Ventilatory strategy in catastrophic lung disease. Inversed ratio ventilation (IRV) and combined high frequency ventilation (CHFV).

In 105 patients with well-defined catastrophic lung disease, in whom conventional settings were unable to maintain life-sustaining gas exchange, the ventilatory strategy was changed from volume-controlled ventilation with an inspiratory-expiratory ratio (I:E) of 1:2 and PEEP of 15-20 cm H2O to pressure-controlled inverse ratio ventilation with an I:E of 2:1, 3:1 or 4:1 and a set PEEP of 4-8 cm H2O. All patients were ventilated on a Servo 900 B or C ventilator, the primary goal being to decrease the FIO2 below 0.6 and the peak pressure to below 50 cm H2O, while maintaining a PaO2 of 8.00 kPa and a PaCO2 within 10% of the upper limit of normal. In 67 patients the intervention was successful and peak pressure could be reduced to a median of 44 cm H2O (range 37-50). FIO2 could be reduced to a median of 0.50 (range 0.40-0.60). The auto-PEEP effect of IRV increased to a median of 12 cm H2O (range 7-22). No consistent pattern of change in cardiac output was observed. Sixty patients survived more than 3 weeks and 48 were discharged from hospital. The 38 IRV "failures" were changed to pressure-controlled ventilation with superimposed high frequency ventilation (CHFV). In 30 cases the FIO2 could be reduced to a median of 0.60 (range 0.50-0.60) and peak pressures to a median of 50 cm H2O (range 45-60). In 21 patients the PaCO2 increased. Auto-PEEP with CHFV had a median value of 15 cm H2O (range 10-25).(ABSTRACT TRUNCATED AT 250 WORDS)