Pulmonary and Circulatory Effects of Acute Pulmonary Vascular Engorgement in Normal Subjects 1

Abstract

Brief, acute central and pulmonary vascular engorgement was induced in normal subjects by application of pressure to the body surface. This was done either by inflation of an aviator''s G suit to 2 psi or by submersion in water while breathing against atmospheric pressure. G suit inflation produced in 15 subjects an increase in central venous pressure of 26.8 (S.D. 7.8) cm H2O and a fall in compliance from the control value of .217 [plus or minus] .048 I/cm H2O to .093 [plus or minus] .036 l/cm H2O. A similar compliance fall occurred with submersion. On maintaining G suit pressure or submersion for a 2-minute period, central venous pressure and compliance showed a progressive, but incomplete, return toward control levels. Infusion of norepinephrine or immersion of an arm in ice water during this time prevented the return of venous pressure and compliance toward control levels. Administration of norepinephrine or immersion of an arm in ice water without suit inflation caused a moderate increase in central venous pressure and a moderate decrease in compliance. When the G suit was inflated during norepinephrine infusion, the resultant elevation of central venous pressure and the drop in compliance were greater than in untreated subjects. Pre-treatment with hexamethonium diminished the rise in central venous pressure which occurred with suit inflation, but did not affect the compliance changes. It is suggested that the compliance changes induced by these procedures depend, at least partially, on varying degrees of pulmonary vascular engorgement and that this, in turn, is partially dependent, under the present experimental conditions, on peripheral venous tone.