A water-filled body plethysmograph for the measurement of pulmonary capillary blood flow during changes of intrathoracic pressure

Abstract

A B S T R A C T A water-filled body plethysmograph was constructed to measure gas exchange in man. As compared to an air-filled plethysmograph, its advantages were greater sensitivity, less thermal drift, and no change from adiabatic to isothermal conditions after a stepwise change of pressure. When five subjects were completely immersed within it and were breathing to the ambient atmosphere, they had a normal heart rate, oxygen consumption, CO2 output, and functional residual capacity. Pulmonary capillary blood flow (0c)

Effects of intrathoracic pressure, inhalation time, and breath hold time on lung diffusing capacity

“…The reason for the reversal of which intrathoracic pressure condition yielded a greater Vc value between rest and exercise is unclear. At rest and during exercise, performing a Valsalva maneuver (positive intrathoracic pressure) has been shown to reduce pulmonary capillary blood flow and Vc, whereas a negative intrathoracic pressure increases Vc (Kawakami et al, 1970; Kowallick et al, 2014; Smith and Rankin, 1969). Theoretically, it is possible that venous return is impeded less during exercise than at rest during a positive intrathoracic pressure condition.…”