Ventilatory Acclimatization to Moderate Hypoxemia in Man

Dempsey, Jerome A.; Forster, H. V.; doPico, Guillermo A.

doi:10.1172/jci107646

Cited by 66 publications

(52 citation statements)

References 37 publications

(28 reference statements)

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“…29 Therefore, with acute hypoxia where brain tissue pH is increased, 30 a reduced hypercapnic CVR may serve to limit brain tissue pH to rise even further. This could be promoted by diminishing the washout of hydrogen ions and facilitating the hyperventilatory response to altitude exposure by an increased ventilatory drive.…”

Section: Discussionmentioning

confidence: 99%

Cerebrovascular Reactivity is Increased with Acclimatization to 3,454 M Altitude

Flück

Siebenmann

Keiser

et al. 2015

J Cereb Blood Flow Metab

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Controversy exists regarding the effect of high-altitude exposure on cerebrovascular CO 2 reactivity (CVR). Confounding factors in previous studies include the use of different experimental approaches, ascent profiles, duration and severity of exposure and plausibly environmental factors associated with altitude exposure. One aim of the present study was to determine CVR throughout acclimatization to high altitude when controlling for these. Middle cerebral artery mean velocity (MCAv mean ) CVR was assessed during hyperventilation (hypocapnia) and CO 2 administration (hypercapnia) with background normoxia (sea level (SL)) and hypoxia (3,454 m) in nine healthy volunteers (26 ± 4 years (mean ± s.d.)) at SL, and after 30 minutes (HA0), 3 (HA3) and 22 (HA22) days of high-altitude (3,454 m) exposure. At altitude, ventilation was increased whereas MCAv mean was not altered. Hypercapnic CVR was decreased at HA0 (1.16% ± 0.16%/mm Hg, mean ± s.e.m.), whereas both hyper-and hypocapnic CVR were increased at HA3 (3.13% ± 0.18% and 2.96% ± 0.10%/mm Hg) and HA22 (3.32% ± 0.12% and 3.24% ± 0.14%/mm Hg) compared with SL (1.98% ± 0.22% and 2.38% ± 0.10%/mm Hg; Po0.01) regardless of background oxygenation. Cerebrovascular conductance (MCAv mean /mean arterial pressure) CVR was determined to account for blood pressure changes and revealed an attenuated response. Collectively our results show that hypocapnic and hypercapnic CVR are both elevated with acclimatization to high altitude.

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Section: Discussionmentioning

confidence: 99%

Cerebrovascular Reactivity is Increased with Acclimatization to 3,454 M Altitude

Flück

Siebenmann

Keiser

et al. 2015

J Cereb Blood Flow Metab

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“…An arterial blood specimen was drawn over 1 min and analyzed at 37°C for pH, Paco2 and Pao2 with a Radiometer blood gas analyzer (Radiometer Co., Copenhagen, Denmark). Calibration of Pao2 and Paco2 electrodes were frequently validated using tonometered blood (17). At the same time, mixed expired gas was obtained and analyzed for C02, 02, and N2 with a gas chromatograph (QuinTron Instrument Co., Inc., Milwaukee, Wis.).…”

Section: Introductionmentioning

confidence: 99%

“…The techniques for anaerobic sampling and acid-base analyses of lumbar spinal fluid have been described previously (17).…”

Section: Introductionmentioning

confidence: 99%

“…Carbon dioxide retention in patients with high mechanical loads occurred concomitantly with a higher than normal inspiratory effort (mouth occlusion pressure) and normal minute ventilation to carbon dioxide production ratio (VIE/Vco2); but with shortened inspiratory time (1.3±0.1 vs. 1.8±3 s), increased breathing frequency (17±1 vs. 14±1 breaths/ min), low tidal volume (0.57±0.03 vs. 0.88±0.04 L), and high dead space to tidal volume ratio (0.63±0.02 vs. 0.39±0.07). Using a randomized application of treatment and placebo conditions, it was shown that 4 wk ofmedroxyprogesterone acetate caused significant reductions in Paco2 (from 51 + 1 to 42±1 mm Hg) in 10 of 17 patients. This "correction" of Paco2 in these patients was associated with increases in mouth occlusion pressure (14%), tidal volume (11%), and alveolar ventilation (15%) compared to placebo, although inspiratory time remained shortened.…”

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confidence: 99%

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Determinants of Chronic Carbon Dioxide Retention and Its Correction in Humans

Skatrud¹,

Dempsey²,

Bhansali³

et al. 1980

J. Clin. Invest.

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“…Our owin data obtained during acclimiatizationi points to a coimipletely different conclusion. NVe found that an increasing ventilation with time at high altitudes was not positively correlated with accoinpanying changes in CSF or plasma acidbase status or Po2 (4)(5)(6)(7)(8).…”

Section: Introductionmentioning

confidence: 89%

Role of Cerebrospinal Fluid [H+] in Ventilatory Deacclimatization from Chronic Hypoxia

Dempsey¹,

Forster²,

Bisgard³

et al. 1979

J. Clin. Invest.

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A B S T R A C T Once ventilatory acclinmatizationi beginsin sea level residents sojourning at high altitude, abrupt restoration of normal oxygen tensions will not restore ventilation to normal. We have investigated the role of cerebrospinal fluid (CSF) [He] in this sustained hyperventilation by measurinig CSF acid-base status in seven imien (lumbar) and five ponies (cisterinal) in normoxia, first at sea level anid then periodically over 13-24 h of"deacclimatization" after 3-5 d in hypoxia (PB = 440 mm Hg). After 1 h deaccliimcatization, hyperventilation continued at a level only slightly less than that obtained in chronic hypoxia (+ 1-2 mm Hg PA,O2), whereas CSF pH was either e(lual (in man) or alkaline (in pony, +0.02, P < 0.01) to sea level values. Between 1 and 12-13 h deacclimatization in all humans and ponies VA fell progressively (PA(,0( increased 4-7 mm Hg) and CSF pH became increasingly more acid (-0.02 to -0.05, P < 0.01). Between 12 acnd 24 h of normoxic deacclimatization in ponies, PAco, rose further toward norinal, coincideint with an increasing acidity in CSF (-0.02 pH). Similar negative correlations were found between changes in arterial pH and VA throughout normoxic deaccliimiatization. We conclude that [H+] in the lumbar or cisternal CSF is not the mediator of the continued hyperventilation and its gradual dissipation with time during normoxic deacclimatization from chronic hypoxia. These negative relationships of VA to CSF [H+] in normoxia are analogous to those previously shown during acclimatization to hypoxia.

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Ventilatory Acclimatization to Moderate Hypoxemia in Man

Cited by 66 publications

References 37 publications

Cerebrovascular Reactivity is Increased with Acclimatization to 3,454 M Altitude

Cerebrovascular Reactivity is Increased with Acclimatization to 3,454 M Altitude

Determinants of Chronic Carbon Dioxide Retention and Its Correction in Humans

Role of Cerebrospinal Fluid [H+] in Ventilatory Deacclimatization from Chronic Hypoxia

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