ENDTIDAL PARTIAL PRESSURES, OXYGEN UPTAKE AND CARBON DIOXIDE OUTPUT FOLLOWING APNEIC DIVING AND BREATH HOLD IN WATER AND IN AIR

Investigations were performed in order to find out whether breathhold or apneic diving will alter oxygen consumption and CO2 production in mam. Therefore 6 male subjects stopped breathing for periods of 30, 60, 90, 120 and 165 sec either outside or immersed in water. The endtidal PO2 and PCO2, the oxygen uptake and CO2 output of each tidal were determined by means of an integrating pneumotachograph and a mass spectrometer in the recovery period. The measured dates were compared with those of diving at the bottom of the swimming pool in a depth of 80 cm. The real oxygen debt which was incurred during apnea was compared with the theoretical oxygen debt which could be calculated from the energy consumption of the preperiod, assumed that the metabolic rate would remain constant during apnea. The O2 consumption was reduced up to 38% during breath holding in air, up to 29% during breath holding immersed in water and up to 28% during diving. The endtidal PO2 of the first exspiration after apnea decreased as a function of the apneic time. After equal periods of apnea the PO2 was lower in the diving than in the breath hold experiments. Up to 90 sec of apnea the CO2 output corresponded to the CO2 production. With increasing apneic time a marked CO2 retention could be observed. The endtidal PCO2 and the CO2 output of the first expiration were independent from apneic time and were found to have a value of about 45 mm Hg and 150 ml respectively. No difference between diving and breath hold could be noticed. © 1969 Springer-Verlag.