Flow-Triggering Does Not Decrease the Work of Breathing and Pressure-Time Product in COPD Patients

Abstract

Background

Because of their resistance, CPAP systems, triggered by a preset pressure change (PT-CPAP), impose a greater work of breathing (WOB) than is imposed by endotra-cheal tubes and circuitry alone. Flow-triggered CPAP (FT-CPAP) has been developed to avoid some of this increase.

Method

With a pulmonary mechanics monitor, we measured and compared WOB and pressure-time product (PTP) with FT-CPAP and PT-CPAP (in the Puritan-Bennett 7200ae) in 7 hemodynamically stable COPD patients who were ready for weaning. Significance of differences in results between the two systems was tested by 2-way re-peated-measures analysis of variance.

Results

Mean (SD) WOB on FT-CPAP was 1.19 (0.31) J/L and on PT-CPAP 1.24 (0.29) J/L (p = 0.79). Mean PTP on FT-CPAP was 251 (88) cm H2Os min-1 and on PT-CPAP 282 (96) cm H2Os min-1 (p = 0.81). No difference in sensitivity as determined by the monitor was seen between PT-CPAP and FT-CPAP.

Conclusion

Our results do not support the superiority of FT- over PT-CPAP in COPD pa-tients being weaned from mechanical ventilation.

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