A simple device to inject indicator gas for wash-out tests during mechanical ventilation.

Abstract

To evaluate a simple device which injects a constant fraction of indicator gas to the inspiratory mixture for performing multi-breath wash-out tests during controlled ventilation. the technique in which the indicator gas is injected at the mouth of the patient (post-mix) is compared with the technique where the indicator gas is administered in the bellows of the ventilator (pre-mix). Surgical Intensive Care Unit of a University Hospital. 10 post-operative mechanically ventilated patients. None. 3 wash-out tests with the post-mix and 3 wash-out tests with the pre-mix method were performed within an hour on every patient. The calculated mean end expiratory lung volume (EEV) was 1.91 +/- 0.871 with the post-mix technique and 1.89 +/- 0.881 with the pre-mix technique. There was a good agreement with a mean difference of -1.9 +/- 6.5% in the calculated EEV values by the two different techniques. The described injector is an affordable device, is easy to assemble and can be incorporated in most electronically regulated ventilators to perform multi-breath indicator gas wash-out tests for pulmonary monitoring at the bed side of ICU patients.