Journal of Applied Physiology, Vol 50, Issue 5 1087-1092, Copyright © 1981 by American Physiological Society
Work of breathing in dog during exercise
F. Saibene, P. Mognoni, G. Aguggini and M. G. Clement
In six dogs trained to wear a mask and to swallow an esophageal balloon,
the dynamic work of breathing (Wdyn) was measured while the animals ran on
a treadmill at different intensities (7-13 km.h-1,+10%). Wydn (kg.m.min-1)
increased with ventilation (VE, 1.min-1) according to Wdyn = 0.308.10(-2)
VE2 + 0.0098.10(-2).VE3. However, if the exercise was prolonged so that the
body temperature rose above approximately 39 degrees C, Wdyn, for a given
ventilation, decreased; and hence Wdyn = 0.253.10(-2).VE2 --
0.0011.10(-2).VE3. Similar observations have been made on another dog
heated from an external source. From this finding it seems that during
exercise, when the temperature rises and the ventilation increases to
dissipate heat, the airway size, at least in some portion of the
respiratory tract, increases markedly and therefore the cost of breathing
is greatly diminished.This mechanism would save oxygen for the exercising
limb muscles when exercise has to be continued for an extended time.
