HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 106/2/678    most recent 91099.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Foster, P. P. Articles by Butler, B. D. Search for Related Content PubMed PubMed Citation Articles by Foster, P. P. Articles by Butler, B. D.

REVIEW

HIGHLIGHTED TOPIC
The Physiology and Pathophysiology of the Hyperbaric and Diving Environments

Decompression to altitude: assumptions, experimental evidence, and future directions

¹Department of Internal Medicine, Division of Pulmonary Medicine, Critical Care, and Allergy, University of Texas Medical Branch, Galveston; and ²Department of Anesthesiology, University of Texas Medical School, Houston, Texas

ABSTRACT

Although differences exist, hypobaric and hyperbaric exposures share common physiological, biochemical, and clinical features, and their comparison may provide further insight into the mechanisms of decompression stress. Although altitude decompression illness (DCI) has been experienced by high-altitude Air Force pilots and is common in ground-based experiments simulating decompression profiles of extravehicular activities (EVAs) or astronauts' space walks, no case has been reported during actual EVAs in the non-weight-bearing microgravity environment of orbital space missions. We are uncertain whether gravity influences decompression outcomes via nitrogen tissue washout or via alterations related to skeletal muscle activity. However, robust experimental evidence demonstrated the role of skeletal muscle exercise, activities, and/or movement in bubble formation and DCI occurrence. Dualism of effects of exercise, positive or negative, on bubble formation and DCI is a striking feature in hypobaric exposure. Therefore, the discussion and the structure of this review are centered on those highlighted unresolved topics about the relationship between muscle activity, decompression, and microgravity. This article also provides, in the context of altitude decompression, an overview of the role of denitrogenation, metabolic gases, gas micronuclei, stabilization of bubbles, biochemical pathways activated by bubbles, nitric oxide, oxygen, anthropometric or physiological variables, Doppler-detectable bubbles, and potential arterialization of bubbles. These findings and uncertainties will produce further physiological challenges to solve in order to line up for the programmed human return to the Moon, the preparation for human exploration of Mars, and the EVAs implementation in a non-zero gravity environment.

bubble; decompression illness; exercise; microgravity

This article has been cited by other articles:

				D. R. Pendergast and C. E. G. Lundgren The physiology and pathophysiology of the hyperbaric and diving environments J Appl Physiol, January 1, 2009; 106(1): 274 - 275. [Full Text] [PDF]