Alveolar deadspace during high frequency positive pressure ventilation. Influence of ventilatory pattern.

Pulmonary gas exchange was studied in association with high frequency ventilation and its relation to the duration of insufflation and end-expiratory pressure investigated. Alveolar deadspace, alveolar ventilation and the alveolar-arterial oxygen difference were obtained in cats receiving a constant minute ventilation. Alveolar deadspace increased with ventilatory frequency when a long insufflation time was used. A positive end-expiratory pressure (PEEP) decreased the alveolar deadspace in high frequency ventilation. Thus, with the low compressible volume ventilator, more efficient high frequency ventilation can be achieved with a short period of insufflation plus low PEEP.