod Biol, 118, pp. 52-60; 
Ayres-de-Campos, D., Sousa, P., Costa, A., Bernardes, J., Omniview-SisPorto 3.5 - a central fetal monitoring station with online alerts based on computerized cardio-tocogram+ST event analysis (2008) J Perinat Med, 36, pp. 260-264; 
Beckers, F., Verheyden, B., Aubert, A.E., Aging and non-linear heart rate control in a healthy population (2006) Am J Physiol Heart Circ Physiol, 290, pp. H2560-H2570; 
Bekedam, D.J., Engelsbel, S., Mol, B.W., Buitendijk, S.E., van der Pal-de Bruin, K.M., Male predominance in fetal distress during labor (2002) Am J Obstet Gynecol, 187, pp. 1605-1607; 
Bennet, L., Booth, L.C., Ahmed-Nasef, N., Dean, J.M., Davidson, J., Quaedackers, J.S., Male disadvantage? Fetal sex and cardiovascular responses to asphyxia in preterm fetal sheep (2007) Am J Physiol Regul Integr Comp Physiol, 293, pp. R1280-R1286; 
Bernardes, J., Moura, C., Marques-de-S{\'a}, J.P., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J Perinat Med, 19, pp. 61-65; 
Bernardes, J., Costa-Pereira, A., Ayres-de-Campos, D., van Geijn, H.P., Pereira-Leite, L., Evaluation of interobserver agreement of cardiotocograms (1997) Int J Gynecol Obstet, 57, pp. 33-37; 
Bernardes, J., Ayres-de-Campos, D., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int J Gynaecol Obstet, 62, pp. 141-147; 
Bernardes, J., Gon{\c c}alves, H., Ayres-de-Campos, D., Rocha, A.P., Linear and complex heart rate dynamics vary with sex in relation to fetal behavioural states (2008) Early Hum Dev, 84, pp. 433-439; 
Boog, G., Analyse informatis{\'e}e du rythme cardiaque foetal au cours de la grosssesse et de l{\textquoteright}accouchement. (2004) Encyclop{\'e}die M{\'e}dico- Chirurgicale, 148, pp. 1-10; 
Browner, W.S., Newman, T.B., Cummings, S.R., Hulley, S.B., (2001) Estimating sample size and power: The nitty-gritty, pp. 65-84. , Hulley SB, Cummings SR, Browner WS, Grady D, Hearst N, Newman TB, editors. Philadelphia: Lippincot Williams \& Wilkins; 
Chaffin, D.G., Barnard, J.M., Phernetton, T., Reed, K.L., Decreased approximate entropy of heart rate variability in the hypoxic ovine fetus (1998) J Matern Fetal Invest, 8, pp. 23-26; 
Dawes, G.S., Moulden, M., Redman, C.W., Improvements in computerized fetal heart rate analysis antepartum (1996) J Perinat Med, 24, pp. 25-36; 
Dawes, N.W., Dawes, G.S., Moulden, M., Redman, C.W., Fetal heart rate patterns in term labor vary with sex, gestational age, epidural analgesia, and fetal weight (1999) Am J Obstet Gynecol, 180, pp. 181-187; 
DiPietro, J.A., Costigan, K.A., Shupe, A.K., Pressman, E.K., Johnson, T.R., Fetal neurobehavioral development: Associations with socioeconomic class and fetal sex (1998) Dev Psychobiol, 33, pp. 79-91; 
Dudewicz, E., Mishra, S., (1998) Modern mathematical statistics, , John Wiley and Sons, Inc; 
Fleisher, L.A., Dipietro, J.A., Johnson, T.R., Pincus, S., Complementary and non-coincident increases in heart rate variability and irregularity during fetal development (1997) Clin Sci (Lond), 92, pp. 345-349; 
Fusheng, Y., Bo, H., Qingyu, T., (1998) Approximate entropy and its application in biosignal analysis, 2, pp. 72-91. , editor. Nonlinear biomedical signal processing, Dynamical analysis and modelling. IEEE Press;; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters (2006) Physiol Meas, 27, pp. 307-319; 
Goncalves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med Biol Eng Comput, 44, pp. 847-855; 
Goncalves, H., Bernardes, J., Rocha, A.P., Ayres-de-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Hum Dev, 83, pp. 585-591; 
Groome, L.J., Mooney, D.M., Holland, S.B., Smith, L.A., Atterbury, J.L., Dykman, R.A., Behavioral state affects heart rate response to low-intensity sound in human fetuses (1999) Early Hum Dev, 54, pp. 39-54; 
Ingemarsson, I., Herbst, A., Thorngren-Jerneck, K., Long-term outcome after umbilical artery acidemia at term birth: Influence of gender and duration of fetal heart rate abnormalities (1997) Br J Obstet Gynaecol, 104, pp. 1123-1127; 
Jensen-Urstad, K., Storck, N., Bouvier, F., Ericson, M., Lindblad, L.E., Jensen-Urstad, M., Heart rate variability in healthy subjects is related to age and gender (1997) Acta Physiol Scand, 160, pp. 235-241; 
King, T., Parer, J., The physiology of fetal heart rate patterns and perinatal asphyxia (2000) J Perinat Neonat Nurs, 14, pp. 19-39; 
Kuo, T.B., Yang, C.C., Sexual dimorphism in the complexity of cardiac pacemaker activity (2002) Am J Physiol Heart Circ Physiol, 283, pp. H1695-H1702; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) J Obstet Gynecol Reprod Biol, 114, pp. 137-143; 
Magenes, G., Signorini, M.G., Arduini, D., Classification of cardiotocographic records by neural networks (2000) IJCNN 2000, Proceedings of the IEEE-INNS-ENNS International Joint Conference on Neural Networks, 3, pp. 637-641; 
Martinez, W.L., Martinez, A.R., (2002) Computational statistics handbook with MATLAB, , CRC Press;; 
Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc Natl Acad Sci USA, 88, pp. 2297-2301; 
Pincus, S., Viscarello, R., Approximate Entropy: A regularity measure for fetal heart rate analysis (1992) Obstet Gynecol, 79, pp. 249-255; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. H2039-H2049; 
Ryan, S.M., Goldberger, A.L., Pincus, S.M., Mietus, J., Lipsitz, L.A., Gender- and age-related differences in heart rate dynamics: Are women more complex than men? (1994) J Am Coll Cardiol, 24, pp. 1700-1707; 
Sheiner, E., Hadar, A., Hallak, M., Katz, M., Mazor, M., Shoham-Vardi, I., Clinical significance of fetal heart rate tracings during the second stage of labor (2001) Obstet Gynecol, 97, pp. 747-752; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Transactions on Biomedical Engineering, 50, pp. 365-373; 
Siira, S.M., Ojala, T.H., Vahlberg, T.J., Jalonen, J.O., V{\"a}lim{\"a}ki, I.A., Ros{\'e}n, K.G., Marked fetal acidosis and specific changes in power spectrum analysis of fetal heart rate variability recorded during the last hour of labor (2005) Br J Obstet Gynaecol, 112, pp. 418-423; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Yaegashi, N., Murotsuki, J., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am J Obstet Gynecol, 182, pp. 1227-1232; 
},
	month = {2009///},
	pages = {168 - 176},
	abstract = {Aim: To assess linear and complex heart rate dynamics in relation to fetal gender in normal and acidemic fetuses during the minutes preceding delivery. Methods: Linear and non-linear fetal heart rate indices, namely mean FHR, long-term irregularity index, short-term variability, low and high frequency spectral indices, approximate and sample entropy, were assessed in 36 female and 30 male fetuses, adjusted for gestational age and weight, during the minutes preceding delivery. Analysis was performed in the initial and final minutes of each tracing in fetuses with umbilical artery blood pH at delivery >=7.20, 7.11-7.19 and <=7.10. Results: Progression of labor was associated with a significant decrease in non-linear indices and an increase in almost all linear indices, both in female and male fetuses, but changes were more marked in female fetuses. Non-acidemic females showed higher mean FHR in the final minutes of labor, compared with males. Acidemic females had higher linear indices when compared to similar male fetuses. Conclusions: During the minutes preceding delivery, female fetuses express higher linear indices than male fetuses, suggesting greater activation of the autonomic nervous system, while maintaining similar complexity indices, which suggests different reaction and adaptation capabilities to stress and distress. {\textcopyright} 2009 by Walter de Gruyter.},
	keywords = {acidemia, Acidemic fetuses, article, autonomic nervous system, Birth Weight, blood pH, Cross-Sectional Studies, delivery, Delivery, Obstetric, entropy, Entropy and spectral analysis, Female, Fetal Heart, fetus, fetus heart rate, Gestational Age, Heart Rate, Fetal, human, Humans, Hydrogen-Ion Concentration, Intrapartum, labor, Labor, Obstetric, male, Pregnancy, priority journal, Retrospective Studies, Sex Characteristics, sex difference, Umbilical Arteries, umbilical artery},
	isbn = {03005577 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-59449089216\&partnerID=40\&md5=7a093bd5c056231b3f8150912abca652},
	author = {Bernardes, J. and Gon{\c c}alves, H. and Ayres-de-Campos, D. and Rocha, A.P.}
}
@article {2349,
	title = {Frequency domain and entropy analysis of fetal heart rate: Appealing tools for fetal surveillance and pharmacodynamic assessment of drugs},
	journal = {Cardiovascular and Hematological Disorders - Drug TargetsCardiovasc. Hematol. Disord. Drug Targets},
	volume = {8},
	year = {2008},
	note = {Cited By (since 1996): 1Export Date: 21 November 2012Source: Scopusdoi: 10.2174/187152908784533720Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptChemicals/CAS: atropine, 51-55-8, 55-48-1; betamethasone, 378-44-9; lidocaine, 137-58-6, 24847-67-4, 56934-02-2, 73-78-9; magnesium sulfate, 7487-88-9; opiate, 53663-61-9, 8002-76-4, 8008-60-4; propranolol, 13013-17-7, 318-98-9, 3506-09-0, 4199-09-1, 525-66-6; salbutamol, 18559-94-9References: Task-Force. Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (1996) Eur. Heart J, 17, pp. 354-381;Beckers, F., Verheyden, B., Aubert, A.E., Aging and nonlinear heart rate control in a healthy population (2006) Am. J. Physiol. Heart Circ. Physiol, 29, pp. H2560-H2570; 
Pincus, S.M., Minkin, M.J., Assessing sequential irregularity of both endocrine and heart rate rhythms (1998) Curr. Opin. Obstet. Gynecol, 1 (4), pp. 281-291; 
Rooth, G., Huch, A., Huch, R., Guidelines for the use of fetal monitoring (1987) Int. J. Gynecol. Obstet, 25, pp. 159-167; 
American College of Obstetricians and Gynecologists. ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists, Number 70, December 2005 (2005) Int. J. Gynecol. Obstet, 1, pp. 1453-1460. , ACOG; 
(2001) Royal College of Obstetricians and Gynaecologists. Evidence-Based Clinical Guideline Number 8. The Use of Electronic Fetal Monitoring, , RCOG, Royal College of Obstetricians and Gynaecologists: London; 
International Federation of Gynecology and Obstetrics. Intrapartum surveillance: Recommendations on current practice and overview of new developments. FIGO Study Group on the Assessment of New Technology. International Federation of Gynecology and Obstetrics (1995) Int. J. Gynecol. Obstet, 49 (2), pp. 213-221. , FIGO; 
National Institute of Child Health and Human Development Research Planning Worlshop. Electronic fetal heart rate monitoring: Research guidelines for interpretation (1997) Am. J. Obstet. Gynecol, 177, pp. 1385-1390. , NICH; 
Dawes, G.S., Moulden, M., Redman, C.W.G., System 8000 - Computerized antenatal FHR analysis (1991) J. Perinat. Med, 19 (1-2), pp. 47-51; 
Bernardes, J., Moura, C., Marques-de-S{\'a}, J.P., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J. Perinat. Med, 19, pp. 61-65; 
Ayres-de-Campos, D., Bernardes, J., Garrido, A., Marques-de-S{\'a}, J., Pereira-Leite, L., SisPorto 2.0: A program for automated analysis of cardiotocograms (2000) J. Mat. Fet. Med, 9, pp. 311-318; 
Bernardes, J., Ayres-de-Campos, D., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int. J. Gynecol. Obstet, 2, pp. 141-147; 
Bernardes, J., Costa-Pereira, A., The effect of different sampling intervals on the measurement of intrapartum fetal heart rate variability. Letter to the Editor (1997) Obstet. Gynecol, 9, pp. 318-319; 
Ayres-de-Campos, D., Bernardes, J., Costa-Pereira, A., Pereira-Leite, L., Inconsistencies in expert{\textquoteright}s classification of cardiotocograms and subsequent clinical decision (1999) Br. J. Obstet. Gynecol, 1, pp. 1307-1310; 
Ayres-de-Campos, D., Bernardes, J., Early, variable and late decelerations: Can a consensus be reached in their identification? (1999) Int. J. Gynecol. Obstet, 5 (3), pp. 305-306; 
Grant, J.M., The fetal heart rate trace is normal, isn{\textquoteright}t it? Observer agreement of categorical assessments (1991) Lancet, 337, pp. 215-218; 
Bernardes, J.; Costa-Pereira, A. Efficacy and safety of intrapartum electronic fetal monitoring: An update. Obstet. Gynecol., 1996}, 87 3, 476-477Bernardes, J., Costa-Pereira, A., Admission cardiotocography (2003) Lancet, 3 (1), p. 1741; 
Alfirevic, Z., Devane, D., Gyte, G.M.L., Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour (2006) Coch. Data. Sys. Rev, 3; 
Pincus, S., Viscarello, R., Approximate Entropy: A regularity measure for fetal heart rate analysis (1992) Obstet. Gynecol, 79 (2), pp. 249-255; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans. Biomed. Eng, 5 (3), pp. 365-373; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med. Biol. Eng. Comput, 44 (1), pp. 847-855; 
Gon{\c c}alves, H., Bernardes, J., Rocha, A.P., Ayres-de-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Hum. Dev, 83, pp. 585-591; 
Parer, J.T., (1997) Handbook of Fetal Heart Rate Monitoring, , W. B. Saunders Company: Philadelphia, Pennsylvania; 
Oppenheimer, L.W., Lewinsky, R.M., Power spectral analysis of fetal heart rate (1994) Baillieres Clin. Obstet. Gynaecol, 8 (3), pp. 643-661; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Yaegashi, N., Murotsuki, J., Uehara, S., Yajima, A., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am. J. Obstet. Gynecol, 182, pp. 1227-1232; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Wu, G., Shen, L., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) Eur. J. Obstet. Gynecol. Reprod. Biol, 114, pp. 137-143; 
Court, D.J., Parer, J.T., In Research in Perinatal Medicine (1984) Experimental studies of fetal asphyxia and fetal heart rate interpretation, pp. 113-169. , Nathanielsz, P.W, Parer, J.T; Eds, Perinatology Press: New York; 
vanGeijn, H.P., Developments in {CTG} analysis (1996) Baillieres Clin. Obstet. Gynaecol, 1 (2), pp. 185-209; 
Bernardes, J., Costa-Pereira, A., A more objective fetal heart rate baseline estimation (1996) Br. J. Obstet. Gynaecol, 1 (3), pp. 714-715; 
Ayres-de-Campos, D., Bernardes, J., Marsal, K., Nickelsen, C., Makarainen, L., Banfield, P., Xavier, P., Campos, I., Can the reproducibility of fetal heart rate baseline estimation be improved? (2004) Eur. J. Obstet. Gynecol. Reprod. Biol, 112, pp. 49-54; 
Ayres-de-Campos, D., Santos, C., Bernardes, J., Prediction of neonatal state by computer analysis of fetal heart rate tracings: The antepartum arm of the SisPorto {\textregistered} multicentre validation study (2005) Eur. J. Obstet. Gynecol. Reprod. Biol, 118 (1), pp. 52-60; 
Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc. Natl. Acad. Sci. USA, 88, pp. 2297-2301; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am. J. Physiol. Heart. Circ. Physiol, 278, pp. H2039-H2049; 
Fusheng, Y., Bo, H., Qingyu, T., (1998) Nonlinear biomedical signal processing - Volume II: Dynamical analysis and modelling, pp. 72-91. , Ed, Approximate entropy and its application in biosignal analysis; IEEE Press: New York; 
Pincus, S., Approximate entropy (ApEn) as a complexity measure (1995) Chaos, 5 (1), pp. 110-117; 
Hayes, M., (1996) Statistical digital signal processing and modelling, , Jonh Wiley and Sons, Inc.:New York; 
Boog, G., Analyse informatis{\'e}e du rythme cardiaque foetal au cours de la grossesse et de l{\textquoteright}accouchement (2004) Encyclop{\'e}die M{\'e}dico-Chirurgicale, 148, pp. 1-10. , 5.049-D-23; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters (2006) Physiol. Meas, 27, pp. 307-319; 
Magenes, G., Signorini, M.G., Arduini, D., Cerutti, S., Fetal heart rate variability due to vibroacoustic stimulation: Linear and nonlinear contribution (2004) Methods Inf. Med, 43 (1), pp. 47-51; 
Hallak, M.; Martinez-Poyer, J.; Kruger, M.L.; Hassan, S.; Blackwell, S.C.; Sorokin, Y. The effect of magnesium sulfate on fetal heart rate parameters: A randomized, placebo-controlled trial. Am. J. Obstet. Gynecol., 1999, 181 5 Part 1, 1122-1127Swartjes, J.M., van Geijn, H.P., Meinardi, H., Mantel, R., Fetal heart-rate patterns and chronic exposure to antiepileptic drugs (1992) Epilepsia, 33 (4), pp. 721-728; 
Bernardes, J., Costa-Pereira, A., Ayres-de-Campos, D., van Geijn, H.P., Pereira-Leite, L., Evaluation of interobserver agreement of cardiotocograms (1997) Int. J. Gynecol. Obstet, 57 (1), pp. 33-37; 
Rotmensch, S., Lev, S., Kovo, M., Efrat, Z., Zahavi, Z., Lev, N., Celentano, C., Ben-Rafael, Z., Effect of betamethasone administration on fetal heart rate tracing: A blinded longitudinal study (2005) Fetal. Diagn. Ther, 2 (5), pp. 371-376; 
Lunshof, M.S., Boer, K., Wolf, H., Koppen, S., Velderman, J.K., Mulder, E.J.H., Short-term (0-48h) effects of maternal betamethasone administration on fetal heart rate and its variability (2005) Pediatr. Res, 57 (4), pp. 545-549; 
Beckers, F.; Verheyden, B.; Ramaekers, D.; Swinghedauw, B.; Aubert, A.E. Effects of autonomic blockade on non-linear cardiovascular variability indices in rats. Clin. Exp. Pharmacol. Physiol., 2006, 33 5-, 431-439Georgoulas, G., Stylios, C.D., Groumpos, P.P., Predicting the risk of metabolic acidosis for newborns based on fetal heart rate signal classification using support vector machines (2006) IEEE Trans. Biomed. Eng, 53 (5), pp. 875-884; 
DiRenzo, G.C., Montani, M., Fioriti, V., Clerici, G., Branconi, F., Pardini, A., Indraccolo, R., Cosmi, E.V., Fractal analysis: A new method for evaluating fetal heart rate variability (1996) J. Perinat. Med, 24 (3), pp. 261-269; 
Felgueiras, C., Marques-de-S{\'a}, J.P., Bernardes, J., Gama, S., Fractal characterisation of fetal heart rate sequences (1998) Biomed. Eng, 3 (2), pp. 197-201; 
},
	month = {2008///},
	pages = {91 - 98},
	abstract = {Recently, frequency domain and entropy analysis of fetal heart rate (FHR) have been assessed in several studies, providing new insights into physiologic regulatory mechanisms, constituting appealing tools for pharmacodynamic assessment, namely during fetal life. There is evidence that entropy and frequency domain analysis convey information on cortical and autonomic nervous system activities, respectively. Use of internal versus external FHR acquisition sensors and the signal sampling frequency may dramatically affect results. Most FHR frequency domain indices are significantly increased with rising fetal activity, namely during active wakefulness and active sleep, whereas the opposite occurs with nonlinear indices. This is in favour of increased activity of the autonomous nervous system and decreased activity of the central nervous system complexity control systems, during periods of fetal activity. Progression of labor is associated with a significant increase in FHR frequency domain indices, whereas entropy indices are significantly decreased. This denotes activation of the autonomic nervous system in the final minutes of labour, associated with decreased central nervous system activity. The emerging knowledge on FHR frequency domain and entropy analysis substantiates a continued interest of these methods in evaluation of the fetal pathophysiologic regulatory mechanisms, and opens new perspectives for clinical and pharmacodynamic assessment. {\textcopyright} 2008 Bentham Science Publishers Ltd.},
	keywords = {acidemia, adrenergic receptor stimulating agent, alpha adrenergic receptor blocking agent, anticonvulsive agent, article, atropine, autonomic nervous system function, beta adrenergic receptor blocking agent, betamethasone, Cardiotocography, central depressant agent, central nervous system function, cholinergic receptor blocking agent, chronotropism, Computerized analysis, drug effect, drug mechanism, electronic sensor, entropy, External and internal monitoring, Female, Fetal behavioral states, Fetal heart rate (FHR), Fetal monitoring, fetus, fetus heart rate, fetus monitoring, frequency analysis, Frequency domain and entropy analysis, gestation period, Heart rate variability, Heart Rate, Fetal, human, Humans, instrumentation, labor, lidocaine, local anesthetic agent, magnesium sulfate, mathematical computing, methodology, nonhuman, opiate, pharmacodynamics, physiology, Pregnancy, prenatal screening, propranolol, pulse rate, review, salbutamol, signal detection},
	isbn = {1871529X (ISSN)},
	author = {Gon{\c c}alves, H. and Rocha, A.P. and Ayres-de-Campos, D. and Bemardes, J.}
}
@article {2347,
	title = {Linear and complex heart rate dynamics vary with sex in relation to fetal behavioural states},
	journal = {Early Human DevelopmentEarly Hum. Dev.},
	volume = {84},
	year = {2008},
	note = {Cited By (since 1996): 16Export Date: 21 November 2012Source: ScopusCODEN: EHDEDdoi: 10.1016/j.earlhumdev.2007.12.001PubMed ID: 18248921Language of Original Document: EnglishCorrespondence Address: Bernardes, J.; Departamento de Ginecologia e Obstetr{\'\i}cia, Faculdade de Medicina, Universidade do Porto and INEB (Instituto Nacional de Engenharia Biom{\'e}dica), Porto, Portugal; email: jbernardes@mail.telepac.ptReferences: Ingemarsson, I., Herbst, A., Thorngren-Jerneck, K., Long term outcome after umbilical artery acidaemia at term birth: influence of gender and duration of fetal heart rate abnormalities (1997) Br J Obstet Gynaecol, 104 (10), pp. 1123-1127;Ingemarsson, I., Gender aspects of preterm birth (2003) BJOG, 110 (SUPPL. 20), pp. 34-38; 
DiPietro, J.A., Hodgson, D.M., Costigan, K.A., Hilton, S.C., Johnson, T.R., Development of fetal movement-fetal heart rate coupling from 20~weeks through term (1996) Early Hum Dev, 44 (2), pp. 139-151; 
DiPietro, J.A., Costigan, K.A., Shupe, A.K., Pressman, E.K., Johnson, T.R., Fetal neurobehavioral development: associations with socioeconomic class and fetal sex (1998) Dev Psychobiol, 33 (1), pp. 79-91; 
Ogueh, O., Steer, P., Gender does not affect fetal heart rate variation (1998) Br J Obstet Gynaecol, 105 (12), pp. 1312-1314; 
Dawes, N.W., Dawes, G.S., Moulden, M., Redman, C.W., Fetal heart rate patterns in term labor vary with sex, gestational age, epidural analgesia, and fetal weight (1999) Am J Obstet Gynecol, 180, pp. 181-187; 
Lange, S., Van Leeuwen, P., Geue, D., Hatzmann, W., Gronemeyer, D., Influence of gestational age, heart rate, gender and time of day on fetal heart rate variability (2005) Med Biol Eng Comput, 43 (4), pp. 481-486; 
Gon{\c c}alves, H., Bernardes, J., Rocha, A.P., Ayres-de-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Hum Dev, 83 (9), pp. 585-591; 
Nijhuis, J.G., Prechtl, H.F., Martin Jr., C.B., Bots, R.S., Are there behavioural states in the human fetus? (1982) Early Hum Dev, 6 (2), pp. 177-195; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-de-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: the effect on linear and nonlinear parameters (2006) Physiol Meas, 27 (3), pp. 307-319; 
Goncalves, H., Rocha, A.P., Bernardes, J., Ayres-de-Campos, D., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med Biol Eng Comput, 44 (10), pp. 847-855; 
Ayres-de-Campos, D., Bernardes, J., Garrido, A., Marques-de-S{\'a}, Pereira-Leite, L., SisPorto 2.0 - a program for automated analysis of cardiotocograms (2000) J Matern Fetal Med, 9, pp. 311-318.; 
Magenes, G., Signorini, M.G., Arduini, D., Classification of cardiotocographic records by neural networks (2000) IJCNN 2000, Proceedings of the IEEE-INNS-ENNS International Joint Conference on Neural Networks, 3, pp. 637-641; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans Biomed Eng, 50, pp. 365-373; 
Task force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, Heart rate variability - standards of measurement, physiological interpretation and clinical use (1996) Circulation, 17, pp. 354-381; 
Boog, G., Analyse informatis{\'e}e du rythme cardiaque foetal au cours de la grosssesse et de l{\textquoteright}accouchement (2004) Encyclop{\'e}die M{\'e}dico-Chirurgicale, 148 (5-49 -D-23), pp. 1-10; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Yaegashi, N., Murotsuki, J., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am J Obstet Gynecol, 182, pp. 1227-1232; 
Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc Natl Acad Sci U. S. A., 88, pp. 2297-2301; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. H2039-H2049; 
Fusheng, Y., Bo, H., Qingyu, T., Approximate entropy and its application in biosignal analysis (1998) Nonlinear biomedical signal processing - Volume II: Dynamical analysis and modelling, pp. 72-91. , Akay M. (Ed), IEEE Press; 
Pincus, S., Viscarello, R., Approximate entropy: a regularity measure for fetal heart rate analysis (1992) Obstet Gynecol, 79, pp. 249-255; 
Martinez, W.L., Martinez, A.R., (2002) Computational statistics handbook with MATLAB, , CRC Press; 
Dudewicz, E., Mishra, S., (1998) Modern Mathematical Statistics, , John Wiley and Sons, Inc; 
Robles de Medina, P.G., Visser, G.H., Huizink, A.C., Buitelaar, J.K., Mulder, E.J., Fetal behaviour does not differ between boys and girls (2003) Early Hum Dev, 73 (1-2), pp. 17-26; 
Ryan, S.M., Goldberger, A.L., Pincus, S.M., Mietus, J., Lipsitz, L.A., Gender- and age-related differences in heart rate dynamics: are women more complex than men? (1994) J Am Coll Cardiol, 24 (7), pp. 1700-1707; 
Jensen-Urstad, K., Storck, N., Bouvier, F., Ericson, M., Lindblad, L.E., Jensen-Urstad, M., Heart rate variability in healthy subjects is related to age and gender (1997) Acta Physiol Scand, 160 (3), pp. 235-241; 
Beckers, F., Verheyden, B., Aubert, A.E., Aging and nonlinear heart rate control in a healthy population (2006) Am J Physiol Heart Circ Physiol, 290 (6), pp. H2560-H2570; 
Kuo, T.B., Yang, C.C., Sexual dimorphism in the complexity of cardiac pacemaker activity (2002) Am J Physiol Heart Circ Physiol, 283 (4), pp. H1695-H1702; 
Groome, L.J., Mooney, D.M., Holland, S.B., Smith, L.A., Atterbury, J.L., Dykman, R.A., Behavioral state affects heart rate response to low-intensity sound in human fetuses (1999) Early Hum Dev, 54 (1), pp. 39-54; 
Fleisher, L.A., Dipietro, J.A., Johnson, T.R., Pincus, S., Complementary and non-coincident increases in heart rate variability and irregularity during fetal development (1997) Clin Sci (Lond), 92 (4), pp. 345-349; 
Bernardes, J., Costa-Pereira, A., Ayres-de-Campos, D., van Geijn, H.P., Pereira-Leite, L., Evaluation of interobserver agreement of cardiotocograms (1997) Int J Gynecol Obstet, Suppl, 57 (1), pp. 33-37; 
Ayres-de-Campos, D., Bernardes, J., Costa-Pereira, A., Pereira-Leite, L., Inconsistencies in expert{\textquoteright}s classification of cardiotocograms and subsequent clinical decision (1999) Br J Obstet Gynecol, 106, pp. 1307-1310; 
Bernardes, J., Moura, C., Marques-de-S{\'a}, J.P., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J Perinat Med, 19, pp. 61-65; 
Bernardes, J., Ayres-de-Campos, D., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int J Gynaecol Obstet, 62 (2), pp. 141-147; 
Ayres-de-Campos, D., Costa-Santos, C., Bernardes, J., SisPorto Multicentre Validation Study Group. Prediction of neonatal state by computer analysis of fetal heart rate tracings: the antepartum arm of the SisPorto multicentre validation study (2005) Eur J Obstet Gynecol Reprod Biol, 118 (1), pp. 52-60; 
Dawes, G.S., Moulden, M., Redman, C.W., Improvements in computerized fetal heart rate analysis antepartum (1996) J Perinat Med, 24 (1), pp. 25-36
},
	month = {2008///},
	pages = {433 - 439},
	abstract = {Background: A better understanding of gender influences on fetal heart rate can help to improve analysis of the latter and perhaps elucidate the increased risk of perinatal death that occurs in males. Aim: To assess differences in linear and complex heart rate dynamics according to fetal sex, in the antepartum period of normal term pregnancies, for patterns associated with fetal behavioural states. Study design and subjects: One hundred and eighty seven fetal heart rate segments of 10-minute duration, acquired with a system for computerized analysis of cardiotocograms and classified into fetal behavioural patterns A, B, C or D were analysed. They had been acquired from 24 female and 23 male term fetuses, with uneventful perinatal outcomes. Four different comparative studies between female and male fetuses were conducted, considering different adjustments for gestational age, weight and FHR pattern. Outcome measures: Indices of linear and nonlinear fetal heart rate variability, namely, long-term irregularity index, very low, low and high frequency spectral indices, approximate entropy and sample entropy. Results: Pattern B was the most frequent, both in female and male fetuses. Pattern A was more likely to be associated to female than male fetuses, whereas the opposite occurred with patterns C and D. Linear indices were significantly higher in male than in female fetuses, whereas the opposite occurred with nonlinear indices. Conclusions: Male fetuses exhibited significantly more linear and significantly less complex fetal heart rate activity than female fetuses, expressing signs of a more active autonomous nervous system and of less active complexity control systems. These aspects may need to be considered when interpreting FHR tracings. {\textcopyright} 2007 Elsevier Ireland Ltd. All rights reserved.},
	keywords = {article, Behavior, Cardiotocography, comparative study, Computerized analysis, Entropy and spectral analysis, Female, Fetal behavioural states and sex, Fetal heart rate, Fetal monitoring, Fetal Movement, fetus, fetus heart rate, Gestational Age, heart hemodynamics, Heart Rate, Fetal, human, Humans, male, normal human, Pregnancy, Pregnancy Outcome, Sex Characteristics, sex difference, SisPorto},
	isbn = {03783782 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-44749091847\&partnerID=40\&md5=0a0fcbbe86dcad0bee063b6cc7687573},
	author = {Bernardes, J. and Gon{\c c}alves, H. and Ayres-de-Campos, D. and Rocha, A.P.}
}
@article {2339,
	title = {Linear and nonlinear heart-rate analysis in a rat model of acute anoxia},
	journal = {Physiological MeasurementPhysiol. Meas.},
	volume = {29},
	year = {2008},
	note = {Cited By (since 1996): 6Export Date: 21 November 2012Source: ScopusCODEN: PMEAEdoi: 10.1088/0967-3334/29/9/010PubMed ID: 18784391Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade Do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptReferences: American College of Obstetricians and Gynecologists. ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists, Number 70, December 2005 (2005) Obstet. Gynecol., 106, pp. 1453-1460;Ayres-De-Campos, D., Bernardes, J., Garrido, A., Marques-De-S{\'a}, J., Pereira-Leite, L., SisPorto 2.0: A program for automated analysis of cardiotocograms (2000) J. Mat. Fet. Med., 9 (5), pp. 311-318; 
Ayres-De-Campos, D., Santos, C., Bernardes, J., Prediction of neonatal state by computer analysis of fetal heart rate tracings: The antepartum arm of the SisPorto{\textregistered} validation study (2005) Eur. J. Obstet. Gynecol. Reprod. Biol., 118 (1), pp. 52-60; 
Beckers, F., Verheyden, B., Aubert, A.E., Aging and nonlinear heart rate control in a healthy population (2006) Am. J. Physiol. Heart Circ. Physiol., 290 (6), pp. 2560-H2570; 
Beckers, F., Verheyden, B., Ramaekers, D., Swinghedauw, B., Aubert, A.E., Effects of autonomic blockade on non-linear cardiovascular variability indices in rats (2006) Clin. Exp. Pharmacol. Physiol., 33 (5-6), pp. 431-439; 
Bernardes, J., Ayres-De-Campos, D., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int. J. Gynecol. Obstet., 62 (2), pp. 141-147; 
Bernardes, J., Moura, C., Marques-De-S{\'a}, J.P., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J. Perinat. Med., 19, pp. 61-65; 
Cerutti, C., Gustin, M.P., Paultre, C.Z., Lo, M., Julien, C., Vincent, M., Sassard, J., Autonomic nervous-system and cardiovascular variability in rats-a spectral-analysis approach (1991) Am. J. Physiol., 261, pp. 1292-H1299; 
Chaffin, D.G., Barnard, J.M., Phernetton, T., Reed, K.L., Decreased approximate entropy of heart rate variability in the hypoxic ovine fetus (1998) J. Matern. Fetal Invest., 8, pp. 23-26; 
Dudewicz, E., Mishra, S., (1988) Modern Mathematical Statistics; 
Felgueiras, C., Marques-De-S{\'a}, J.P., Bernardes, J., Gama, S., Fractal characterisation of fetal heart rate sequences (1998) Biomedical Eng., 36, pp. 197-201; 
Gon{\c c}alves, H., Bernardes, J., Rocha, A.P., Ayres-De-Campos, D., Linear and nonlinear analysis of heart rate patterns associated with fetal behavioral states in the antepartum period (2007) Early Human Develop., 83 (9), pp. 585-591; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-De-Campos, D., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters (2006) Physiol. Meas., 27 (3), pp. 307-319; 
Gon{\c c}alves, H., Rocha, A.P., Ayres-De-Campos, D., Bernardes, J., Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery (2006) Med. Biol. Eng. Comput., 44 (10), pp. 847-855; 
Hayes, M., (1996) Statistical Digital Signal Processing and Modelling; 
Henriques-Coelho, T., Correia-Pinto, J., Roncon-Albuquerque, R., Baptista, M.J., Lourenco, A.P., Oliveira, S.M., Brandao-Nogueira, A., Leite-Moreira, A.F., Endogenous production of ghrelin and beneficial effects of its exogenous administration in monocrotaline-induced pulmonary hypertension (2004) Am. J. Physiol. Heart Circ. Physiol., 287 (6), pp. 2885-H2890; 
Kuwahara, M., Yayou, K., Ishii, K., Hashimoto, S., Tsubone, H., Sugano, S., Power spectral analysis of heart rate variability as a new method for assessing autonomic activity in the rat (1994) J. Electrocardiology, 27 (4), pp. 333-337; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Wu, G., Shen, L., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) Eur. J. Obstet. Gynecol. Reprod. Biol., 114 (2), pp. 137-143; 
Louren{\c c}o, A.P., Roncon-Albuquerque, R., Bras-Silva, C., Faria, B., Wieland, J., Henriques-Coelho, T., Correia-Pinto, J., Leite-Moreira, A.F., Myocardial dysfunction and neurohumoral activation without remodeling in left ventricle of monocrotaline-induced pulmonary hypertensive rats (2006) Am. J. Physiol. Heart Circ. Physiol., 291 (4), pp. 1587-H1594; 
Magenes, G., Signorini, M.G., Arduini, D., Classification of cardiotocographic records by neural networks (2000) IJCNN 2000: Proc. IEEE-INNS-ENNS Int. Joint Conf. on Neural Network, 3, pp. 637-641; 
Martinez, W.L., Martinez, A.R., (2002) Computational Statistics Handbook with MATLAB; 
Moraru, L., Cimponeriu, L., Tong, S., Thakor, N., Bezerianos, A., Characterization of heart rate variability changes following asphyxia in rats (2004) Methods Inf. Med., 43 (1), pp. 118-121; 
Moraru, L., Tong, S., Malhotra, A., Geocadin, R., Thakor, N., Bezerianos, A., Investigation of the effects of ischemic preconditioning on the HRV response to transient global ischemia using linear and nonlinear methods (2005) Med. Eng. Phys., 27 (6), pp. 465-473; 
Murasato, Y., Hirakawa, H., Harada, Y., Nakamura, T., Hayashida, Y., Effects of systemic hypoxia on R-r interval and blood pressure variabilities in conscious rats (1998) Am. J. Physiol., 275, pp. 797-H804; 
Niklasson, U., Wiklund, U., Bjerle, P., Olofsson, B.O., Heart-rate variation-what are we measuring? (1993) Clin. Physiol., 13 (1), pp. 71-79; 
Pincus, S., Aproximate entropy (ApEn) as a complexity measure (1995) Chaos, 5 (1), pp. 110-117; 
Pincus, S.M., Gevers, E.F., Robinson, I.C.A.F., Vandenberg, G., Roelfsema, F., Hartman, M.L., Veldhuis, J.D., Females secrete growth hormone with more process irregularity than males in both humans and rats (1996) Am. J. Physiol., 270, pp. 107-E115; 
Pincus, S., Viscarello, R., Approximate Entropy: A regularity measure for fetal heart rate analysis (1992) Obstet. Gynecol., 79, pp. 249-255; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am. J. Physiol. Heart Circ. Physiol., 278, pp. 2039-H2049; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans. Biomed. Eng., 50 (3), pp. 365-373; 
Siira, S.M., Ojala, T.H., Vahlberg, T.J., Jalonen, J.O., Valimaki, I.A., Rosen, K.G., Ekholm, E.M., Marked fetal acidosis and specific changes in power spectrum analysis of fetal heart rate variability recorded during the last hour of labour (2005) BJOG, 112 (4), pp. 418-423; 
Task force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, Heart rate variability-standards of measurement, physiological interpretation and clinical use (1996) Circulation, 93, pp. 1043-1065; 
Vieira, P., Marques-De-S{\'a}, J.P., Bernardes, J., Fractal analysis of foetal heart rate (2004) Proc. Biosignal 2004, pp. 53-55
},
	month = {2008///},
	pages = {1133 - 1143},
	abstract = {The objective of this study was the assessment of heart-rate (HR) dynamics with linear and nonlinear methods during episodes of mechanical ventilation and acute anoxia in rats. Namely, to assess whether linear and nonlinear HR analysis was able to discriminate acute anoxia from baseline in rats and if this was consistent with human foetal and adult studies. Five HR segments of 1 min duration, during baseline recording, mechanical ventilation and first, second and third minutes of induced acute anoxia, were analysed in ten adult Wistar rats. Linear time and frequency domain and nonlinear methods were used, namely mean HR (mHR), long-term irregularity (LTI), interval index (II), low frequency (LF) and high frequency (HF), approximate entropy (ApEn) and sample entropy (SampEn). New parameters for the entropy indices are proposed for the analysis of rats{\textquoteright} HR. Bootstrap percentile confidence intervals and nonparametric statistical tests were used in the evaluation of the differences between segments. During mechanical ventilation a clear spectral band was detectable at the ventilation rate, but mHR, II and the {\textquoteright}new{\textquoteright} entropy indices were the only significantly changed indices. In the transition from baseline-mechanical- ventilation to mechanical-ventilation-induced anoxia, a statistically significant decrease of mHR, II and entropy indices was observed, clearly discriminating these two instances, whereas most linear indices increased. With continued anoxia, most linear indices decreased significantly, whereas entropy remained stably low. These results are consistent with other foetal human and non-human studies and evidence that the rat model may be used for further research on linear and nonlinear analysis of heart-rate dynamics. The transition from baseline to acute anoxia was encompassed by signs of increased activation of the autonomic nervous system sympathetic branch, and decreased or blunted activity of the HR complexity regulatory centres. {\textcopyright} 2008 Institute of Physics and Engineering in Medicine.},
	keywords = {acute disease, animal experiment, animal model, Animals, Anoxia, article, artificial ventilation, bootstrapping, controlled study, entropy, Female, Fetal monitoring, frequency analysis, Heart rate, Heart rate variability, Humans, Linear analysis, linear system, lung ventilation, Models, Cardiovascular, nonhuman, nonlinear system, priority journal, rat, Rats, Rats, Wistar, Rattus, Rattus norvegicus, Respiration, Artificial, Statistical analysis, Variability, Wistar rat, Wistar rats},
	isbn = {09673334 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-51849120545\&partnerID=40\&md5=56be327bb0d959060a2f4a0f080ae264},
	author = {Gon{\c c}alves, H. and Henriques-Coelho, T. and Bernardes, J. and Rocha, A.P. and Nogueira, A. and Leite-Moreira, A.}
}
@article {2419,
	title = {Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters},
	journal = {Physiological MeasurementPhysiol. Meas.},
	volume = {27},
	year = {2006},
	note = {Cited By (since 1996): 15Export Date: 21 November 2012Source: ScopusCODEN: PMEAEdoi: 10.1088/0967-3334/27/3/008PubMed ID: 16462016Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade Do Porto, Porto, Portugal; email: hernani.goncalves@fc.up.ptReferences: Ayres-De-Campos, D., Bernardes, J., Garrido, A., Marques-De-S{\'a}, J., Pereira-Leite, L., SisPorto 2.0: A program for automated analysis of cardiotocograms (2000) J. Matern. Fetal Med., 9 (5), pp. 311-318;Ayres-De-Campos, D., Bernardes, J., Reynolds, A., Saraiva, J.P., Santos, C., Pereira-Leite, L., Computer evaluation of internal versus external FHR monitoring in the minutes preceding delivery (2000) Int. J. Gynecol. Obstet., 70, pp. 60-B61; 
Ayres-De-Campos, D., Santos, C., Bernardes, J., Prediction of neonatal state by computer analysis of fetal heart rate tracings: The antepartum arm of the SisPorto {\textregistered}multicentre validation study (2005) Eur. J. Obstet. Gynecol. Reprod. Biol., 118 (1), pp. 52-60; 
Bakker, P.C., Colenbrander, G.J., Verstraeten, A.A., Geijn, V., The quality of intrapartum fetal heart rate monitoring (2004) Eur. J. Obstet. Gynecol. Reprod. Biol., 116 (1), pp. 22-27; 
Bernardes, J., Ayres-De-Campos, D., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int. J. Gynecol. Obstet., 62 (2), pp. 141-147; 
Bernardes, J., Costa-Pereira, A., The effect of different sampling intervals on the measurement of intrapartum fetal heart rate variability (1997) Obstet. Gynecol., 90 (2), pp. 318-319; 
Bernardes, J., Garrido, A., Computerized fetal heart rate analysis in labour based on 2-s sampling. Can it proceed with confidence? (1995) Eur. J. Obstet. Gynecol. Reprod. Biol., 63 (1), pp. 105-107; 
Bernardes, J., Moura, C., Marques-De-S{\'a}, J.P., Pereira-Leite, L., The Porto system for automated cardiotocographic signal analysis (1991) J. Perinat. Med., 19, pp. 61-65; 
Bernardes, J., Moura, C., Marques-De-S{\'a}, J.P., Van Geijn, H.P., Pereira-Leite, L., The Porto system (1994) A Critical Appraisal of Fetal Surveillance, pp. 315-324; 
Boog, G., Analyse informatis{\'e}e du rythme cardiaque fetal au cours de la grosssesse et de l{\textquoteright}accouchement (2004) Encyclop{\'e}die M{\'e}dico-Chirurgicale, 148; 
Boos, A., Jagger, M.H., Paret, G.W., Hausmann, J.W., A new, lightweight fetal telemetry system (1995) Hewlett-Packard J., pp. 82-93; 
Carter, M.C., Signal processing and display-cardiotocographs (1993) Br. J. Obstet. Gynaecol., 100, pp. 21-23; 
Chaffin, D.G., Barnard, J.M., Phernetton, T., Reed, K.L., Decreased approximate entropy of heart rate variability in the hypoxic ovine fetus (1998) J. Matern. Fetal Invest., 8, pp. 23-26; 
Chang, A., Sahota, D.S., Reed, N.N., James, D.K., Mohajer, M.P., Computerised fetal heart rate analysis in labour-effect of sampling rate (1995) Eur. J. Obstet. Gynecol. Reprod. Biol., 59 (2), pp. 125-129; 
Court, D.J., Parer, J.T., Experimental studies of fetal asphyxia and fetal heart rate interpretation (1984) Research in Perinatal Medicine, pp. 113-169; 
Dawes, G., Computerized fetal heart rate analysis (1994) A Critical Appraisal of Fetal Surveillance, pp. 311-314; 
Dawes, G.S., Moulden, M., Sheil, O., Redman, C.W.G., Approximate entropy, a statistic of regularity, applied to fetal heart rate data before and during labour (1992) Obstet. Gynecol., 80, pp. 763-768; 
Dawes, G.S., Moulden, M., Redman, C.W., Criteria for the design of fetal heart rate analysis systems (1990) Int. J. Biomed. Comput., 25 (4), pp. 287-294; 
Di Renzo, G.C., Montani, M., Fioriti, V., Clerici, G., Branconi, F., Pardini, A., Indraccolo, R., Cosmi, E.V., Fractal analysis: A new method for evaluating fetal heart rate variability (1996) J. Perinat. Med., 24, pp. 261-269; 
Echeverria, J.C., Hayes-Gill, B.R., Crowe, J.A., Woolfson, M.S., Croaker, G.D., Detrended fluctuation analysis: A suitable method for studying fetal heart rate variability? (2004) Physiol. Meas., 25 (3), pp. 763-774; 
Felgueiras, C., Marques-De-S{\'a}, J.P., Bernardes, J., Gama, S., Fractal characterisation of fetal heart rate sequences (1998) Biomed. Eng., 36, pp. 197-201; 
Felgueiras, C.S., Marques-De-S{\'a}, J.P., Bernardes, J., Gama, S., On the reconstruction of fetal heart rate sequences (1996) Actas Do 4{\textdegree} Congresso Portugu{\^e}s de Engenharia Biom{\'e}dica-BioEng{\textquoteright}96, pp. 61-vii65; 
Fukushima, T., Flores, C.A., Hon, E.H., Davidson Jr., E.C., Limitations of autocorrelation in fetal heart rate monitoring (1985) Am. J. Obstet. Gynecol., 153, pp. 685-692; 
Fusheng, Y., Bo, H., Qingyu, T., Approximate entropy and its application in biosignal analysis (1998) Nonlinear Biomedical Signal Processing-Volume II: Dynamical Analysis and Modelling, pp. 72-91; 
Gough, N.A., Fractal analysis of fetal heart rate variability (1993) Physiol. Meas., 14 (3), pp. 309-315; 
Hayes, M., (1996) Statistical Digital Signal Processing and Modelling; 
Hewlett-Packard, (1993) Hewlett-Packard Series 50 Service Manual, M1351A and 1353A; 
Hirsch, M., Karin, J., Akselrod, S., Heart rate variability in the fetus (1995) Heart Rate Variability, pp. 517-531; 
Lawson, G.W., Belcher, R., Dawes, G.S., Redman, C.W., A comparison of ultrasound (with autocorrelation) and direct electrocardiogram fetal heart rate detector systems (1983) Am. J. Obstet. Gynecol., 147, pp. 721-722; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Wu, G., Shen, L., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) Eur. J. Obstet. Gynecol. Reprod. Biol., 114 (2), pp. 137-143; 
Lunghi, F., Magenes, G., Pedrinazzi, L., Signorini, M.G., Detection of fetal distress through a support vector machine based on fetal heart rate parameters (2005) Comput. Cardiol., 32, pp. 247-250; 
Magenes, G., Signorini, M.G., Arduini, D., Classification of cardiotocographic records by neural networks (2000) IJCNN 2000: Proc. IEEE-INNS-ENNS Int. Joint Conf. on Neural Networks, pp. 637-641; 
Electronic fetal heart rate monitoring: Research guidelines for interpretation (1997) Am. J. Obstet. Gynecol., 177 (6), pp. 1385-1390; 
Nijhuis, I., Ten Hof, J., Development of fetal heart rate and behavior: Indirect measures to assess the fetal nervous system (1999) Eur. J. Obstet. Gynecol. Reprod. Biol., 87 (1), pp. 1-2; 
Oppenheimer, L.W., Lewinsky, R.M., Power spectral analysis of fetal heart rate (1994) Baillieres Clin. Obstet. Gynaecol., 8, pp. 643-661; 
Peters, C.H., Ten Broeke, E.D., Andriessen, P., Vermeulen, B., Berendsen, R.C., Wijn, P.F., Oei, S.G., Beat-to-beat detection of fetal heart rate: Doppler ultrasound cardiotocography compared to direct ECG cardiotocography in time and frequency domain (2004) Physiol. Meas., 25 (2), pp. 585-593; 
Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc. Natl. Acad. Sci. USA, 88, pp. 2297-2301; 
Pincus, S., Approximate entropy (ApEn) as a complexity measure (1995) Chaos, 5 (1), pp. 110-117; 
Pincus, S., Viscarello, R., Approximate entropy: A regularity measure for fetal heart rate analysis (1992) Obstet. Gynecol., 79, pp. 249-255; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am. J. Physiol. Heart Circ. Physiol., 278, pp. 2039-H2049; 
Salamalekis, E., Thomopoulos, P., Giannaris, D., Salloum, I., Vasios, G., Prentza, A., Koutsouris, D., Computerised intrapartum diagnosis of fetal hypoxia based on fetal heart rate monitoring and fetal pulse oximetry recordings utilising wavelet analysis and neural networks (2002) BJOG, 109 (10), pp. 1137-1142; 
Signorini, M., Cerutti, S., Nonlinear properties of Cardiovascular Time Series (1999) Methodology and Clinical Applications of Blood Pressure and Heart Rate Analysis, pp. 73-89; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans. Biomed. Eng., 50 (3), pp. 365-373; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Yaegashi, N., Murotsuki, J., Uehara, S., Yajima, A., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am. J. Obstet. Gynecol., 182 (5), pp. 1227-1232; 
Heart rate variability. Standards of measurement, physiological interpretation, and clinical use (1996) Eur. Heart J., 17, pp. 354-381; 
Wilcox, M.A., Wang, W., Sahota, D.S., Dawkins, R.R., Chung, T.K., Chang, A.M., The effect of different sampling intervals on the measurement of intrapartum fetal heart rate variability (1997) Obstet. Gynecol., 89 (4), pp. 577-580; 
Yum, M.K., Kim, K., Kim, J.H., Park, E.Y., A consistent abnormality in the average local smoothness of fetal heart rate in growth-restricted fetuses affected by severe pre-eclampsia (2004) Hypertens. Res., 27 (12), pp. 911-918
},
	month = {2006///},
	pages = {307 - 319},
	abstract = {The effect of foetal heart rate (FHR) acquisition mode on linear and nonlinear parameters is still largely unknown. In 33 normal labouring women, FHR signals were acquired simultaneously by an external ultrasound sensor applied to the maternal abdomen and an internal scalp electrode, in the minutes preceding delivery. For each case, the initial and final 5, 10 and 20 min segments were analysed, considering FHR signals at a frequency of 4 Hz (the frequency at which they are transmitted by the majority of commercialized foetal monitors). Several time and frequency domain linear and nonlinear FHR indices were computed in these segments, namely mean FHR, very low frequency (VLF), low frequency (LF), high frequency (HF), approximate entropy (ApEn) and sample entropy (SampEn). Parametric confidence intervals, statistical tests and correlation coefficients were calculated in order to evaluate the effect of internal versus external FHR monitoring modes on the considered indices. The whole evaluation was repeated using FHR signals at a frequency of 2 Hz. Most time domain linear indices were similar with external and internal monitoring in the initial and final segments of the tracings. However, linear frequency domain indices were poorly correlated in the final segments and had significantly different mean values in the initial segments. Nonlinear indices were significantly different in both initial and final segments. The correlation between 4 and 2 Hz sampled parameters was high for both linear and nonlinear indices (most correlation coefficient values ranging between 0.95 and 1) but nonlinear index values were significantly higher at 2 Hz. In conclusion, the mode used to acquire FHR signals and the sampling rate employed can significantly affect most FHR indices. {\textcopyright} 2006 IOP Publishing Ltd.},
	keywords = {abdomen, Algorithms, article, Cardiotocography, commercial phenomena, Confidence interval, controlled study, correlation coefficient, delivery, Diagnosis, Computer-Assisted, Electrocardiography, electrode, entropy, External and internal monitoring, Female, fetus electrocardiography, fetus monitoring, Foetal heart rate (FHR), Frequency domain analysis, Heart, Heart rate, human, intermethod comparison, intrapartum care, Linear and nonlinear analysis, Linear Models, mathematical computing, Nonlinear Dynamics, normal human, priority journal, Reproducibility of Results, sensitivity and specificity, sensor, Signal Processing, Computer-Assisted, Statistical significance, ultrasound, Variability},
	isbn = {09673334 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-32144438860\&partnerID=40\&md5=dd6dbb9f364b7f974c7048c4cf08d53f},
	author = {Gon{\c c}alves, H. and Rocha, A.P. and Ayres-de-Campos, D. and Bernardes, J.}
}
@article {2400,
	title = {Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery},
	journal = {Medical and Biological Engineering and ComputingMed. Biol. Eng. Comput.},
	volume = {44},
	year = {2006},
	note = {Cited By (since 1996): 20Export Date: 21 November 2012Source: ScopusCODEN: MBECDdoi: 10.1007/s11517-006-0105-6PubMed ID: 16988896Language of Original Document: EnglishCorrespondence Address: Gon{\c c}alves, H.; Departamento de Matem{\'a}tica Aplicada, Faculdade de Ci{\^e}ncias, Universidade do Porto, Rua do Campo Alegre - 687, 4169-007 Porto, Portugal; email: hernani.goncalves@fc.up.ptChemicals/CAS: AcidsReferences: ACOG technical bulletin. Fetal heart rate patterns: Monitoring, interpretation, and management (1995) Int J Gynecol Obstet, 51, pp. 65-74. , ACOG;Ayres-de-Campos, D., Bernardes, J., Costa-Pereira, A., Pereira-Leite, L., Inconsistencies in expert{\textquoteright}s classification of cardiotocograms and subsequent clinical decision (1999) Br J Obstet Gynecol, 106, pp. 1307-1310; 
Ayres-de-Campos, D., Bernardes, J., Garrido, A., de S{\'a}, J.M., Pereira-Leite, L., Sisporto 2.0: A program for automated analysis of cardiotocograms (2000) J Mat Fet Med, 9, pp. 311-318; 
Bernardes, J., de Campos, D.A., Costa-Pereira, A., Pereira-Leite, L., Garrido, A., Objective computerized fetal heart rate analysis (1998) Int J Gynecol Obstet, 62, pp. 141-147; 
Bernardes, J., Costa-Pereira, A., de Campos, D.A., van Geijn, H.P., Pereira-Leite, L., Evaluation of interobserver agreement of cardiotocograms (1997) Int J Gynecol Obstet, 57 (1), pp. 33-37; 
Bernardes, J., Moura, C., de S{\'a}, J.P.M., Pereira-Leite, L., The porto system for automated cardiotocographic signal analysis (1991) J Perinat Med, 19, pp. 61-65; 
Boog, G., Analyse informatisTe du rythme cardiaque foetal au cours de la grossesse et de l{\textquoteright}accouchement (2004) EncyclopTdie MTdico-Chirurgicale, 148, pp. 1-10. , (5-049-D-23); 
Carter, M.C., Signal processing and display - Cardiotocographs (1993) Br J Obstet Gynaecol, 100 (9), pp. 21-23; 
Chaffin, D.G., Barnard, J.M., Phernetton, T., Reed, K.L., Decreased approximate entropy of heart rate variability in the hypoxic ovine fetus (1998) J Matern Fetal Invest, 8, pp. 23-26; 
Chung, D.Y., Sim, Y.B., Park, K.T., Yi, S.H., Shin, J.C., Kim, S.P., Spectral analysis of fetal heart rate variability as a predictor of intrapartum fetal distress (2001) Int J Gynecol Obstet, 73, pp. 109-116; 
Colenbrander, G.J., van Geijn, H.P., Goovaerts, H.G., Acquisition of fetal heart rate signals (1994) A Critical Appraisal of Fetal Surveillance, pp. 203-210. , In: Geijn HPV, Copray FJA (eds) Elsevier Science, Amsterdam; 
Dawes, G.S., Moulden, M., Sheil, O., Redman, C.W.G., Approximate entropy, a statistic of regularity, applied to fetal heart rate data before and during labour (1992) Obstet Gynecol, 80 (5), pp. 763-768; 
Dudewicz, E., Mishra, S., (1988) Modern Mathematical Statistics, , Wiley, New York; 
Echeverrfa, J.C., Hayes-Gill, B.R., Crowe, J.A., Woolfson, M.S., Croaker, G.D.H., Detrended fluctuation analysis: A suitable method for studying fetal heart rate variability? (1990) Int J Biomed Comput, 25, pp. 287-294; 
Felgueiras, C., de S{\'a}, J.P.M., Bernardes, J., Gama, S., Fractal characterisation of fetal heart rate sequences (1998) Biomed Eng, 36 (2), pp. 197-201; 
Fusheng, Y., Bo, H., Qingyu, T., Approximate entropy and its application in biosignal analysis (1998) Nonlinear Biomedical Signal Processing. Dynamical Analysis and Modelling, 2, pp. 72-91. , In: Akay M (ed) IEEE Press, New York; 
Gon{\c c}alves, H., Rocha, A.P., de Campos, D.A., Bernardes, J., Internal versus external intrapartum foetal heart rate monitoring: The effect on linear and nonlinear parameters (2006) Physiol Meas, 27, pp. 307-319; 
Gough, N.A., Fractal analysis of foetal heart rate variability (1993) Physiol Meas, 14 (3), pp. 309-315; 
Hayes, M., (1996) Statistical Digital Signal Processing and Modelling, , Wiley, New York; 
Hewlett-Packard, (1993) Hewlett-Packard Series 50 Service Manual, , M1351A and 1353A. Germany; 
King, T., Parer, J., The physiology of fetal heart rate patterns and perinatal asphyxia (2000) J Perinat Neonat Nurs, 14 (3), pp. 19-39; 
Li, X., Tang, D., Zhou, S., Zhou, G., Wang, C., Zhuang, Y., Wu, G., Shen, L., Redistribution of power spectrum of heart rate variability during acute umbilical artery embolism and hypoxemia in late-gestation fetal sheep (2004) Eur J Obstet Gynecol Reprod Biol, 114, pp. 137-143; 
Magenes, G., Signorini, M.G., Arduini, D., Classification of cardiotocographic records by neural networks (2000) Proceedings of the IEEE-INNS-ENNS International Joint Conference on Neural Networks,, 3, pp. 637-641. , In: IJCNN 2000; 
Martin, J.C.B., Electronic fetal monitoring: A brief summary of its development, problems and prospects (1998) Eur J Obstet Gynecol Reprod Biol, 78, pp. 133-140; 
Martinez, W.L., Martinez, A.R., (2002) Computational Statistics Handbook With MATLAB, , CRC Press, Boca Raton; 
Oppenheimer, L.W., Lewinsky, R.M., Power spectral analysis of fetal heart rate (1994) Baillieres Clin Obstet Gynaecol, 8 (3), pp. 643-661; 
Pincus, S., Approximate entropy as a measure of system complexity (1991) Proc Natl Acad Sci USA, 88, pp. 2297-2301; 
Pincus, S., Approximate entropy (apen) as a complexity measure (1995) Chaos, 5 (1), pp. 110-117; 
Pincus, S., Viscarello, R., Approximate entropy: A regularity measure for fetal heart rate analysis (1992) Obstet Gynecol, 79 (2), pp. 249-255; 
di Renzo, G.C., Montani, M., Fioriti, V., Clerici, G., Branconi, F., Pardini, A., Indraccolo, R., Cosmi, E.V., Fractal analysis: A new method for evaluating fetal heart rate variability (1996) J Perinat Med, 24 (3), pp. 261-269; 
Richman, J.S., Moorman, J.R., Physiological time-series analysis using approximate entropy and sample entropy (2000) Am J Physiol Heart Circ Physiol, 278, pp. H2039-H2049; 
Ripley, B.D., (1996) Pattern Recognition and Neural Networks, , Cambridge University Press, London; 
Rooth, G., Huch, A., Huch, R., FIGO news. Guidelines for the use of fetal monitoring (1987) Int J Gynecol Obstet, 25, p. 159; 
(2001) Evidence-Based Clinical Guideline Number 8. The Use of Electronic Fetal Monitoring, , Royal College of Obstetricians and Gynaecologists Royal College of Obstetricians and Gynaecologists, London; 
Salamalekis, E., Thomopoulos, P., Giannaris, D., Salloum, I., Vasios, G., Prentza, A., Koutsouris, D., Computerised intrapartum diagnosis of fetal hypoxia based on fetal heart rate monitoring and fetal pulse oximetry recordings utilising wavelet analysis and neural networks (2002) BJOG, 109 (10), pp. 1137-1142; 
Signorini, M.G., Cerutti, S., Nonlinear properties of cardiovascular time series (1999) Methodology and Clinical Applications of Blood Pressure and Heart Rate Analysis, pp. 73-89. , In: Di Rienzo M, Mancia G, Parati G, Pedotti A, Zanchetti A (eds) IOS Press, Amsterdam; 
Signorini, M.G., Magenes, G., Cerrutti, S., Arduini, D., Linear and nonlinear parameters for the analysis of fetal heart rate signal from cardiotacographic recordings (2003) IEEE Trans Biomed Eng, 50 (3), pp. 365-373; 
Siira, S.M., Ojala, T.H., Vahlberg, T.J., Jalonen, J.O., Valimaki, I.A., Rosen, K.G., Ekholm, E.M., Marked fetal acidosis and specific changes in power spectrum analysis of fetal heart rate variability recorded during the last hour of labour (2005) Br J Obstet Gynaecol, 112, pp. 418-423; 
Suzuki, T., Okamura, K., Kimura, Y., Watanabe, T., Murotsuki, N.Y.J., Uehara, S., Yajima, A., Power spectral analysis of R-R interval variability before and during the sinusoidal heart rate pattern in fetal lambs (2000) Am J Obstet Gynecol, 182, pp. 1227-1232; 
Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Task force of the european society of cardiology and the north american society of pacing and electrophysiology (1996) Eur Heart J, 17, pp. 354-381. , Task-Force; 
Teich, M.C., Lowen, S.B., Jost, B.M., Vibe-Rheymer, K., Heneghan, C., Heart rate variability: Measures and models (1998) Nonlinear Biomedical Signal Processing. Dynamic Analysis and Modeling, 2, pp. 159-213. , In: Akay M (ed) IEEE Press, New York; 
Yum, M.K., Kim, K., Kim, J.H., Park, E.Y., A consistent abnormality in the average local smoothness of fetal heart rate in growth-restricted fetuses affected by severe pre-eclampsia (2004) Hypertens Res, 27 (12), pp. 911-918
},
	month = {2006///},
	pages = {847 - 855},
	abstract = {Linear and nonlinear fetal heart rate (FHR) indices, namely mean FHR, interval index (II), very low, low and high frequencies, approximate (ApEn) and sample entropy (SampEn), were computed, immediately before delivery, in the initial and final FHR tracing segments, from 48 normal, 10 mildly acidemic and 10 moderate-to-severely acidemic fetuses. Progression of labor was associated with a significant increase in linear frequency domain indices whereas nonlinear indices were significantly decreased. Moderate-to-severe fetal acidemia was associated with a significant decrease in nonlinear indices. The best discrimination between moderate-to-severe acidemic fetuses and the remaining cases was obtained combining II and ApEn(2,0.15), with a specificity of 71\% and a sensitivity of 80\%. These findings support the hypothesis of increased autonomic nervous system activity in the final minutes of labor and of decreased central nervous system activity, both in the final minutes of labor and in moderate-to-severe acidemic fetuses. {\textcopyright} International Federation for Medical and Biological Engineering 2006.},
	keywords = {acidemia, Acidosis, Acids, article, autonomic nervous system, Biological materials, Cardiology, Central nervous system, clinical article, controlled study, delivery, Delivery, Obstetric, Discriminant Analysis, disease severity, entropy, Fetal Diseases, Fetal heart rate, Fetal heart rate (FHR), Fetal monitoring, fetus, fetus heart rate, Frequency domain analysis, Heart Rate, Fetal, human, Humans, hypothesis, labor, Linear and nonlinear indices, linear system, Neurology, newborn, nonlinear system, Prenatal Care, Second stage of labor, sensitivity and specificity, Severity of Illness Index},
	isbn = {01400118 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-33749566759\&partnerID=40\&md5=88f9959edd8363f90b13742d0ce5221b},
	author = {Gon{\c c}alves, H. and Rocha, A.P. and Ayres-de-Campos, D. and Bernardes, J.}
}
