Voluntary Breathholding. Iii. The Relation of the Maximum Time of Breathholding to the Oxygen and Carbon Dioxide Tensions of Arterial Blood, With a Note on Its Clinical and Physiological Significance 1

By means of underwater weighing during breathholding, after preliminary inhalation of gas mixtures containing varying concentrations of oxygen, it has been shown that the diffusion of oxygen from the lungs is influenced by the PO2 of the inspired air (1). It was also shown (2) that the duration of the maximum voluntary breathholding time was related to the PO2 of in- spired air. Others have shown that alveolar pCO2 plays an important role in altering the breathholding time (3 to 5). Thus, it is evident that both PO2 and pCO2 are factors which influ- ence the time that the breath can be held. Sev- eral investigators (6, 3) have studied alveolar gases during breathholding, and at the end of the apneic period produced by hyperventilation, but to our knowledge, the changes in the arterial blood have not been investigated. Despite the lack of knowledge concerning the physiologic changes which occur during breathholding, it is being used with increasing frequency as a clinical test (7 to 9).