Ventilatory response and pattern of breathing during hypercapnia.

In an attempt to narrow the definition of normal ventilatory response to hypercapnia (SVE), we studied 105 healthy Caucasians, aged from 18 to 80 years and living at sea level. The mean and SD of SVE were 2.18 +/- 0.77 1 X min-1 X mmHg-1 in males and 1.70 +/- 0.74 in females, narrower than the ranges previously reported. The 95% tolerance limits were 0.491-3.735 and 0.241-2.963 respectively. SVE was correlated with height, body surface area, static and dynamic lung volumes (p less than 0.01), age and weight (p less than 0.05). A prediction formula for SVE was derived on the basis of FEV1, which of the above parameters best correlated with SVE. The separate measurement of the tidal volume and frequency changes (SVT, Sf and SVT/Sf) showed that the SVT and SVT/Sf were significantly higher in males than in females even after adjustment for lung volume (p less than 0.01 and p less than 0.02 respectively), suggesting a different pattern of response to hypercapnia between the sexes.