Operation Everest II

Rb, Schoene; Roach, Robert C.; Ph, Hackett; Sutton,; Cymerman, Allen; Cs, Houston

doi:10.1249/00005768-199012000-00012

Cited by 55 publications

(12 citation statements)

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“…Similar to the HVR, an increase in HCVR also appears during chronic exposure to hypoxia (Forster et al 1971;Sato et al 1992Sato et al , 1994Schoene et al 1990). The slope of HCVR, i.e., D _ V I /DPETCO 2 , is considered to be a response mediated primarily through the central chemoreceptors (Read and Leigh 1967), although the ventilatory response to hyperoxic hypercapnia includes a contribution from peripheral chemoreceptors.…”

Section: Discussionmentioning

confidence: 94%

“…As far as we know, this is the first report to evaluate the effect of the duration, per day, of intermittent hypoxia on HVR and HCVR in humans. It is well known that acute HVR is increased during chronic exposure to hypoxia or sojourns at high altitude (Forster et al 1971;Sato et al 1992Sato et al , 1994Schoene et al 1990;White et al 1987). It has showed that carotid sinus nerve activity is enhanced during hypoxic exposure in animal studies (Vizek et al 1987;Nielsen et al 1988).…”

Section: Discussionmentioning

confidence: 99%

“…It has been revealed that chronic exposure to hypoxia or sojourns at high altitude leads to increases in acute hypoxic and hypercapnic ventilatory responses (HVR and HCVR), as indexes of the ventilatory chemosensitivities to hypoxia and hypercapnia (Forster et al 1971;Sato et al 1992Sato et al , 1994Schoene et al 1990;White et al 1987). In addition to chronic hypoxic exposure, recent studies have investigated the influence of short-term intermittent hypoxia, resembling the pattern of rapid ascents to and descents from high altitude, on ventilatory chemosensitivity in humans.…”

Section: Introductionmentioning

confidence: 99%

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Effect of two durations of short-term intermittent hypoxia on ventilatory chemosensitivity in humans

et al. 2009

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The purpose of this study was to clarify the influence of duration of intermittent hypoxia per day on ventilatory chemosensitivity. Subjects were assigned to three different groups according to the duration of exposure to intermittent hypoxia (12.3 +/- 0.2% O(2)): a first group (H-1, n = 6) was exposed to hypoxia for 1 h per day, the second group (H-2, n = 6) was exposed for 3 h per day, and the third (C, n = 7) was used as control. Hypoxic and hypercapnic ventilatory responses (HVR and HCVR) were determined before and after 1 week of intermittent hypoxia. HVR was increased significantly (P < 0.05) after intermittent hypoxia in both the H-1 and H-2 groups. However, there was no significant difference in magnitude of increased HVR between H-1 and H-2 groups. HCVR did not show any changes in all groups after intermittent hypoxia. These results suggest that 1 h of daily exposure is as equally effective as 3 h of daily exposure to severe hypoxia for a short period for enhancing ventilatory chemosensitivity to hypoxia.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of two durations of short-term intermittent hypoxia on ventilatory chemosensitivity in humans

et al. 2009

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“…5 -8 Thus, our IH study showed that low hypoxic level and short repeated exposures at rest can induce physiological changes usually observed during the acclimatization process to continuous hypoxia (CH). [9][10][11] The purpose of the present study was to further investigate the effect of IH by comparing the time course and the magnitude of the ventilatory and hematological changes during IH and continuous exposure to the same level of hypoxia. Unfortunately, it was impossible to study all 9 subjects from the original IH protocol, but we did recruit 4 of the subjects to the new protocol.…”

Section: Introductionmentioning

confidence: 99%

Intermittent vs continuous hypoxia: effects on ventilation and erythropoiesis in humans

Garcia

Hopkins

Powell

2000

Wilderness & Environmental Medicine

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“…In response to chronic HA exposure, the sensitivity of the peripheral chemoreflex is augmented driving (a) increases in the magnitude of the hypoxic ventilatory response (HVR; Howard & Robbins, 1995; Sato et al, 1992; Teppema & Dahan, 2010; White et al, 1987), and subsequently (b) increases steady‐state breathing while hypoxic (Duffin & Mahamed, 2003; Eger et al, 1968; Michel & Milledge, 1963). The central chemoreflex is also augmented during chronic exposure to hypoxia (Fan et al, 2010), in part due to the renally mediated elimination of bicarbonate ions (HCO 3 − ) and associated reduced buffering capacity in the central compartment, as the kidneys compensate for the sustained respiratory alkalosis (Krapf et al, 1991; Mathew et al, 1983; Pitts et al, 1948; Schoene et al, 1990; Severinghaus et al, 1963). This renal elimination of HCO 3 − in the context of chronic hypobaric hypoxia increases the relative stimulation of central chemoreceptors via [H + ] for a given CO 2 challenge (e.g., Ainslie et al, 2013; Fan et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Steady‐state chemoreflex drive captures ventilatory acclimatization during incremental ascent to high altitude: Effect of acetazolamide

Cates

Bruce

Marullo

et al. 2022

Physiological Reports

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Ventilatory acclimatization (VA) is important to maintain adequate oxygenation with ascent to high altitude (HA). Transient hypoxic ventilatory response tests lack feasibility and fail to capture the integrated steady‐state responses to chronic hypoxic exposure in HA fieldwork. We recently characterized a novel index of steady‐state respiratory chemoreflex drive (SSCD), accounting for integrated contributions from central and peripheral respiratory chemoreceptors during steady‐state breathing at prevailing chemostimuli. Acetazolamide is often utilized during ascent for prevention or treatment of altitude‐related illnesses, eliciting metabolic acidosis and stimulating respiratory chemoreceptors. To determine if SSCD reflects VA during ascent to HA, we characterized SSCD in 25 lowlanders during incremental ascent to 4240 m over 7 days. We subsequently compared two separate subgroups: no acetazolamide (NAz; n = 14) and those taking an oral prophylactic dose of acetazolamide (Az; 125 mg BID; n = 11). At 1130/1400 m (day zero) and 4240 m (day seven), steady‐state measurements of resting ventilation (V̇ I ; L/min), pressure of end‐tidal (P ET )CO 2 (Torr), and peripheral oxygen saturation (SpO 2 ; %) were measured. A stimulus index (SI; P ET CO 2 /SpO 2 ) was calculated, and SSCD was calculated by indexing V̇ I against SI. We found that (a) both V̇ I and SSCD increased with ascent to 4240 m (day seven; V̇ I : +39%, p < 0.0001, Hedges' g = 1.52; SSCD: +56.%, p < 0.0001, Hedges' g = 1.65), (b) and these responses were larger in the Az versus NAz subgroup (V̇ I : p = 0.02, Hedges' g = 1.04; SSCD: p = 0.02, Hedges' g = 1.05). The SSCD metric may have utility in assessing VA during prolonged stays at altitude, providing a feasible alternative to transient chemoreflex tests.

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Operation Everest II

Cited by 55 publications

References 0 publications

Effect of two durations of short-term intermittent hypoxia on ventilatory chemosensitivity in humans

Effect of two durations of short-term intermittent hypoxia on ventilatory chemosensitivity in humans

Intermittent vs continuous hypoxia: effects on ventilation and erythropoiesis in humans

Steady‐state chemoreflex drive captures ventilatory acclimatization during incremental ascent to high altitude: Effect of acetazolamide

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