Measurement of static and dynamic pulmonary work during pressure breathing
Morrison, J.B.; Taylor, N.A.
Undersea Biomedical Research 17(5): 453-467
1990
ISSN/ISBN: 0093-5387 PMID: 2219553 Document Number: 361753
Various environments alter static and flow-resistive pulmonary mechanics. Of interest to diving physiologists is the negative pressure breathing induced during upright immersions without appropriate modification of air supply pressure. This paper outlines methodologic considerations for determining static and flow-resistive pulmonary work under such exposures. Ten males performed inspiratory pressure-volume relaxation maneuvers and spontaneous breathing in air, and during upright immersion with mouth pressure air supply. The immersed lung centroid pressure (PLC) was +1.19 kPa relative to the hydrostatic pressure at the sternal notch. Immersion elevated inspiratory static work from 0.36 to 1.74 J .cntdot. liter-1 (P < 0.05). Pulmonary flow-resistive work was elevated from 0.20 to 0.75 J .cntdot. liter-1 (P < 0.05), whereas pulmonary resistance, determined at 0.5 liter .cntdot. sec-1, increased from 0.18 to 0.44 kPa .cntdot. liter-1 .cntdot. sec (P < 0.05). No significant changes in the iso-volume compliance of the lung tissue, chest wall, or total respiratory system were observed (P > 0.05). Results indicate that increases in the work of breathing are due to a combination of hydrostatic pressure imbalance, increased pulmonary resistance, and reduced end-expiratory total respiratory compliance.