We report a case in which an obstructive bronchial cast 3 inches in length was produced during mechanical ventilation despite the use of a Servo SH 150 'artificial nose' type of humidifier. This suggests that use of this device can be inappropriate for patients requiring long-term ventilation. One should consider such variables as minute vol-ume, inspiratory flowrates, and degree of secretion production before deciding to employ this kind of humidifier.
Perch et al. (Mon,) studied this question.