Progressive and transient hypoxic ventilatory drive tests in healthy subjects.

In order to ascertain the correlation between progressive and transient hypoxic ventilatory drive tests, 18 healthy subjects were tested by both methods, and the results were compared. Sudden cessation of steady-state hypoxia was done in 9 of the subjects to determine if an exaggerated central depressant effect of hypoxia might occur in some persons during progressive testing and explain a low response to progressive hypoxia. Because the progressive hypoxia test is frequently used in evaluating the effects of therapeutic interventions on ventilatory drive, the reproducibility of this test over time was also evaluated in 10 subjects. THere was a significant correlation between the results of the progressive and transient hypoxic tests when data from 17 of the 18 subjects were compared by linear regression analysis (r = 0.56, p less than 0.05). In 1 of 18 subjects, the ventilatory response to progressive hypoxia was quite low, whereas the response to transient hypoxia was high, and this can possibly be explained by an exaggerated central depressant effect of hypoxia. The progressive hypoxia test is quite reproducible (variance = 0.0092) over a 5- to 7-month period. We conclude that the use of progressive or transient hypoxic ventilatory drive tests will result in similar conclusions regarding the hypoxic ventilatory drive in most persons. In addition, the progressive hypoxia test can be reliably used to evaluate the effects of therapeutic interventions on hypoxic ventilatory drive.