Original Contributions Work of Breathing During Lung-Protective Ventilation in Patients With Acute Lung Injury and Acute Respiratory Distress Syndrome: A Comparison Between Volume and Pressure-Regulated Breathing Modes

BACKGROUND: Pressure-control ventilation (PCV) and pressure-regulated volume-control (PRVC) ventilation are used during lung-protective ventilation because the high, variable, peak inspiratory flow rate (V̇I) may reduce patient work of breathing (WOB) more than the fixed V̇I of volume-control ventilation (VCV). Patient-triggered breaths during PCV and PRVC may result in excessive tidal volume (VT) delivery unless the inspiratory pressure is reduced, which in turn may decrease the peak V̇I. We tested whether PCV and PRVC reduce WOB better than VCV with a high, fixed peak V̇I (75 L/min) while also maintaining a low VT target. METHODS: Fourteen nonconsecutive patients with acute lung injury or acute respiratory distress syndrome were studied prospectively, using a random presentation of ventilator modes in a crossover, repeated-measures design. A target VT of 6.4 0.5 mL/kg was set during VCV and PRVC. During PCV the inspiratory pressure was set to achieve the same VT. WOB and other variables were measured with a pulmonary mechanics monitor (Bicore CP-100). RESULTS: There was a nonsignificant trend toward higher WOB (in J/L) during PCV (1.27 0.58 J/L) and PRVC (1.35 0.60 J/L), compared to VCV (1.09 0.59 J/L). While mean VT was not statistically different between modes, in 40% of patients, VT markedly exceeded the lung-protective ventilation target during PRVC and PCV. CONCLUSIONS: During lung-protective ventilation, PCV and PRVC offer no advantage in reducing WOB, compared to VCV with a high flow rate, and in some patients did not allow control of VT to be as precise.