Tissue deoxygenation kinetics induced by prolonged hypoxic exposure in healthy humans at rest

Rupp, Thomas; Leti, Thomas; Jubeau, Marc; Millet, Guillaume Y.; Bricout, Véronique-Aurélie; Lévy, Patrick; Wuyam, Bernard; Perrey, Stéphane; Vergès, Samuel

doi:10.1117/1.jbo.18.9.095002

Cited by 23 publications

(23 citation statements)

References 68 publications

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“…8,11,20,[22][23][24][25][26] The length of stay and type of rise to a simulated altitude could generate different cardiac autonomic modulation responses, as shown in the table 1. 12,27,28 Likewise, the different levels of oxygen used in the studies, ranging from 19% to 9.6% of FiO 2 10,21,23 also appear to induce different HRV responses.…”

Section: Intervening Factors Of Hypoxia In Hrvmentioning

confidence: 92%

“…24 After this, they suggest two possible routes, one relates to a possible baroreflex response that may counterbalance the initial disturbance, preventing very high levels of HR 31 or even, in the possibility of fall in SpO 2 below a certain threshold, cause a negligible change in ANS activity. 24 Although SpO 2 was not been stabilized during 10-min exposure, the study by Rupp et al 28 indicates SpO 2 stabilization only after 20-minute exposure to a level of 12% FiO 2 at 4000 m, i.e., less than that achieved by Krejci et al 24 One only study 21 separated the sample into two groups, RG = SpO 2 ≥ 72.2% and SG = SpO 2 ≤ 72.2%, in addition to controlling RF and using an extreme level of hypoxia of ~6200m. In this study of rapid exposure to NH, the RG group had a decrease in LnHF but with maintenance of Ln LF/HF.…”

Section: Exposure To Hypoxia and Its Effects On Hrvmentioning

confidence: 96%

“…Of the selected studies, five showed an increase in sympathovagal balance, estimated by the LF/HF ratio [10][11][12]26,28 after exposure to hypoxia. Studies by Rupp et al 28 , Basualto-Alarcon et al 11 and Guger et al 12 ,…”

Section: Exposure To Hypoxia and Its Effects On Hrvmentioning

confidence: 99%

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Effects of Hypoxia on Heart Rate Variability in Healthy Individuals: A Systematic Review

Oliveira¹,

Rohan²,

Gonçalves³

et al. 2017

International Journal of Cardiovascular Sciences

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Background: Hypoxia is a physiological condition that may affect the cardiac autonomic modulation, which can be assessed by spontaneous fluctuations in heart rate, know as heart rate variability (HRV). Studies have reported reductions or maintenance of HRV in hypoxic situation presenting controversial effects. There is a knowledge gap in relation to changes in HRV during hypoxia.Objective: The aim of this study was to systematically review the effects of hypoxia on HRV in unacclimatized healthy adults at rest. Methods:This systematic review was performed according to PRISMA guidelines. Search terms used in MEDLINE, SCOPUS, LILACS and EUROPE PMC database were: "heart rate variability" OR "cardiac autonomic modulation" OR "cardiac autonomic regulation" AND NOT intermittent NOT sleep (hypoxia OR altitude). Records were filtered by species, age group and language. Results: At the end of the screening and eligibility, 13 manuscripts remained for qualitative synthesis. Discussion:The studies used different experimental protocols involving difference in barometric pressure, oxygen level, time of exposure to hypoxia and control of respiratory rate. Possibly the influence of these factors and also the interindividual variation to hypoxia may justify different responses in HRV. Conclusion:Based on the investigated studies, hypoxia has been capable of generating a decrease in HRV, either by reduction or maintenance of vagal modulation, or by sympathetic predominance or even the combination of these responses in healthy adults unacclimatized to hypoxia. This effect appears to be dependent on altitude level and barometric pressure. (Int J Cardiovasc Sci. 2017;30(3):251-261)

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Section: Intervening Factors Of Hypoxia In Hrvmentioning

confidence: 92%

Section: Exposure To Hypoxia and Its Effects On Hrvmentioning

confidence: 96%

See 1 more Smart Citation

Effects of Hypoxia on Heart Rate Variability in Healthy Individuals: A Systematic Review

Oliveira¹,

Rohan²,

Gonçalves³

et al. 2017

International Journal of Cardiovascular Sciences

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“…This time point coincides with significant and near maximal reduction in cerebral oxygenation measured by near-infrared spectroscopy during a 4-hour hypoxic exposure (FiO 2 = 0.12) at rest. 16 Shortterm changes in cerebral volume are commonly caused by changes in tissue water content or perfusion. The absence of significant change in ADC after 30 minutes of exposure suggests that edema is not responsible for this early increase in whitematter volume.…”

Section: Correlationsmentioning

confidence: 99%

“…7 We also assessed potential early MRI changes after 30 minutes of passive hypoxic exposure, i.e., the hypoxic exposure duration eliciting maximal cerebral deoxygenation (assessed in a recent report from our group by near-infrared spectroscopy). 16 We hypothesized that (1) hypoxia would induce signs of cerebral edema as early as after 30 minutes and this would be exacerbated after 10 hours of exposure and (2) hypoxia associated with exercise would induce similar changes in brain volumes and ADC as hypoxia at rest with matched arterial oxygenation levels, i.e., demonstrating the primary role of hypoxemia regarding cerebral changes.…”

Section: Introductionmentioning

confidence: 99%

Cerebral Volumetric Changes Induced by Prolonged Hypoxic Exposure and Whole-Body Exercise

Rupp

Jubeau

Lamalle

et al. 2014

J Cereb Blood Flow Metab

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The present study assessed the isolated and synergetic effects of hypoxic exposure and prolonged exercise on cerebral volume and subedema and symptoms of acute mountain sickness (AMS). Twelve healthy males performed three semirandomized blinded 11-hour sessions with (1) an inspiratory oxygen fraction (FiO 2 ) of 12% and 4-hour cycling, (2) FiO 2 = 21% and 4-hour cycling, and (3) FiO 2 = 8.5% to 12% at rest (matching arterial oxygen saturation measured during the first hypoxic session). Volumetric, apparent diffusion coefficient (ADC), and arterial spin labelling 3T magnetic resonance imaging sequences were performed after 30 minutes and 10 hours in each session. Thirty minutes of hypoxia at rest induced a significant increase in white-matter volume (+0.8 ± 1.0% compared with normoxia) that was exacerbated after 10 hours of hypoxia at rest (+1.5 ± 1.1%) or with cycling (+1.6 ± 1.1%). Total brain parenchyma volume increased significantly after 10 hours of hypoxia with cycling only (+1.3 ± 1.1%). Apparent diffusion coefficient was significantly reduced after 10 hours of hypoxia at rest or with cycling. No significant change in cerebral blood flow was observed. These results demonstrate changes in white-matter volume as early as after 30 minutes of hypoxia that worsen after 10 hours, probably due to cytotoxic edema. Exercise accentuates the effect of hypoxia by increasing total brain volume. These changes do not however correlate with AMS symptoms.

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HIF-1-driven skeletal muscle adaptations to chronic hypoxia: molecular insights into muscle physiology

Favier

Britto

Freyssenet

et al. 2015

Cell. Mol. Life Sci.

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Skeletal muscle is a metabolically active tissue and the major body protein reservoir. Drop in ambient oxygen pressure likely results in a decrease in muscle cells oxygenation, reactive oxygen species (ROS) overproduction and stabilization of the oxygen-sensitive hypoxia-inducible factor (HIF)-1α. However, skeletal muscle seems to be quite resistant to hypoxia compared to other organs, probably because it is accustomed to hypoxic episodes during physical exercise. Few studies have observed HIF-1α accumulation in skeletal muscle during ambient hypoxia probably because of its transient stabilization. Nevertheless, skeletal muscle presents adaptations to hypoxia that fit with HIF-1 activation, although the exact contribution of HIF-2, I kappa B kinase and activating transcription factors, all potentially activated by hypoxia, needs to be determined. Metabolic alterations result in the inhibition of fatty acid oxidation, while activation of anaerobic glycolysis is less evident. Hypoxia causes mitochondrial remodeling and enhanced mitophagy that ultimately lead to a decrease in ROS production, and this acclimatization in turn contributes to HIF-1α destabilization. Likewise, hypoxia has structural consequences with muscle fiber atrophy due to mTOR-dependent inhibition of protein synthesis and transient activation of proteolysis. The decrease in muscle fiber area improves oxygen diffusion into muscle cells, while inhibition of protein synthesis, an ATP-consuming process, and reduction in muscle mass decreases energy demand. Amino acids released from muscle cells may also have protective and metabolic effects. Collectively, these results demonstrate that skeletal muscle copes with the energetic challenge imposed by O2 rarefaction via metabolic optimization.

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Tissue deoxygenation kinetics induced by prolonged hypoxic exposure in healthy humans at rest

Cited by 23 publications

References 68 publications

Effects of Hypoxia on Heart Rate Variability in Healthy Individuals: A Systematic Review

Effects of Hypoxia on Heart Rate Variability in Healthy Individuals: A Systematic Review

Cerebral Volumetric Changes Induced by Prolonged Hypoxic Exposure and Whole-Body Exercise

HIF-1-driven skeletal muscle adaptations to chronic hypoxia: molecular insights into muscle physiology

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