Carbon dioxide retention associated with a humidifier defect.

A case is presented which describes a patient who developed hypercarbia resulting from a defective humidifier. A Puritan-Bennett Cascade I humidifier was incorporated into a circle system between the inspiratory dome one way valve and the patient. A screw which supports the thermal well to the head of the humidifier was missing, thereby allowing an intermittent leak to develop in the system. The leak was present when the system pressure dropped to ambient level; however, at positive system pressure the leak sealed. This allowed exhaled gases into the inspiratory limb of the circuit unchecked by the inspiratory valve yet when the breathing circuit was occluded at the patient end and submitted to pressures of 20 and 40 cm H2O, no leaks were detected. Intraoperatively, PaCO2 was noted to be as high as 68 mmHg just prior to removing the humidifier from the circuit and corrected to 38 mmHg within 15 minutes of removal of the humidifier.