A simple device to inject indicator gas for wash-out tests during mechanical ventilation
Intensive Care Med, 18 (5):
304--308 (1992)Abstract
OBJECTIVE: 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. DESIGN: 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). SETTING: Surgical Intensive Care Unit of a University Hospital. PATIENTS: 10 post-operative mechanically ventilated patients. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: 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. CONCLUSION: 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.