Journal of Applied Physiology, Vol 50, Issue 6 1318-1324, Copyright © 1981 by American Physiological Society
Lung compliance and its transient elevations measured with pulse-flow method
P. M. Suratt, D. H. Owens, H. Hsiao, D. L. Kaiser and D. F. Rochester
We describe a pulse-flow method of measuring static lung compliance (CL)
that is sensitive to rapid transients in CL. CL is measured by blowing air
at a constant flow into the mouth and lungs for 2 s and calculated by
dividing airflow in 1/s by the change in transpulmonary pressure in
CMH2O/s. Pulse and static inspiratory CL was measured in five normals, four
obstructives, five obese, and two patients with pulmonary fibrosis, Pulse
CL after tidal breathing was correlated with static CL measured after deep
breaths (r = 0.96). Pulse CL after deep breaths was higher than pulse CL
after tidal breathing (p less than 0.01) and then static CL after deep
breaths (p less than 0.05). In all subjects the lower the forced expiratory
volume in 1 s, expressed as a percentage of vital capacity (FEV1/FVC), the
greater the increase in pulse CL after a deep breath will be (r = 0.93).
After deep breaths pulse CL fell from maximum CL to base-line CL at a rate
related to 1/t2 where t equals the time in seconds from the last deep
breath. We conclude that the increase in CL after a deep breath is related
to the degree of airway obstruction and that the subsequent fall in CL is
related to 1/t2.
