Document Detail

Relative effects of submersion and increased pressure on respiratory mechanics, work, and energy cost of breathing.
MedLine Citation:
PMID:  23305982     Owner:  NLM     Status:  Publisher    
Submersion and increased pressure (depth) characterize the diving environment and may independently increase demand on the respiratory system. To quantify changes in respiratory mechanics, this study employed a unique protocol and techniques to measure, in a hyperbaric chamber, inspiratory and expiratory alveolar pressures (P(AI) and P(AE), interrupter technique), inspiratory and expiratory resistance in the airways (R(awI) and R(awE), esophageal balloon technique), nitric oxide elimination (V(•)(NO), thought to correlate with R(aw)), inspiratory and expiratory mechanical power of breathing ((I) and (E)), and the total energy cost of ventilation. Eight healthy adult males underwent experiments at 1 atmosphere absolute (ATA), 2.7ATA, and 4.6ATA both dry and fully submersed. Subjects rested, cycled an ergometer at 100W, and rested while voluntarily matching their ventilation to their own exercise hyperpnea (ISEV). During ISEV, increased V(•)(O2) (above rest values) resulted from increased V(•)(E). R(awI) decreased with submersion (mean 43% rest, 20% exercise) but increased from 1ATA to 4.6ATA (19% rest, 75% exercise), as did R(awE): 53% decrease with submersion (rest), 10% (exercise); 9% increase from 1 to 4.6ATA (rest), 66% (exercise). V(•)(NO) did not correlate with R(aw). Depth increased (I) during rest (40%) and exercise (20%). (E) was largely unchanged. These results suggest that the diving environment affects ventilatory mechanics primarily by increasing airway resistance, secondary to increased gas density. This necessitates increased alveolar pressure and increases the work and energy cost of breathing as the diver descends. These findings can inform physician assessment of diver fitness and the pulmonary risks of hyperbaric oxygen therapy (HBOT).
Heather E Held; David R Pendergast
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-10
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  -     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-11     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1University of South Florida.
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