DISTRIBUTION OF PULMONARY BLOOD FLOW AS AFFECTED BY TRANSVERSE (+GX) ACCELERATION.

The distribution of blood flow in the pulmonary vascular bed under Gx forward or transverse acceleration was studied by the intravenous injection of radioactive 131 Iodinated-macro aggregated albumin 131I-MAA in three normal subjects while they were under 1Gx, 4Gx and 8Gx on a human centrifuge. The resulting distribution of radioactivity in the lungs, representing the distribution of pulmonary blood flow at the time of injection, was assessed one to three hours later by lateral radioisotope scanning. The distribution of pulmonary blood flow was not markedly different at 1Gx, 4Gx, and 8Gx despite a hydrostatic gradient in pulmonary intravascular pressures estimated to be 88 mm Hg under 8Gx. These findings indicate that under Gx forward or transverse acceleration unlike Gz headward or positive acceleration the distribution of pulmonary blood flow is not markedly distorted, and that the regional flow of blood in the lung may not be significantly changed by high intravascular pressures. Author