Specific effect of hypobaria on cerebrovascular hypercapnic responses in hypoxia

Aebi, Mathias R.; Bourdillon, Nicolas; Kunz, Andres; Bron, Denis; Millet, Grégoire P.

doi:10.14814/phy2.14372

Cited by 12 publications

(16 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is known that the cardiac autonomic nerve activity is influenced by ventilation ( Brown et al, 1993 ). In a parallel article from our laboratory, minute ventilation and breathing frequency significantly increased in HH5500, but not NH, when compared to NN at rest ( Aebi et al, 2020 ). Moreover, tidal volume tended to be higher in HH5500 than NN, while it remained unchanged in NH ( Aebi et al, 2020 ).…”

Section: Resultsmentioning

confidence: 95%

“…In a parallel article from our laboratory, minute ventilation and breathing frequency significantly increased in HH5500, but not NH, when compared to NN at rest (Aebi et al, 2020). Moreover, tidal volume tended to be higher in HH5500 than NN, while it remained unchanged in NH (Aebi et al, 2020). Gas exchanges data were FIGURE 1 | The root mean square of the successive differences (RMSSD) for each subject.…”

Section: Influence Of Ventilation On Heart Rate Variabilitymentioning

confidence: 95%

“…Each tested condition consisted 5 min of condition acclimatization followed by 6 min seated at rest. Then, participants also performed a concentration test [arithmetic tasks including working memory, KLT-R test ( Düker and Lienert, 2001 )] and hypercapnic breathing protocol to assess cerebrovascular reactivity to CO 2 ( Aebi et al, 2020 ). Each period lasted for 30 min, interspaced by a 30 min rest period in NN, for total session duration of 5 h.…”

Section: Methodsmentioning

confidence: 99%

“…Contradictory, HH is suggested as a more severe environmental condition than NH ( Millet et al, 2012 ). Several differences between NH and HH were reported, such as minute ventilation ( Savourey et al, 2003 ), oxydative stress ( Faiss et al, 2013 ), sleep disturbance ( Saugy et al, 2016 ), and cerebrovascular function ( Aebi et al, 2020 ). Therefore, NH and HH are not interchangeable ( Conkin, 2016 ) but the clinical significance of the difference remains highly debated ( Millet and Debevec, 2020 ; Richalet, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

et al. 2020

Self Cite

View full text Add to dashboard Cite

Introduction: The present study evaluated the putative effect of hypobaria on resting HRV in normoxia and hypoxia. Methods: Fifteen young pilot trainees were exposed to five different conditions in a randomized order: normobaric normoxia (NN, P B = 726 ± 5 mmHg, F I O 2 = 20.9%), hypobaric normoxia (HN, P B = 380 ± 6 mmHg, F I O 2 ∼ =40%), normobaric hypoxia (NH, P B = 725 ± 4 mmHg, F I O 2 ∼ =11%); and hypobaric hypoxia (HH at 3000 and 5500 m, HH3000 and HH5500, P B = 525 ± 6 and 380 ± 8 mmHg, respectively, F I O 2 = 20.9%). HRV and pulse arterial oxygen saturation (SpO 2) were measured at rest seated during a 6 min period in each condition. HRV parameters were analyzed (Kubios HVR Standard, V 3.0) for time (RMSSD) and frequency (LF, HF, LF/HF ratio, and total power). Gas exchanges were collected at rest for 10 min following HRV recording. Results: SpO 2 decreased in HH3000 (95 ± 3) and HH5500 (81 ± 5), when compared to NN (99 ± 0). SpO 2 was higher in NH (86 ± 4) than HH5500 but similar between HN (98 ± 2) and NN. Participants showed lower RMSSD and total power values in NH and HH5500 when compared to NN. In hypoxia, LF/HF ratio was greater in HH5500 than NH, whereas in normoxia, LF/HF ratio was lower in HN than NN. Minute ventilation was higher in HH5500 than in all other conditions. Discussion: The present study reports a slight hypobaric effect either in normoxia or in hypoxia on some HRV parameters. In hypoxia, with a more prominent sympathetic activation, the hypobaric effect is likely due to the greater ventilation stimulus and larger desaturation. In normoxia, the HRV differences may come from the hyperoxic breathing and slight breathing pattern change due to hypobaria in HN.

show abstract

Section: Resultsmentioning

confidence: 95%

Section: Influence Of Ventilation On Heart Rate Variabilitymentioning

confidence: 95%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Hypobaria also decreases air flow and work of breathing (Loeppky et al, 1997) and, due to greater physiological deadspace, increases the end-tidal PCO 2 /PaCO 2 gradient, thus further attenuating the ventilatory response (Savourey et al, 2003). Hypobaria may also increase pulmonary vasoconstriction (Petrassi et al, 2012;Conkin, 2016) and, in contrast to the aforementioned findings, reduce CBF (Aebi et al, 2020a). Therefore, for each EAA, only PiO 2 is equivalent between HH and NH; whereas, other factors contributing to the AGE may differ, such as gas flow distribution, diffusivity of gases and nitrogen kinetics, and the magnitude of hyperventilation-induced hypocapnia.…”

Section: Simulating Hypoxic Environmentsmentioning

confidence: 96%

Hypoxic Hypoxia and Brain Function in Military Aviation: Basic Physiology and Applied Perspectives

Shaw

Cabre²

2021

Front. Physiol.

View full text Add to dashboard Cite

Acute hypobaric hypoxia (HH) is a major physiological threat during high-altitude flight and operations. In military aviation, although hypoxia-related fatalities are rare, incidences are common and are likely underreported. Hypoxia is a reduction in oxygen availability, which can impair brain function and performance of operational and safety-critical tasks. HH occurs at high altitude, due to the reduction in atmospheric oxygen pressure. This physiological state is also partially simulated in normobaric environments for training and research, by reducing the fraction of inspired oxygen to achieve comparable tissue oxygen saturation [normobaric hypoxia (NH)]. Hypoxia can occur in susceptible individuals below 10,000 ft (3,048 m) in unpressurised aircrafts and at higher altitudes in pressurised environments when life support systems malfunction or due to improper equipment use. Between 10,000 ft and 15,000 ft (4,572 m), brain function is mildly impaired and hypoxic symptoms are common, although both are often difficult to accurately quantify, which may partly be due to the effects of hypocapnia. Above 15,000 ft, brain function exponentially deteriorates with increasing altitude until loss of consciousness. The period of effective and safe performance of operational tasks following exposure to hypoxia is termed the time-of-useful-consciousness (TUC). Recovery of brain function following hypoxia may also lag beyond arterial reoxygenation and could be exacerbated by repeated hypoxic exposures or hyperoxic recovery. This review provides an overview of the basic physiology and implications of hypoxia for military aviation and discusses the utility of hypoxia recognition training.

show abstract

Cardio-respiratory, oxidative stress and acute mountain sickness responses to normobaric and hypobaric hypoxia in prematurely born adults

et al. 2020

Self Cite

View full text Add to dashboard Cite

Purpose We compared the effects of hypobaric and normobaric hypoxia on select cardio-respiratory responses, oxidative stress and acute mountain sickness (AMS) severity in prematurely born individuals, known to exhibit blunted hypoxic ventilatory response. Methods Sixteen prematurely born but otherwise healthy males underwent two 8-h hypoxic exposures under: (1) hypobaric hypoxic [HH; terrestrial altitude 3840 m; P i O 2 :90.2 (0.5) mmHg; BP: 478 (2) mmHg] and (2) normobaric hypoxic [NH; P i O 2 :90.6 (0.9) mmHg; F i O 2 :0.142 (0.001)] condition. Resting values of capillary oxyhemoglobin saturation (SpO 2 ), heart rate (HR) and blood pressure were measured before and every 2 h during the exposures. Ventilatory responses and middle cerebral artery blood flow velocity (MCAv) were assessed at rest and during submaximal cycling before and at 4 and 8 h. Plasmatic levels of selected oxidative stress and antioxidant markers and AMS symptoms were also determined at these time points. Results HH resulted in significantly lower resting (P = 0.010) and exercise (P = 0.004) SpO 2 as compared to NH with no significant differences in the ventilatory parameters, HR or blood pressure. No significant differences between conditions were found in resting or exercising MCAv and measured oxidative stress markers. Significantly lower values of ferric-reducing antioxidant power (P = 0.037) were observed during HH as opposed to NH. AMS severity was higher at 8 h compared to baseline (P = 0.002) with no significant differences between conditions. Conclusion These data suggest that, in prematurely born adults, 8-h exposure to hypobaric, as opposed to normobaric hypoxia, provokes greater reductions in systemic oxygenation and antioxidant capacity. Further studies investigating prolonged hypobaric exposures in this population are warranted. Registration NCT02780908 (ClinicalTrials.gov).

show abstract

Specific effect of hypobaria on cerebrovascular hypercapnic responses in hypoxia

Cited by 12 publications

References 67 publications

Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

Minimal Influence of Hypobaria on Heart Rate Variability in Hypoxia and Normoxia

Hypoxic Hypoxia and Brain Function in Military Aviation: Basic Physiology and Applied Perspectives

Cardio-respiratory, oxidative stress and acute mountain sickness responses to normobaric and hypobaric hypoxia in prematurely born adults

Contact Info

Product

Resources

About