Effect of sequential anti-G suit inflation on pulmonary capillary blood flow in man.

The hemodynamic effects of an anti-G suit, sequentially filled from below upward (M-aG), were compared to those of the standard USAF anti-G suit (S-aG) in 10 men supine and under +1 Gz stress produced by 90 degrees head up passive tilt. S-aG was found to fill from the abdominal bladder downward. The heart rate and the pulmonary capillary blood flow (Qc), as estimated by a nitrous oxide plethysmographic method, were used as criteria of effectiveness. Heart rate did not vary between the suits during the supine and upright studies. In the supine position, the first M-aG inflation induced a significant increase of Qc, 2.5 1 min above the Qc of the S-aG inflation. After 90 degrees head up tilt, M-aG inflation as associated with a significant increase of Qc, 1.7 1 min greater than the Qc produced by S-aG inflation. Since leg bladder inflation may play a critical role in high-G tolerance, the sequential filling from below upward of the anti-G suit may further increase the G protection compared to the standard garment. In addition, the modified anti-G suit may be a useful device for treatment of circulatory shock and postural hypotension when the venous return is decreased.