Chemoreceptor Responsiveness at Sea Level Does Not Predict the Pulmonary Pressure Response to High Altitude

Hoiland, Ryan L.; Foster, Glen E.; Donnelly, Joseph E.; Stembridge, Mike; Willie, Christopher K.; Smith, Kurt J.; Lewis, Nia C. S.; Lucas, Samuel J. E.; Cotter, Jim; Yeoman, David J.; Thomas, Kate N.; Day, Trevor A.; Tymko, Mike; Burgess, Keith R.; Ainslie, Philip N.

doi:10.1378/chest.14-1992

Cited by 9 publications

(8 citation statements)

References 53 publications

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“…Based on our previous exercise and high-altitude studies (e.g. [ 16 – 21 ]) adequate sample sizes for each of the outlined studies, accounting for potential subject dropout, were determined by related statistical power calculations whereby a power of 0.8 was assumed, and an alpha value of 0.05 was set (G*power). Depending on the variability of the primary outcome of each study (e.g., CBF, PASP, etc.…”

Section: Methodsmentioning

confidence: 99%

UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya

et al. 2018

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The University of British Columbia Nepal Expedition took place over several months in the fall of 2016 and was comprised of an international team of 37 researchers. This paper describes the objectives, study characteristics, organization and management of this expedition, and presents novel blood gas data during acclimatization in both lowlanders and Sherpa. An overview and framework for the forthcoming publications is provided. The expedition conducted 17 major studies with two principal goals—to identify physiological differences in: 1) acclimatization; and 2) responses to sustained high-altitude exposure between lowland natives and people of Tibetan descent. We performed observational cohort studies of human responses to progressive hypobaric hypoxia (during ascent), and to sustained exposure to 5050 m over 3 weeks comparing lowlander adults (n = 30) with Sherpa adults (n = 24). Sherpa were tested both with (n = 12) and without (n = 12) descent to Kathmandu. Data collected from lowlander children (n = 30) in Canada were compared with those collected from Sherpa children (n = 57; 3400–3900m). Studies were conducted in Canada (344m) and the following locations in Nepal: Kathmandu (1400m), Namche Bazaar (3440m), Kunde Hospital (3480m), Pheriche (4371m) and the Ev-K2-CNR Research Pyramid Laboratory (5050m). The core studies focused on the mechanisms of cerebral blood flow regulation, the role of iron in cardiopulmonary regulation, pulmonary pressures, intra-ocular pressures, cardiac function, neuromuscular fatigue and function, blood volume regulation, autonomic control, and micro and macro vascular function. A total of 335 study sessions were conducted over three weeks at 5050m. In addition to an overview of this expedition and arterial blood gas data from Sherpa, suggestions for scientists aiming to perform field-based altitude research are also presented. Together, these findings will contribute to our understanding of human acclimatization and adaptation to the stress of residence at high-altitude.

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Section: Methodsmentioning

confidence: 99%

UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya

et al. 2018

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“…Although the steady-state hypoxia test aims to target the peripheral chemoreceptors, quantification of the ventilatory responses may be confounded by the duration of these tests (e.g. 10-20 min; Steinback & Poulin, 2007;Hoiland et al 2015b). For example, variable changes in P aCO 2 during the steady-state poikilocapnic hypoxia test can dramatically modify the ventilatory response magnitude (Steinback & Poulin, 2007).…”

Section: Advantages and Utility Of The Transient Testsmentioning

confidence: 99%

Comparing and characterizing transient and steady‐state tests of the peripheral chemoreflex in humans

Pfoh

Tymko

Abrosimova

et al. 2016

Experimental Physiology

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“…A feature of our comparison of the ventilatory and the pulmonary vascular acclimatization to hypoxia is the finding that the two physiological processes show no correlation. Perhaps in keeping with this a recent study at high altitude found no correlation between the eucapnic hypoxic ventilatory response measured at sea level and the elevation in PASP measured at an altitude of 5050 m (Hoiland et al 2014). .…”

Section: Differences Between the Ventilatory And Pulmonary Vascular Amentioning

confidence: 55%

“…Perhaps in keeping with this a recent study at high altitude found no correlation between the eucapnic hypoxic ventilatory response measured at sea level and the elevation in PASP measured at an altitude of 5050 m (Hoiland et al . ).…”

Section: Differences Between the Ventilatory And Pulmonary Vascular Amentioning

confidence: 97%

Determinants of ventilation and pulmonary artery pressure during early acclimatization to hypoxia in humans

Fatemian

Herigstad

Croft

et al. 2015

The Journal of Physiology

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Key points Lung ventilation and pulmonary artery pressure rise progressively in response to 8 h of hypoxia, changes described as ‘acclimatization to hypoxia’. Acclimatization responses differ markedly between humans for unknown reasons.We explored whether the magnitudes of the ventilatory and vascular responses were related, and whether the degree of acclimatization could be predicted by acute measurements of ventilatory and vascular sensitivities.In 80 healthy human volunteers measurements of acclimatization were made before, during, and after a sustained exposure to 8 h of isocapnic hypoxia.No correlation was found between measures of ventilatory and pulmonary vascular acclimatization.The ventilatory chemoreflex sensitivities to acute hypoxia and hypercapnia all increased in proportion to their pre‐acclimatization values following 8 h of hypoxia. The peripheral (rapid) chemoreflex sensitivity to CO2, measured before sustained hypoxia against a background of hyperoxia, was a modest predictor of ventilatory acclimatization to hypoxia. This finding has relevance to predicting human acclimatization to the hypoxia of altitude. AbstractPulmonary ventilation and pulmonary arterial pressure both rise progressively during the first few hours of human acclimatization to hypoxia. These responses are highly variable between individuals, but the origin of this variability is unknown. Here, we sought to determine whether the variabilities between different measures of response to sustained hypoxia were related, which would suggest a common source of variability. Eighty volunteers individually underwent an 8‐h isocapnic exposure to hypoxia (end‐tidal P O2=55 Torr) in a purpose‐built chamber. Measurements of ventilation and pulmonary artery systolic pressure (PASP) assessed by Doppler echocardiography were made during the exposure. Before and after the exposure, measurements were made of the ventilatory sensitivities to acute isocapnic hypoxia (GnormalpO2) and hyperoxic hypercapnia, the latter divided into peripheral (G pC O2) and central (G cC O2) components. Substantial acclimatization was observed in both ventilation and PASP, the latter being 40% greater in women than men. No correlation was found between the magnitudes of pulmonary ventilatory and pulmonary vascular responses. For GnormalpO2, G pC O2 and G cC O2, but not the sensitivity of PASP to acute hypoxia, the magnitude of the increase during acclimatization was proportional to the pre‐acclimatization value. Additionally, the change in GnormalpO2 during acclimatization to hypoxia correlated well with most other measures of ventilatory acclimatization. Of the initial measurements prior to sustained hypoxia, only G pC O2 predicted the subsequent rise in ventilation and change in GnormalpO2 during acclimatization. We conclude that the magnitudes of the ventilatory and pulmonary vascular responses to sustained hypoxia are predominantly determined by different factors and that the initial G pC O2 is a modest predictor of ventilatory acclimatization.

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Chemoreceptor Responsiveness at Sea Level Does Not Predict the Pulmonary Pressure Response to High Altitude

Cited by 9 publications

References 53 publications

UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya

UBC-Nepal Expedition: An experimental overview of the 2016 University of British Columbia Scientific Expedition to Nepal Himalaya

Comparing and characterizing transient and steady‐state tests of the peripheral chemoreflex in humans

Determinants of ventilation and pulmonary artery pressure during early acclimatization to hypoxia in humans

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