Cardiovascular responses of man exposed to +Gz accelerations in a centrifuge.

Cardiovascular investigations were conducted in male volunteer subjects exposed to +Gz accelerations. Some of them did not have any previous experience of the centrifuge. Electrocardiogram, blood pressure, heart rate, stroke volume, and cardiac output were recorded. Accelerations ranging from +1.5 Gz to +6 Gz were applied during periods of from 30 s to 20 min. Acceleration was achieved in 10-90 s. Heart rate markedly increased as a function of acceleration intensity, reaching 160 beats/s. Decreases in cardiac output (30-40%) and stroke volume were also observed. Protection by an anti-G suit reduces tachycardia. Accelerations induce various electrocardiographic disorders lasting several minutes after the stress has been stopped. These are sometimes the first symptoms of functional cardiovascular failure. The centrifuge turns out to be an excellent screening tool. However, when used for testing various aircrew equipment, strict monitoring of the subjects is required.