Abstract
Altitude illness remains a major cause of mortality. Reduced chemosensitivity, irregular breathing leading to central apnoeas/hypopnoeas, and exaggerated pulmonary vasoconstriction may compromise oxygenation. All factors could enhance susceptibility to acute mountain sickness (AMS).
We compared 12 AMS-susceptible individuals with recurrent and severe symptoms (AMS+) with 12 “AMS-nonsusceptible” subjects (AMS-), assessing sleep-breathing disorders in simulated altitude as well as chemoresponsive and pulmonary vasoconstrictive responses to hypoxia.
During exposure to simulated altitude, mean blood oxygen saturation during sleep was lower in AMS+ subjects (81.6±2.6 versus 86.0±2.4%, p<0.01), associated with a lower central apnoea/hypopnoea index (18.2±18.1 versus 33.4±24.8 events·h−1 in AMS+ and AMS- subjects, respectively; p=0.038). A lower hypoxic (isocapnic) chemoresponsiveness was observed in AMS+ subjects (0.40±0.49 versus 0.97±0.46 L·min−1·%; p<0.001). This represented the only significant and independent predictive factor for altitude intolerance, despite a higher increase in pulmonary artery systolic pressure in response to hypoxia, a lower lung diffusing capacity and a higher endothelin-1 level at baseline in AMS+ subjects (p<0.05). AMS+ subjects were more hypoxaemic whilst exhibiting fewer respiratory events during sleep owing to lower hypoxic (isocapnic) chemoresponsiveness.
In conclusion, the reduction in peripheral hypoxic chemosensitivity appears to be a major causative factor for altitude intolerance.
Footnotes
This article has supplementary material available from www.erj.ersjournals.com
Support Statement
Funding was provided by the PHRC Inter-Régional 2007, Conseil Scientifique AGIRadom, Région Rhône-Alpes (Projet CIBLE 2010). The authors are grateful to the DRCI CHU de Grenoble (PHRC Régional 2007 “ALT” awarded to B. Wuyam), Conseil scientifique AGIRadom (awarded to B. Wuyam and H. Nespoulet), and the ANR “Tech-scan” (awarded to J-L. Pépin) for financial support.
Statement of Interest
None declared.
- Received April 29, 2011.
- Accepted January 20, 2012.
- ©ERS 2012