Pulmonary capillary reserve and exercise capacity at high altitude in healthy humans

• Published in: European journal of applied physiology 2016-02, Vol.116 (2), p.427-437
• Main Authors: Taylor, Bryan J., Coffman, Kirsten E., Summerfield, Douglas T., Issa, Amine N., Kasak, Alex J., Johnson, Bruce D.
• Format: Article
• Language: English
• Subjects: Adult; Altitude; Biomedical and Life Sciences; Biomedicine; Blood; Blood vessels; Blood Volume; Capillaries - physiology; Carbon monoxide; Exercise; Female; Human Physiology; Humans; Hypoxia; Lung - blood supply; Male; Middle Aged; Nitric oxide; Occupational Medicine/Industrial Medicine; Original; Original Article; Oxygen Consumption; Physical fitness; Pulmonary arteries; Pulmonary Circulation; Pulmonary Gas Exchange; Sea level; Sports Medicine
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s00421-015-3299-1

Purpose We determined whether well-acclimatized humans have a reserve to recruit pulmonary capillaries in response to exercise at high altitude. Methods At sea level, lung diffusing capacity for carbon monoxide (DLCO), alveolar-capillary membrane conductance (Dm CO ), and pulmonary capillary blood volume ( V c ) were measured at rest before maximal oxygen consumption ( V ˙ O 2 max ) was determined in seven adults. Then, DLCO, Dm CO and V c were measured pre- and post-exhaustive incremental exercise at 5150 m after ~40 days of acclimatization. Results Immediately after exercise at high altitude, there was an increase in group mean Dm CO (14 ± 10 %, P  = 0.040) with no pre- to post-exercise change in group mean DLCO (46.9 ± 5.8 vs. 50.6 ± 9.6 ml/min/mmHg, P  = 0.213) or V c (151 ± 28 vs. 158 ± 37 ml, P  = 0.693). There was, however, a ~20 % increase in DLCO from pre- to post-exercise at high altitude (51.2 ± 0.2 vs. 61.1 ± 0.2 ml/min/mmHg) with a concomitant increase in Dm CO (123 ± 2 vs. 156 ± 4 ml/min/mmHg) and V c (157 ± 3 vs. 180 ± 8 ml) in 2 of the 7 participants. There was a significant positive relationship between the decrease in V ˙ O 2 max from sea level to high altitude and the change in DLCO and lung diffusing capacity for nitric oxide (DLNO) from rest to end-exercise at high altitude. Conclusion These data suggest that recruitment of the pulmonary capillaries in response to exercise at high altitude is limited in most well-acclimatized humans but that any such a reserve may be associated with better exercise capacity.