Journal of Applied Physiology, Vol 47, Issue 1 119-125, Copyright © 1979 by American Physiological Society
Breathing responses of unanesthetized man and guinea pigs to increased transrespiratory pressure
J. R. Gillespie, E. Bruce, J. Alexander and J. Mead
We compared the breathing responses of unanesthetized men and guinea pigs
to externally imposed shifts in lung volume produced by steady pressures
applied to the body surface while the mouth remained near atmospheric
pressure. Lung inflation caused no consistent or significant changes either
in frequency or end-tidal CO2 in the three men. In contrast, during lung
inflation the guinea pigs breathed at low frequencies and smaller tidal
volumes and showed consistent increases in arterial PCO2 lasting up to 10
min. The changes seen immediately on application of pressure, namely apneic
periods followed by breathing in which inspiratory duration was shortened
while expiratory duration was substantially increased, indicates that
conscious guinea pigs have active inflation reflexes. We concluded that the
reflex responses rather than mechanical factors probably account for the
underventilation in the guinea pigs and that guinea pigs are not nearly as
well equipped as is man to defend gas exchange in the face of nonmetabolic
shifts in lung volume.
