Journal of Applied Physiology, Vol 54, Issue 4 1131-1140, Copyright © 1983 by American Physiological Society
Ventilation-perfusion relationships after hemorrhage and resuscitation: an inert gas analysis
N. B. Robinson, E. Y. Chi and H. T. Robertson
Previous investigations suggest that ventilation-perfusion (VA/Q)
relationships after hemorrhagic shock are primarily dependent on regional
distribution of pulmonary blood flow and implicated early VA/Q
heterogeneity secondary to disproportionate redistribution of pulmonary
blood flow to dependent lung regions. Multiple inert gas elimination
analysis, as described by Wagner et al. (J. Appl. Physiol.: Respirat.
Environ. Exercise Physiol. 36: 588-599, 1974), was applied to a standard
hemorrhagic shock preparation to test this hypothesis. Soon after
hemorrhage, VA/Q distributions shifted homogeneously into high VA/Q
compartments, preserving base-line VA/Q relationships around a new mean
VA/Q ratio. Although the mean VA/Q and VA/Q distribution returned to base
line after resuscitation with autologous blood, absolute dead space
ventilation persisted. Gas exchange defects included increased Bohr dead
space ventilation, which could be attributed to 1) a homogeneous shift of
VA/Q distributions into high VA/Q compartments, and 2) new absolute dead
space ventilation associated with observed intravascular leukostasis and
vascular occlusion. In contrast to previous investigations, these data
suggest that VA/Q heterogeneity does not occur after hemorrhage, but rather
pulmonary blood flow decreases proportionately throughout all lung regions,
preserving base-line VA/Q patterns around a new mean VA/Q ratio.
