FLOW LIMITATION IN ANESTHETIZED RHESUS-MONKEYS - A COMPARISON OF RAPID THORACOABDOMINAL COMPRESSION AND FORCED DEFLATION TECHNIQUES

Rapid thoracoabdominal compression (RTC) and forced deflation (FD) all ow the examination of maximal expiratory flow-volume (MEFV) curves in animals and human infants unable to generate a voluntary maximal expir atory maneuver. We compared flows generated by these two techniques an d by constructing isovolume pressure-flow (IVPF) curves examined each method's potential to produce flow limitation. RTC and FD were perform ed in seven intubated rhesus monkeys from +40 cm H2O inspiratory press ure with deflation pressures ranging from -20 to -100 cm H2O and jacke t pressures from +20 to +100 cm H2O (arms outside jacket). We also per formed RTC maneuvers in all monkeys with the arms inside the jacket at + 100 cm H2O jacket pressure. Maximal expiratory flows achieved by FD and RTC were analyzed at isovolume points. Both techniques produced f low limitation conditions over the last 25% of the MEFV curve, Individ ual IVPF curves generated by the two techniques demonstrated remarkabl e differences in shape and flow rates. Maximal transpulmonary pressure s achieved with FD were higher than those with RTC in this experiment. Negative effort dependence was observed with higher deflation pressur es in the majority of the monkeys. Flows achieved by RTC with the arms in were lower than those achieved with the arms out when compared at identical pressure gradients. We conclude that the difference in expir atory flow rates at isovolume-pressure points is most likely related t o different effects on the behavior of intrapulmonary airways and chok e point characteristics by the two techniques.