Physiologic effects of the position of the body in experimental unilateral emphysema.

The functional residual capacity (FRC), static compliance (Cst) of the respiratory system, minute ventilation, and arterial blood gas levels were studied in the prone, the suprine, and the right and left lateral decubitus positions in dogs with papain-induced emphysema of the right lung alone and were compared with control values. The FRC and Cst of the respiratory system were significantly increased in experimental animals in all four positions, as compared with controls. This was due entirely to increases in FRC and Cst for the right lung alone; for the unexposed left lung the FRC and Cst were significantly reduced, as compared to controls. The mean arterial oxygen tension (PaO2) was decreased in all positions, except the right lateral decubitus position, in which the mean PaO2 was not different from controls. This model demonstrates that in unilaterally distributed, experimentally induced emphysema, alterations alterations in the position of the body alone may significantly alter the FRC, Cst, and gas exchange either favorably or unfavorably, depending upon the position.