Circulatory Studies During Artificial Respiration on Apneic Normal Adults. III

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Abstract
To evaluate the efficacy of various methods of artificial respiration, the arterial oxyhemoglobin levels,'' cardiac output and pressure changes in the right auricle, right ventricle, pulmonary and femoral arteries were studied in 15 normal adult male volunteers, rendered totally apneic with barbiturate-curare-mixtures. The Schafer Prone Pressure, Hip-Lift Back-Pressure (HLBP), Arm-Lift Back-Pressure (ALBP), Hip-Roll Back-Pressure (HRBP), and Eve Rocking Methods were studied. Right heart catheterization technic was used for cardiac output and pressure measurements. The Schafer method had to be discontinued in 3 out of 9 cases because of alarming cyanosis. The arterial oxygen saturation in the remaining cases varied from 42 to 96% and that in the mixed venous blood from 22 to 60%. The A-V oxygen difference varied from 14 to 35%. All remaining methods maintained arterial saturations between 88-100% and the A-V oxygen differences were from 9-30%. The arterial oxyhemoglobin was not found to be directly correlated with the minute ventilation. It is concluded from minute ventilation, R.Q. and hemoglobin saturation that marked variations in alveolar ventilation/flow have been present. Analysis of pressure curves and of pulse pressures, in particular, points to markedly decreased stroke volumes during the pressure phases of the artificial respiratory cycles. The right ventricle seems to be affected more than the left one. The diastolic pressures in the right ventricle and pulmonary artery increased 15-25 mm. of mercury pressure during the back-pressure phases. A similar rise of pressure was observed in the right auricle. The impairment of filling during the pressure phase did not have any appreciable effect on cardiac output, which was maintained at high levels. The avg. cardiac outputs (liters/min./100 ml. O2 consumed) were: Schafer- 2.2; HLBP[long dash]2.58; ALBP[long dash]2.56; HRBP[long dash]2.42; and Eve[long dash]2.7. It is concluded that the Schafer method is greatly inferior in maintaining a satisfactory HbO2 level and should be replaced by one of the other methods described. There is no substantial difference between the other individual methods of the "push-pull" type, and Eve''s mechanical rocker.