The effect of a heat and moisture exchanger on humidity in a low‐flow anaesthesia system

• Published in: Anaesthesia Vol. 52; no. 2; pp. 144 - 149
• Main Authors: Henriksson, B.‐Å., Sundling, J., Hellman, A.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Science Ltd 01.02.1997; Blackwell
• Subjects: Abdomen - surgery; Adult; Aged; Aged, 80 and over; Anesthesia; Anesthesia, Closed-Circuit - instrumentation; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Anesthesia: equipment, devices; Biological and medical sciences; breathing systems; Female; Gases - administration & dosage; heat and moisture exchanger; Hot Temperature; Humans; Humidifications. Equipment; Humidity; low flow; Male; Medical sciences; Middle Aged; Temperature; Flow rate; Low; Heat exchanger; Humidifier; General anesthesia; Apparatus; Anesthetic circuit; Inhalation
• ISSN: 0003-2409; 1365-2044
• DOI: 10.1111/j.1365-2044.1997.17-az018.x

The heat and humidity in a low‐flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 2 l.min−1) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (5 l.min−1) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 5 l.min−1 fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. Thirty minutes after the start of anaesthesia a control measurement was performed, after which a heat and moisture exchanger was inserted into the breathing system of the three groups randomly allocated to have one. Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low‐flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l−1) but at a fresh gas flow of 5 l.min−1 there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.