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RESEARCH PRODUCT

Heated breathing tubes affect humidity output of circle absorber systems.

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Abstract Study Objective: To verify whether the airway climate in circle systems can be improved with heated breathing tubes. Design: Randomized, controlled, prospective clinical study. Setting: Operating theater of the Department of Maxillofacial Surgery. Patients: 26 adult patients undergoing prolonged anesthesia. Interventions: A total of 26 prolonged anesthetics were conducted in adult patients using a minimal fresh gas flow rate (0.6 L/min) and silicon breathing tubes (16 mm internal diameter) containing a heated coil. Group 1 ( n = 10 patients) was the control group; breathing tubes were unheated. In Group 2 ( n = 10 patients), breathing tubes were heated to 30°C. In Group 3 ( n = 6 patients), breathing tubes were heated to 36°C. Measurements and Main Results: Humidity and temperature were measured at the Y-piece. Inspiratory temperature in Group 2 was significantly higher than in Group 1. In Group 3, both inspiratory temperature and absolute humidity were significantly higher than in Group 1. After 5 minutes of ventilation, water content and temperature of inspiratory gases were significantly higher in Group 3 than in Group 1. Conclusion: Low flow systems need at least 120 minutes to achieve a satisfactory airway climate. Heated breathing tubes effectively reduce this delay.