title: Dynamics of the heart rate variability and oxygen saturation response to acute normobaric hypoxia within the first 10 min of exposure.
abstract: Although the heart rate variability (HRV) response to hypoxia has been studied, little is known about the dynamics of HRV after hypoxia exposure. The purpose of this study was to assess the HRV and oxygen saturation (SpO2) responses to normobaric hypoxia (FiO2= 9·6%) comparing 1 min segments to baseline (normoxia). Electrocardiogram and SpO2were recorded during a 10-min hypoxia exposure in 29 healthy male subjects aged 26·0 ± 4·9 years. Baseline HRV values were obtained from a 5-min recording period prior to hypoxia. The hypoxia period was split into 10 non-overlapping 1-min segments and time domain HRV indexes (RMSSD and SDNN) were calculated for each segment. Differences (Δ) from baseline values were calculated and transformed using natural logarithm (Ln). This study revealed that the decrease in ΔSpO2became significant (P<0·001) in the first minute of hypoxia, the decrease in ΔLn RMSSD became significant (P = 0·002) in the second minute, and the decrease in ΔLn SDNN became significant (P = 0·001) in the third minute. Between the second and fifth minute of hypoxia, ΔSpO2correlated with ΔLn RMSSD (r = 0·57, P<0·001) and ΔLn SDNN (r = 0·44, P<0·001). Five min after the onset of hypoxia, ΔSpO2was significantly (P = 0·002) decreased but changes in ΔLn RMSSD (P = 0·344) and ΔLn SDNN (P = 0·558) were not significant. In conclusion, the decrease in HRV was proportional to desaturation but only during the first 5 min of hypoxia.
authors.affiliation: Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacký University Olomouc, Olomouc, Czech Republic.
authors.forename: Jakub
authors.initials: J
authors.lastname: Krejčí
authors.affiliation: Department of Natural Sciences in Kinanthropology, Faculty of Physical Culture, Palacký University Olomouc, Olomouc, Czech Republic.
authors.forename: Michal
authors.initials: M
authors.lastname: Botek
authors.affiliation: Discipline of Sport and Exercise Science, Faculty of Health, UC-Research Institute for Sport and Exercise, University of Canberra, Canberra, ACT, Australia.|Discipline of Biokinetics, Exercise and Leisure Sciences, School of Health Sciences, University of KwaZulu-Natal, Durban, South Africa.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: McKune
mesh_terms: D000064:Acclimatization; D000328:Adult; D000531:Altitude; D000532:Altitude Sickness / Q000097:blood* / Q000175:diagnosis / Q000503:physiopathology*; D001341:Autonomic Nervous System / Q000503:physiopathology*; D015415:Biomarkers / Q000097:blood; D004562:Electrocardiography; D006321:Heart / Q000294:innervation*; D006339:Heart Rate; D006801:Humans; D000860:Hypoxia / Q000097:blood* / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood*; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010100:Oxygen
keywords: autonomic nervous system; exponential decay; root mean square successive difference; simulated altitude; time domain