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 premix 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.

Critical orifice and expiratory volume, Indicator gas, Mechanical ventilation, Wash-out test
dx.doi.org/10.1007/BF01706480, hdl.handle.net/1765/67070
Intensive Care Medicine
Department of Surgery

Gultuna, I, Huygen, P.E.M, Jabaaij, C, Holland, W.P, Ince, C, & Bruining, H.A. (1992). A simple device to inject indicator gas for wash-out tests during mechanical ventilation. Intensive Care Medicine, 18(5), 304–308. doi:10.1007/BF01706480