Journal of Applied Physiology, Vol 38, Issue 1 46-51, Copyright © 1975 by American Physiological Society
Effects of atropine on natural deflation flows and P-V curves of the isolated lung lobe
E. Goldman and R. J. Puy
Static pressure-volume (P-V) curves and natural deflation flows (NDF) in
isolated dog's lung lobes were obtained before and after atropine. Since
elastic pressure was the driving force for the expiratory flow this
preparation was devoid of the influence of compressive forces. A
significant shift to the left of the P-V curve was observed after atropine.
Mean increase in volume in the range from 30 to 2 cmH2O transpulmonary
pressure (Ptp) was 0.6 ml/g (about 4% increase in percent of maximal lung
volume MLV). NDF at the same Ptp (referred to as airway conductance) were
significantly higher after atropine (mean increase 3 ml/s per g, about 0.15
l/s). Increase in lung volume after atropine was interpreted as evidence of
relaxation of residual bronchomotor tone which in turn, by increasing
airway diameters, may produce higher flows. When NDF were plotted against
volume, differences between control and atropine were reduced. This was
attributed to the observed leftward displacement of the P-V curve. The
linear relationship found between NDF and volume in the range 2-8 cmH2O of
Ptp (about 35-75% MLV) suggests a proportionate change in airway
conductance with lung size. This could indicate that the lobes behaved
homogeneously during passive deflation. This pattern was not modified by
atropine.
