[Clinical study of imposed work of breathing caused by the breathing apparatus].

OBJECTIVE: The imposed work of breathing caused by the breathing apparatus (endotracheal tube, breathing circuit tubing, and ventilator's valves) may increase patient's work of breathing. To evaluate the imposed work may be useful to determine weaning. METHODS: Work of breathing was observed by Bicore CP-100 breathing monitor at different levels pressure support (PS), T piece and after extubation, and the PS level to compensate imposed work of breathing was computed. RESULTS: When PS level decreased, patient's work of breathing increased significantly. At PS O kPa, the patient's work of breathing increased 57%, which was caused by imposed work of apparatus. Because of the resistance of endotracheal tube, the patient's work of breathing increased 41% at T piece. The PS level that compensated for the imposed work was 0.7 kPa. CONCLUSIONS: When PS level was too low or T piece was applied, the imposed work of breathing caused by apparatus could markedly increase patient's work of breathing.