An experimental study of death in a reverse suspension.

To investigate the course of respiration and circulation in a head-down position, 14 rabbits were set in reverse suspension. The respiratory rate increased a little, but the amplitude of the respiratory movements did not change in the beginning of the experiment. The amplitude of respiratory movements then began to reduce gradually, and toward the end of the experiment, it reduced suddenly. PaO2 increased in the beginning of the experiment and then began to decrease in accordance with the reduction of the amplitude of the respiratory movements. The blood pressure decreased with relation to the decrease of PaO2 resulting from the reduction of the amplitude of the respiratory movements. All rabbits died in 17 to 44 hours (average, 26 hours). The results suggested that the cause of death in a head-down position is due to postural asphyxia resulting from hindered respiratory movements, and that it is possible to survive for at least half a day in a head-down position.