Am. J. Respir. Crit. Care Med.,
Volume 157, Number 4, April 1998, 1085-1092
Diaphragm Function during Sighs in Awake
Dogs after Laparotomy
HISAKO
KATAGIRI,
MASATO
KATAGIRI,
TERESA M.
KIESER,
and
PAUL A.
EASTON
Division of Critical Care, Department of Medicine, University of Calgary, Calgary, Alberta, Canada
Pulmonary complications after upper abdominal surgery are usually ascribed to temporary postoperative impairment of diaphragm function, which may not originate from intrinsic, structural injury but
from reflex inhibition of diaphragm contractility. Spontaneous breathing is interrupted periodically
by sighs, even after upper abdominal surgery. If postoperative dysfunction of the diaphragm arises
from a reflexic inhibition, then the sigh should temporarily override the inhibition and restore normal diaphragm function. We implanted sonomicrometer and electromyogram transducers chronically in six dogs by laparotomy, then directly measured length, shortening, and electromyogram activity of costal and crural diaphragm segments, parasternal intercostal, and transversus abdominis
muscles an average of 8.7 (range, 1-16) d later during resting tidal breathing and sighs. In each animal we analyzed a sequence of breaths, including a sigh, when costal or crural diaphragm contractility was abnormal. With each sigh, the shape and amplitude of costal and crural diaphragm segmental
shortening improved abruptly, from 0.9 and 1.4% of baseline length (% LBL) during resting breathing to 12.1 and 11.1% LBL, respectively, during sighs. The sighs were compared to CO2-stimulated breaths of equivalent tidal volume, which did not show either pattern or amplitude of shortening
equivalent to sighs. We conclude that diaphragm dysfunction after laparotomy arises from a reflex inhibition, which is overridden abruptly to return diaphragm function briefly to normal during each
spontaneous sigh.
