HME Passive Humidification — FRCA Primary MCQ
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Correct answer: D — It passively captures expired heat and moisture on a hygroscopic membrane and returns it during inspiration
The HME passively conserves heat and moisture from the patient's exhaled gas on a hygroscopic or hydrophobic element. During inspiration this heat and moisture is returned to the dry inspired gas. It adds approximately 30-90 mL of dead space. It achieves approximately 70-80% humidity efficiency. HME filters combine HME with bacterial/viral filtration.
Reference: Al-Shaikh Stacey 2019 Essentials of Anaesthetic Equipment