The Science Journal of the American Association for Respiratory Care

1999 OPEN FORUM Abstracts

AN EVALUATION OF AN ACTIVE HEAT AND MOISTURE EXCHANGER THE HME BOOSTER

J M Anthony* V Knowles MBChB and G R Park MD, DMedSci, FRCA John Farman Intensive Care Unit, Addenbrooke's Hospital, Cambridge England and * Tomtec Vogelkerslaan 20, 2950 Kappellen, Belgium.

Background: In the critically ill or anaesthetised patient adequate humidification is essential if the trachea is intubated for a long time. Under-humidification may result in airway plugging and damage to the airways. Excessive humidification can lead to profuse secretions. Fixed performance humidifiers, such as Heat and Moisture Exchanger (HME) and heated water baths (HWB) take no account of patient variability. We have previously reported an Active HME (aHME)1 and now report an evaluation of the similar commercially available model, the HME booster. This aHME comprises a conventional HME. Between this and the tracheal tube a T piece is fitted. Into the T piece a heated plug is fitted, over the end of which is a GoretexTM membrane. Between the heater and the membrane water is injected. The heater vapourises the water which passes through the membrane. The amount of water vapour passing through the membrane depends on the humidity of the airway gas; regulating the flow of water into the device. Method: A similar method to that used before 1 was used. A ventilator delivering a 20°C, tidal volume 1L, frequency 10 breaths/a min into a test lung at 34°C (1S0 9360) for 12h was used. In the circuit the humidifer as shown in the table was placed and the variables shown measured.

Results:

H2O loss Temperature (°C)
g/h Insp. Exp.
Without HME 8.9 21.3 34
HMEF DAR Hydrobag 5² 4.5 29 34.3
DAR Hygrobag ?S? 2 34.1 35.8
HWB (Fischer Paykel) 3.3 33.2 35.4
with heated hoses, main setting 33°C, Chamber setting -1°C
HWB (Fischer Paykel 2.3 34.8 36.6
with heated hoses, main setting 36°C, Chamber setting -1°C

The aHME reduced water loss from the circuit and had the highest temperatures except for the HWB at its higher setting. Conclusion: This aHME offers adaptable humidification. It can give equivalent humidification to a HWB. The cost of each disposable part for the aHME is £3.29, while the cost of disposables for the HWB is £21. Initial capital costs are aHME £49.50, HWB £1,300. The aHME is cheaper to buy and run and in the laboratory as effective as the HWB. 1. F Kapadia et al Brit J. Anaesth 1992;69,640

OF-99-090

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