Lung volumes and ventilatory responses to high CO2 and low O2 in the ama

Various respiratory functions were determined in 20 ama (diving women) as well as in an equal number of nondivers (control group.) The vital capacity was significantly larger in the ama than in the control; this is entirely due to the higher inspiratory capacity in the former group. Neither the residual volume (RV) nor the expiratory reserve volume showed any difference between the two groups. Hence, the RV/TLC ratio tended to be lower in the ama. MBC was considerably higher in the ama. The maximal inspiratory pressure for any given lung volume was significantly higher in the ama, while the maximal expiratory pressure was not different between the two groups. The resting alveolar gas composition is not different from that of the control. The ventilatory responses to breathing 3% and 5% CO2 in O2, as well as the ventilatory responses to breathing 8.5% O2 in N2, were measured and are discussed. It is suggested that some of these differences in pulmonary function between the ama and control group represent long-term adaptations of the divers acquired by engaging daily in diving operations.