Vagal activity and oxygen saturation response to hypoxia

Effects of aerobic fitness and rating of hypoxia tolerance

Tomáš Macoun, Michal Botek, Jakub Krejčí, Andrew J. McKune

Research output: Contribution to journalArticle

1 Citation (Scopus)
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Abstract

Background: A reduction in the inspired oxygen fraction (FiO2) induces a decline in arterial oxygen saturation (SpO2) and changes of heart rate variability (HRV). It has been shown that SpO2 and HRV responses to similar levels of acute normobaric hypoxia are inter-individual variable. Variable response may be influenced by normoxia reached maximal oxygen uptake (VO2max) value. Objective: The primary aim was to assess HRV and the SpO2 response to hypoxia, and examine the association with normoxic VO2max. Methods: Supine HRV and SpO2 were monitored during normobaric hypoxia (FiO2 = 9.6%) for 10 minutes in 28 subjects, aged 23.7 ± 1.7 years. HRV was evaluated by using both spectral and time domain HRV analysis. Low frequency (LF, 0.05-0.15 Hz) and high frequency (HF, 0.15-0.50 Hz) power together with square root of the mean of the squares of the successive differences (rMSSD) were calculated and transformed by natural logarithm (Ln). Based on the SpO2 in hypoxia, subjects were divided into Resistant (RG, SpO2 ≥ 70.9%, n = 14) and Sensitive (SG, SpO2 < 70.9%, n = 14) groups. Perceived hypoxia tolerance was self-scored on a 4-level scale. Results: VO2max was higher in SG (62.4 ± 7.2 ml · kg-1 · min-1) compared with RG (55.5 ± 7.1 ml · kg-1 · min-1, p =.017, d = 0.97). A significant relationship (r = -.45, p =.017) between hypoxicnormoxic difference in SpO2 and normoxic VO2max level was found. Vagal activity (Ln rMSSD) was significantly decreased (SG: p <.001, d = 2.64; RG: p <.001, d = 1.22), while sympathetic activity (Ln LF/HF) was relatively increased (p <.001, d = -1.40) in only the SG during hypoxia. Conclusions: Results show that subjects with a higher aerobic capacity exhibited a greater decline in SpO2, accompanied by greater autonomic cardiac disturbances during hypoxia. The SpO2 reduction was associated with perceived hypoxia comfort/discomfort. The hypoxia discomfort state was accompanied by a greater withdrawal in cardiac vagal activity.

Original languageEnglish
Pages (from-to)112-121
Number of pages10
JournalActa Gymnica
Volume47
Issue number3
DOIs
Publication statusPublished - 1 Jan 2017

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Oxygen
Heart Rate
Hypoxia

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@article{cc7d20b653b44b4380983eaa9114d1e9,
title = "Vagal activity and oxygen saturation response to hypoxia: Effects of aerobic fitness and rating of hypoxia tolerance",
abstract = "Background: A reduction in the inspired oxygen fraction (FiO2) induces a decline in arterial oxygen saturation (SpO2) and changes of heart rate variability (HRV). It has been shown that SpO2 and HRV responses to similar levels of acute normobaric hypoxia are inter-individual variable. Variable response may be influenced by normoxia reached maximal oxygen uptake (VO2max) value. Objective: The primary aim was to assess HRV and the SpO2 response to hypoxia, and examine the association with normoxic VO2max. Methods: Supine HRV and SpO2 were monitored during normobaric hypoxia (FiO2 = 9.6{\%}) for 10 minutes in 28 subjects, aged 23.7 ± 1.7 years. HRV was evaluated by using both spectral and time domain HRV analysis. Low frequency (LF, 0.05-0.15 Hz) and high frequency (HF, 0.15-0.50 Hz) power together with square root of the mean of the squares of the successive differences (rMSSD) were calculated and transformed by natural logarithm (Ln). Based on the SpO2 in hypoxia, subjects were divided into Resistant (RG, SpO2 ≥ 70.9{\%}, n = 14) and Sensitive (SG, SpO2 < 70.9{\%}, n = 14) groups. Perceived hypoxia tolerance was self-scored on a 4-level scale. Results: VO2max was higher in SG (62.4 ± 7.2 ml · kg-1 · min-1) compared with RG (55.5 ± 7.1 ml · kg-1 · min-1, p =.017, d = 0.97). A significant relationship (r = -.45, p =.017) between hypoxicnormoxic difference in SpO2 and normoxic VO2max level was found. Vagal activity (Ln rMSSD) was significantly decreased (SG: p <.001, d = 2.64; RG: p <.001, d = 1.22), while sympathetic activity (Ln LF/HF) was relatively increased (p <.001, d = -1.40) in only the SG during hypoxia. Conclusions: Results show that subjects with a higher aerobic capacity exhibited a greater decline in SpO2, accompanied by greater autonomic cardiac disturbances during hypoxia. The SpO2 reduction was associated with perceived hypoxia comfort/discomfort. The hypoxia discomfort state was accompanied by a greater withdrawal in cardiac vagal activity.",
keywords = "Acute mountain sickness, Haemoglobin desaturation, Heart rate variability, Maximal oxygen uptake, Simulated altitude",
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Vagal activity and oxygen saturation response to hypoxia : Effects of aerobic fitness and rating of hypoxia tolerance. / Macoun, Tomáš; Botek, Michal; Krejčí, Jakub; McKune, Andrew J.

In: Acta Gymnica, Vol. 47, No. 3, 01.01.2017, p. 112-121.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Vagal activity and oxygen saturation response to hypoxia

T2 - Effects of aerobic fitness and rating of hypoxia tolerance

AU - Macoun, Tomáš

AU - Botek, Michal

AU - Krejčí, Jakub

AU - McKune, Andrew J.

PY - 2017/1/1

Y1 - 2017/1/1

N2 - Background: A reduction in the inspired oxygen fraction (FiO2) induces a decline in arterial oxygen saturation (SpO2) and changes of heart rate variability (HRV). It has been shown that SpO2 and HRV responses to similar levels of acute normobaric hypoxia are inter-individual variable. Variable response may be influenced by normoxia reached maximal oxygen uptake (VO2max) value. Objective: The primary aim was to assess HRV and the SpO2 response to hypoxia, and examine the association with normoxic VO2max. Methods: Supine HRV and SpO2 were monitored during normobaric hypoxia (FiO2 = 9.6%) for 10 minutes in 28 subjects, aged 23.7 ± 1.7 years. HRV was evaluated by using both spectral and time domain HRV analysis. Low frequency (LF, 0.05-0.15 Hz) and high frequency (HF, 0.15-0.50 Hz) power together with square root of the mean of the squares of the successive differences (rMSSD) were calculated and transformed by natural logarithm (Ln). Based on the SpO2 in hypoxia, subjects were divided into Resistant (RG, SpO2 ≥ 70.9%, n = 14) and Sensitive (SG, SpO2 < 70.9%, n = 14) groups. Perceived hypoxia tolerance was self-scored on a 4-level scale. Results: VO2max was higher in SG (62.4 ± 7.2 ml · kg-1 · min-1) compared with RG (55.5 ± 7.1 ml · kg-1 · min-1, p =.017, d = 0.97). A significant relationship (r = -.45, p =.017) between hypoxicnormoxic difference in SpO2 and normoxic VO2max level was found. Vagal activity (Ln rMSSD) was significantly decreased (SG: p <.001, d = 2.64; RG: p <.001, d = 1.22), while sympathetic activity (Ln LF/HF) was relatively increased (p <.001, d = -1.40) in only the SG during hypoxia. Conclusions: Results show that subjects with a higher aerobic capacity exhibited a greater decline in SpO2, accompanied by greater autonomic cardiac disturbances during hypoxia. The SpO2 reduction was associated with perceived hypoxia comfort/discomfort. The hypoxia discomfort state was accompanied by a greater withdrawal in cardiac vagal activity.

AB - Background: A reduction in the inspired oxygen fraction (FiO2) induces a decline in arterial oxygen saturation (SpO2) and changes of heart rate variability (HRV). It has been shown that SpO2 and HRV responses to similar levels of acute normobaric hypoxia are inter-individual variable. Variable response may be influenced by normoxia reached maximal oxygen uptake (VO2max) value. Objective: The primary aim was to assess HRV and the SpO2 response to hypoxia, and examine the association with normoxic VO2max. Methods: Supine HRV and SpO2 were monitored during normobaric hypoxia (FiO2 = 9.6%) for 10 minutes in 28 subjects, aged 23.7 ± 1.7 years. HRV was evaluated by using both spectral and time domain HRV analysis. Low frequency (LF, 0.05-0.15 Hz) and high frequency (HF, 0.15-0.50 Hz) power together with square root of the mean of the squares of the successive differences (rMSSD) were calculated and transformed by natural logarithm (Ln). Based on the SpO2 in hypoxia, subjects were divided into Resistant (RG, SpO2 ≥ 70.9%, n = 14) and Sensitive (SG, SpO2 < 70.9%, n = 14) groups. Perceived hypoxia tolerance was self-scored on a 4-level scale. Results: VO2max was higher in SG (62.4 ± 7.2 ml · kg-1 · min-1) compared with RG (55.5 ± 7.1 ml · kg-1 · min-1, p =.017, d = 0.97). A significant relationship (r = -.45, p =.017) between hypoxicnormoxic difference in SpO2 and normoxic VO2max level was found. Vagal activity (Ln rMSSD) was significantly decreased (SG: p <.001, d = 2.64; RG: p <.001, d = 1.22), while sympathetic activity (Ln LF/HF) was relatively increased (p <.001, d = -1.40) in only the SG during hypoxia. Conclusions: Results show that subjects with a higher aerobic capacity exhibited a greater decline in SpO2, accompanied by greater autonomic cardiac disturbances during hypoxia. The SpO2 reduction was associated with perceived hypoxia comfort/discomfort. The hypoxia discomfort state was accompanied by a greater withdrawal in cardiac vagal activity.

KW - Acute mountain sickness

KW - Haemoglobin desaturation

KW - Heart rate variability

KW - Maximal oxygen uptake

KW - Simulated altitude

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VL - 47

SP - 112

EP - 121

JO - Acta Universitatis Palackianae Olomucensis, Gymnica

JF - Acta Universitatis Palackianae Olomucensis, Gymnica

SN - 2336-4912

IS - 3

ER -