AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 2 292-R300, Copyright © 1992 by American Physiological Society
Entrainment of respiratory rhythm by periodic lung inflation: effect of airflow rate and duration
S. Muzzin, P. Baconnier and G. Benchetrit
Laboratoire de Physiologie, Faculte de Medecine de Grenoble, La Tronche, France.
In anesthesized, paralyzed, and mechanically ventilated rabbits, the rate
and duration of airflow were varied to investigate the effect on the
central respiratory rhythm during 1:1 entrainment (1 phrenic nerve burst
for 1 pump inflation). Our results showed that 1) the largest range of 1:1
entrainment was obtained with the longest inflation durations associated
with the lowest flow rates and 2) both inspiratory (TI) and expiratory (TE)
durations (as estimated by the period of phrenic nerve activity and phrenic
nerve silence, respectively) increased when total respiratory duration (TT
= TI+TE) increased. The phase relationships we studied were DI (the time
elapsing between the onset of phrenic activity and the beginning of pump
inflation) and DE (the time between the end of phrenic activity and the end
of pump inflation). Both DI and DE increased when the total ventilatory
period increased. However, for constant ventilatory period, DI changed with
the rate and duration of airflow, whereas DE remained constant. In
addition, under these conditions, TI, TE, and the integrated phrenic nerve
activity remained constant independently of airflow rate and duration. The
present results are discussed with regard to the pulmonary receptors
(slowly and rapidly adapting receptors and C fibers) that are stimulated
during mechanical ventilation, and hypotheses are drawn regarding their
possible contribution to rhythm generation and the mechanism through which
they may act.
