[Hemodynamic reactions to positive intrathoracic pressure in + Gz overload].

Eight male test subjects, aged 20-28, were exposed to acceleration +Gz and positive breathing pressure (PBP) of 30 mm Hg to study their hemodynamics under these conditions. The calculated and experimental decrease of blood pressure at the eye level during increasing acceleration and voluntary myorelaxation was comparable. The exposure to PBP helped tolerate higher (by 1.1 +/- 0.2 G) acceleration values without visual disorders. The exposure to 7.0 G and PBP caused a lower increase in heart rate and breathing frequency (by 6% and 12%, respectively), a smaller reduction of blood pressure at the eye level (by 20%), and a decreased muscular tension (by 18%).