Abstract
A ventilator with an adjustable internal compliance (Cv) has been constructed (Schaller et al 1991). In addition to a baseline “CPAP” it generates a pressure at the endotracheal tube (ETT) proportional to the instantaneous inspired volume. Thus, a decreased compliance of the patient's lung (C1) can theoretically be compensated during spontaneous breathing by adjusting Cv to a negative value. To test this hypothesis we assessed how stepwise changes in Cv influenced the compliance of the combined ventilator-ETT-lung system (Ctot) and integrated inspiratory phrenic nerve activity in 13 chloralose anesthetized cats. Ctot improved according to the relation 1/Ctot = 1/C1+1/Cv. With a time lag of no more than 2 or 3 breathing cycles phrenic nerve activity decreased with elastic unloading to a new level. It decreased in a hyperbolic relation to the percentually scaled improvement in Ctot, both before (r=0.85) and after (r=0.69) lung injury. We conclude that elastic unloading effectively decreases inspiratory activity and work of breathing for a given alveolar ventilation i stiff lungs.
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Jonzon, A., Schulze, A., Schaller, P. et al. 179 PARTIAL MECHANICAL UNLOADING OF THE ELASTIC WORK OF SPONTANEOUS BREATHING IN CATS WITH NORMAL AND XANTIHINEOXIDASE INJURED LUNGS. Pediatr Res 30, 658 (1991). https://doi.org/10.1203/00006450-199112000-00209
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DOI: https://doi.org/10.1203/00006450-199112000-00209