Journal of Applied Physiology, Vol 66, Issue 6 2496-2501, Copyright © 1989 by American Physiological Society
Effects of abdominal opening on respiratory system mechanics in ventilated rats
W. A. Zin, M. A. Martins, P. R. Silva, R. S. Sakae, A. L. Carvalho and P. H. Saldiva
Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
In 16 anesthetized paralyzed mechanically ventilated rats, respiratory
system mechanics and rib cage dimensions were determined both before and
after wide abdominal opening. In eight animals the end-inflation occlusion
method disclosed statistically significant postoperative increases in
respiratory system elastance (from 4.84 to 6.49 cmH2O.ml-1) and resistance
(from 0.224 to 0.300 cmH2O.ml-1.s); the latter resulted from a rise of its
uneven component (from 0.161 to 0.209 cmH2O.ml-1.s). In the remaining rats,
rib cage morphometry at functional residual capacity after surgery showed
significant decreases in lower rib cage circumference and anteroposterior
and lateral diameters, whereas there was an increase in upper rib cage
circumference and a fall in its lateral diameter. When these parameters
were measured at end-inspiratory lung volume, the difference between intact
and open abdomen were less striking; only lower rib cage circumference and
upper rib cage lateral diameter significantly decreased postoperatively.
Because surgery induced an expiratory volume of only 0.1 ml, it can be
concluded that abdominal opening redistributed regional volumes within the
lung, leading to increased unevenness in the system.
