Respiratory muscle workload in intubated, spontaneously breathing patients without COPD: pressure support vs proportional assist ventilation

Delaere, Stéphanie; Roeseler, Jean; D'hoore, William; Matte, Pascal; Reynaert, Marc; Jolliet, Philippe; Sottiaux, Thierry; Liistro, Giuseppe; Delaere, Stéphanie
June 2003
Intensive Care Medicine;Jun2003, Vol. 29 Issue 6, p949
Academic Journal
journal article
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 cmH(2)O.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. PaO(2)/FiO(2) and SaO(2) 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.


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