The performance of a new valveless ventilator at rates of up to 250 bpm.

The efficacy of a new ventilator, incorporating a valveless pneumatic exhalation circuit, at rates of up to 250 bpm was first assessed in the laboratory. Using this ventilator the effect of fast rate ventilation on blood gases of infants with acute respiratory distress was then examined. Infants were studied at three rates: 60, 125 and 250 bpm. Peak inflating and positive end expiratory pressure, inspiratory: expiratory ratio and inspired oxygen were kept constant. The laboratory study demonstrated that as ventilator rate was increased the delivered volume fell, but even at 250 bpm the delivered volume was 7 ml. In the clinical study, oxygenation at 250 bpm was not significantly different from that at 60 bpm, but significantly lower than at 125 pbm. Carbon dioxide levels were significantly lower at 250 bpm that at 60 bpm, but did not differ significantly from that at 125 bpm. We conclude increasing ventilator rate from 125 to 250 bpm is not advantageous for infants ventilated for acute respiratory distress.