Gas temperatures and humidities were examined when the fresh gas flow into a circle absorber system was one 1/minute. The environment cooled gases in the circuit to a minimum at the patient end of the inspiratory tubing; here the saturated gas was 2°C above room temperature. Moisture uptake kept pace with temperature gain during inspiration and relative humidities remained high. Under these conditions, heat and moisture exchange in the artificial airways produced end-inspired temperatures and humidities in the gases entering the trachea which were close to normal subglottic values.
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