Effect of accumulation of CO2 on the survival of immature pigs in a confined atmosphere. B: Blood gas exchange.

As part of a study for developing survival strategy for humans in a confined space, we used immature pigs to assess the applicability of findings in rats and to evaluate the effect of body size. The cannulated unanesthetized animal was placed in a sealed chamber and depleted the oxygen until hypoxic collapse. Three groups were: no accumulation of CO2, CO2 maintained at 5%, and maximal accumulation of CO2. In hypoxia arterial and venous oxygen tension were higher in the pigs exposed to CO2 than in the no CO2 pigs. Oxygen extraction increased and oxygen transport decreased in hypoxia in the presence of CO2. Similarity in the P50 of the oxygen dissociation curve may explain the similar terminal PIO2 in the pig and the rat. There was a positive correlation between terminal PIO2 and terminal venous pH.