1974 Volume 112 Issue 1 Pages 3-13
Effects of voluntary submaximal ventilatory drive on the pulmonary circulation were studied under the right and left cardiac catheterizations in 10 patients. In supine position, the patient was forced to make a voluntary deep inspiration of the duration of at least 20 seconds, and succeedingly deep expiration of the same duration while pulmonary artery (PA), left atrial (LA) and intraesophageal pressures were recorded continuously. The dye-dilution curve was recorded from the left atrium after injection of indocyanine green into the main pulmonary artery at 10 seconds from the start of the ventilatory maneuver, for measurement of cardiac output, mean transit time and pulmonary blood volume. Mean pressure difference between PA and LA significantly increased in inspiration and decreased to a value slightly lower than resting ventilation value in expiration. Pulmonary vascular resistance increased in inspiration but did not show a consistent change in expiration. Pulmonary blood volume tended to increase in inspiration and to decrease in expiration. It is suggested that the increased PA-LA pressure difference during inspiration would be due to a reduction in the capacity of small-sized pulmonary vessels adjacent to the alveoli by lung inflation which are acting as resistance vessels of pulmonary circulation, so that pulmonary vascular resistance is increased.
