A new valveless all-purpose ventilator. Clinical evaluation.

Preliminary clinical evaluation of a new ventilator, which embodies a new valveless design principle and a circuit which is open to atmosphere, has been performed on adult patients undergoing surgery. Using normal respiratory fresh gas flows (100 ml kg-1 min-1) PaCO2 and PaO2 were the same as with a conventional ventilator. High frequency ventilation (HFV) up to 100 b.p.m. caused no statistically significant changes in PaCO2 and PaO2. The peak airway pressures were 30% less than with a Manley ventilator and decreased by a further 40% during HFV, PEEP, NEEP, CPAP and IMV were easily applied.