Pulmonary gas exchange is not impaired 24 h after extravehicular activity

• Published in: Journal of applied physiology (1985) Vol. 99; no. 6; pp. 2233 - 2238
• Main Authors: Prisk, G. Kim, Fine, Janelle M, Cooper, Trevor K, West, John B
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.12.2005; American Physiological Society
• Subjects: Adaptation, Physiological - physiology; Adult; Biological and medical sciences; Extravehicular Activity - physiology; Female; Fundamental and applied biological sciences. Psychology; Gas exchange; Gases; Gravity; Humans; Lungs; Male; Oxygen Consumption - physiology; Pulmonary Gas Exchange - physiology; Respiratory function; Respiratory system; Stress; Ventilation; Weightlessness; Vertebrata; Mammalia; Perfusion; Lung; Ratio; decompression; venous gas emboli; ventilation-perfusion ratio; Gas exchange; Pulmonary ventilation; Respiration; Respiratory system
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00847.2005

Department of Medicine, University of California, San Diego, La Jolla, California Submitted 14 July 2005 ; accepted in final form 23 August 2005 Extravehicular activity (EVA) during spaceflight involves a significant decompression stress. Previous studies have shown an increase in the inhomogeneity of ventilation-perfusion ratio ( A / ) after some underwater dives, presumably through the embolic effects of venous gas microemboli in the lung. Ground-based chamber studies simulating EVA have shown that venous gas microemboli occur in a large percentage of the subjects undergoing decompression, despite the use of prebreathe protocols to reduce dissolved N 2 in the tissues. We studied eight crewmembers (7 male, 1 female) of the International Space Station who performed 15 EVAs (initial cabin pressure 748 mmHg, final suit pressure either 295 or 220 mmHg depending on the suit used) and who followed the denitrogenation procedures approved for EVA from the International Space Station. The intrabreath A / slope was calculated from the alveolar P O 2 and P CO 2 in a prolonged exhalation maneuver on the day after EVA and compared with measurements made in microgravity on days well separated from the EVA. There were no significant changes in intrabreath A / slope as a result of EVA, although there was a slight increase in metabolic rate and ventilation ( 9%) on the day after EVA. Vital capacity and other measures of pulmonary function were largely unaltered by EVA. Because measurements could only be performed on the day after EVA because of logistical constraints, we were unable to determine an acute effect of EVA on A / inequality. The results suggest that current denitrogenation protocols do not result in any major lasting alteration to gas exchange in the lung. decompression; ventilation-perfusion ratio; venous gas emboli Address for reprint requests and other correspondence: G. K. Prisk, Division of Physiology, Dept. of Medicine, Univ. of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0931 (e-mail: kprisk{at}ucsd.edu )