Anaesthesia
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Breathing system filters are recommended for use during anaesthesia to protect the patient from inhaling gas-borne particles. Filters placed at the patient connection port of the breathing system can also humidify the inspired gases. ⋯ The moisture content of the end-inspired air at the end of the 3-min period varied from 6.4 to 27.8 and from 4.4 to 25.9 g.m-3 for tidal volumes of 0.5 and 1.0 l, respectively (p < 0.0001 for all pairwise comparisons of the five filters and for the two tidal volumes). Those breathing system filters that have at least an adequate level of performance (at least 20 g.m-3) will generally achieve this level within the 3-min pre-oxygenation period.