Abstract | BACKGROUND: The hypoxic ventilatory response (HVR) at sea level (SL) is moderately predictive of the change in pulmonary artery systolic pressure ( PASP) to acute normobaric hypoxia. However, because of progressive changes in the chemoreflex control of breathing and acid-base balance at high altitude (HA), HVR at SL may not predict PASP at HA. We hypothesized that resting oxygen saturation as measured by pulse oximetry (Spo₂) at HA would correlate better than HVR at SL with PASP at HA. METHODS: In 20 participants at SL, we measured normobaric, isocapnic HVR (L/min · -%Spo₂⁻¹) and resting PASP using echocardiography. Both resting Spo₂ and PASP measures were repeated on day 2 (n = 10), days 4 to 8 (n = 12), and 2 to 3 weeks (n = 8) after arrival at 5,050 m. These data were also collected at 5,050 m in life-long HA residents (ie, Sherpa [n = 21]). RESULTS: Compared with SL, Spo₂ decreased from 98.6% to 80.5% (P < .001), whereas PASP increased from 21.7 to 34.0 mm Hg (P < .001) after 2 to 3 weeks at 5,050 m. Isocapnic HVR at SL was not related to Spo₂ or PASP at any time point at 5,050 m (all P > .05). Sherpa had lower PASP (P < .01) than lowlanders on days 4 to 8 despite similar Spo₂. Upon correction for hematocrit, Sherpa PASP was not different from lowlanders at SL but was lower than lowlanders at all HA time points. At 5,050 m, although Spo₂ was not related to PASP in lowlanders at any point (all R² ≤ 0.05, P > .50), there was a weak relationship in the Sherpa (R² = 0.16, P = .07). CONCLUSIONS: We conclude that neither HVR at SL nor resting Spo₂ at HA correlates with elevations in PASP at HA.
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Authors | Ryan L Hoiland, Glen E Foster, Joseph Donnelly, Mike Stembridge, Chris K Willie, Kurt J Smith, Nia C Lewis, Samuel J E Lucas, Jim D Cotter, David J Yeoman, Kate N Thomas, Trevor A Day, Mike M Tymko, Keith R Burgess, Philip N Ainslie |
Journal | Chest
(Chest)
Vol. 148
Issue 1
Pg. 219-225
(Jul 2015)
ISSN: 1931-3543 [Electronic] United States |
PMID | 25501858
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
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Topics |
- Acclimatization
(physiology)
- Adult
- Altitude
- Arterial Pressure
(physiology)
- Baroreflex
(physiology)
- Chemoreceptor Cells
(physiology)
- Female
- Humans
- Hypercapnia
(etiology, physiopathology)
- Hypoxia
(etiology, physiopathology)
- Male
- Oximetry
- Oxygen
(blood)
- Pulmonary Artery
(physiopathology)
- Vascular Resistance
(physiology)
- Young Adult
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