Effect of series of resistance levels on flow limitation in mechanically ventilated COPD patients

In severe chronic obstructive pulmonary disease (COPD) lung emptying is dis turbed by airways compression and expiratory flow limitation. Application o f an external resistance has been suggested to counteract airways compressi on and improve lung emptying. We studied the effect of various resistance l evels on lung emptying in mechanically ventilated COPD patients. In 18 pati ents an adjustable resistor was applied. The effect on airways compression was assessed by iso-volume pressure-flow curves (IVPF) and by interrupter m easurements. Respiratory mechanics during unimpeded expirations were correl ated to the results obtained with the resistances. The resistances caused a n increase in iso-volume flow at the IVPF-curves in six patients, indicatin g that airways compression was counteracted. Interrupter measurements showe d that overshoots in flow (as measure of flow limitation) were significantl y reduced by the resistor. These effects could be predicted on basis of res piratory mechanics during unimpeded expiration. In conclusion. mechanically ventilated COPD patients can be identified in whom application of external resistances counteracts airways compression and reduces flow limitation. ( C) 2001 Elsevier Science B.V. All rights reserved.