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Lung diffusing capacity and exercise in subjects with previous high altitude pulmonary oedema
J M Steinacker1, P Tobias, E Menold
1Abt. Sport- und Leistungsmedizin, Medizinische Klinik und Poliklinik, Universität Ulm, Germany.
The European Respiratory Journal
|May 22, 1998
Summary
Individuals susceptible to high-altitude pulmonary edema (HAPE) exhibit impaired pulmonary diffusing capacity and cardiac output during exercise. HAPE-resistant individuals show greater lung volumes and vascular responsiveness, suggesting a protective physiological difference.
Area of Science:
- Physiology
- Altitude Medicine
- Pulmonary Medicine
Background:
- High-altitude pulmonary edema (HAPE) is associated with increased pulmonary artery pressure and ventilation-perfusion (V'A/Q') inhomogeneity during hypoxia and exercise.
- Understanding the physiological differences in individuals susceptible or resistant to HAPE is crucial for prevention and management.
Purpose of the Study:
- To investigate differences in pulmonary diffusing capacity for carbon monoxide (DL,CO) and cardiac output (Q') during exercise between HAPE-susceptible and HAPE-resistant individuals.
- To determine if these differences indicate a more restricted pulmonary vascular bed in HAPE-susceptible subjects.
Main Methods:
- Noninvasive methods including CO and acetylene rebreathing techniques were used.
- Eight HAPE-susceptible and five HAPE-resistant subjects underwent pulmonary function testing during exercise at 30% and 50% of maximal oxygen consumption (V'O2) under normoxic and hypoxic conditions (inspiratory oxygen fraction of 0.14 and 0.21).
Main Results:
- HAPE-resistant subjects had significantly larger functional residual capacity, vital capacity, and total lung capacity.
- DL,CO was lower in HAPE-susceptible subjects during hypoxia and exercise, with a blunted increase (32% vs. 49%) under combined hypoxic exercise.
- HAPE-susceptible subjects demonstrated smaller increases in stroke volume, cardiac output (Q'), and ventilation during exercise.
Conclusions:
- HAPE-susceptible individuals exhibit a more restricted pulmonary vascular bed during exercise compared to HAPE-resistant individuals.
- Findings suggest lower pulmonary vasoconstriction, greater vascular capacitance, and enhanced ventilatory responsiveness in HAPE-resistant subjects.
- Larger lung volumes in HAPE-resistant individuals may indicate a constitutional predisposition to HAPE resistance.