Published in:
01-06-2003 | Original
Respiratory muscle workload in intubated, spontaneously breathing patients without COPD: pressure support vs proportional assist ventilation
Published in: Intensive Care Medicine | Issue 6/2003
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Objective
To compare the respiratory muscle workload associated with pressure support ventilation (PSV) and proportional assist ventilation (PAV) in intubated and spontaneously breathing patients without COPD.
Design and setting
Prospective study, intensive care unit university hospital.
Interventions
Twenty intubated patients, during early weaning, PSV settings made by clinician in charge of the patient, and two levels of PAV, set to counterbalance 80% (PAV 80) and 50% (PAV 50) of both elastic and resistive loads, respectively. The patients were ventilated in the following order: 1) PSV; 2) PAV 50 or PAV 80; 3) PSV; 4) PAV 80 or PAV 50; 5) PSV. PSV settings were kept constant.
Measurements
Arterial blood gases, breathing pattern and respiratory effort parameters at the end of each of the five steps.
Main results
PSV and PAV 80 had the same effects on work of breathing (WOB). The pressure-time product (PTP) was significantly higher during PAV 80 than during PSV (90±76 and 61±56 cmH2O·s·min-1, respectively, P <0.05). Tidal volume was comparable, albeit more variable with PAV 80 than with PSV (variation coefficient, 43% vs 25%, respectively, P <0.05). PAV 50 entailed a higher respiratory rate, lower tidal volume, and higher WOB and PTP than PSV and PAV 80. PaO2/FiO2 and SaO2 were lower with PAV 50 than with PSV and PAV 80.
Conclusion
In a group of intubated spontaneously breathing non-COPD patients, PAV 80 and PSV were associated with comparable levels WOB, whereas PTP was higher during PAV 80. PAV 50 provided insufficient respiratory assistance.