rapidly absorbed and complications will readily resolve once insufflation has ceased. Reference

Correspondence markedly than in non-and exsmokers [I], and is dependent on tidal volume [2]. I ventilated the lungs of 58 patients at two settings (firstly at 17 breath.min-l, volume 0.4-0.51, and than at 9 breath.min-l, volume 0.7-0.81), so that group mean Paco, was the same at both settings. At small volumes, median Paco,-PE'co, and the 5th and 95th percentiles were 0.6, 0.2 and 1.4 kPa; at large they were 0.3-0.1 and 1.1 kPa. Mean Paco,-PE'co, was thus 0.3 kPa less at the larger tidal volume; in some young patients Paco2-PE'co2 was small and did not change much with ventilator setting. Pace,-PE'co, was greater in patients with delayed pulmonary emptying, i.e. airways obstruction.The capnograph and pulse oximeter allow excellent monitoring of ventilation. Ventilator systems are bulky enough; the variable deadspace is unnecessary.

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.

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