Journal of Applied Physiology, Vol 44, Issue 4 538-541, Copyright © 1978 by American Physiological Society
Maximal frequency of breathing at various tidal volumes in airways obstruction
L. Marazzini, L. Gatti, R. Cavestri and E. Longhini
To determine the relative importance of control system and of mechanical
and metabolic properties of the motor system on the maximal frequency of
breathing (1/t) at various tidal volumes (VT), we have studied the
relationship between cycle period (t) and tidal volume in 10 normal
subjects, in 9 patients with chronic obstructive lung disease, and in a
normal subject breathing against different resistive loads. The results,
expressed according to the equation t = t0 + b VT (where t0 represents the
time required for a breathing cycle at zero VT and b means the additional
time required for a breathing cycle with a VT equal to vital capacity),
indicate that t0 is independent from the load either in unloaded or loaded
normal subjects or in obstructive patients. In fact, although b was found
significantly different, t0 remained essentially constant. These findings
suggest that the level of maximal voluntary ventilation may be mainly
related to metabolic and mechanical properties of the motor system (muscles
of breathing and load imposed on them).
