High-frequency oscillatory ventilation for adult respiratory distress syndrome-A pilot study

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Objective To evaluate the safety and effectiveness of high-frequency oscillatory ventilation using a protocol designed to recruit and maintain optimal lung volume in patients with severe adult respiratory distress syndrome (ARDS).Setting Surgical and medical intensive care units in a tertiary care, military teaching hospital.Design A prospective, clinical study.Patients Seventeen patients, 17 yrs to 83 yrs of age, with severe ARDS (Lung injury Score of 3.81 +/- 0.23) failing inverse ratio mechanical conventional ventilation (PaO2/FIO2 ratio of 68.6 +/- 21.6, peak inspiratory pressure of 54.3 +/- 12.7 cm H2 O, positive end-expiratory pressure of 18.2 +/- 6.9 cm H2 O).Interventions High-frequency oscillatory ventilation was instituted after varying periods of conventional ventilation (5.12 +/- 4.3 days). We employed a lung volume recruitment strategy that consisted of incremental increases in mean airway pressure to achieve a PaO2 of >or=to60 torr (>or=to8.0 kPa), with an FIO2 of Measurements and Main Results High-frequency oscillator ventilator settings (FIO2, mean airway pressure, pressure amplitude of oscillation [Delta P] frequency) and hemodynamic parameters (cardiac output, oxygen delivery [DO2]), mean systemic and pulmonary arterial pressures, and the oxygenation index (oxygenation index = [FIO2 x mean airway pressure x 100]/PaO2) were monitored during the transition to high-frequency oscillatory ventilation and throughout the course of the high-frequency protocol. Thirteen patients demonstrated improved gas exchange and an overall improvement in PaO2/FIO2 ratio (p < .02). Reductions in the oxygenation index (p < .01) and FIO2 (p < .02) at 12, 24, and 48 hrs after starting high-frequency oscillatory ventilation were observed. No significant compromise in cardiac output or DO2 was observed, despite a significant increase in mean airway pressure (31.2 +/- 10.3 to 34.0 +/- 6.7 cm H2 O, p < .05) on high-frequency oscillatory ventilation. The overall survival rate at 30 days was 47%. A greater number of pretreatment days on conventional ventilation (p < .009) and an entry oxygenation index of >47 (sensitivity 100%, specificity 100%) were associated with mortality.Conclusions High-frequency oscillatory ventilation is both safe and effective in adult patients with severe ARDS failing conventional ventilation. A lung volume recruitment strategy during high-frequency oscillatory ventilation produced improved gas exchange without a compromise in DO2. These results are encouraging and support the need for a prospective, randomized trial of algorithm-controlled conventional ventilation vs. high-frequency oscillatory ventilation for adults with severe ARDS. (Crit Care Med 1997; 25:937-947)

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