RT Journal Article
SR Electronic
T1 Development of a New Method for Evaluating Heat-and-Moisture Exchanger Performance
JF Respiratory Care
FD American Association for Respiratory Care
SP respcare.11696
DO 10.4187/respcare.11696
A1 Nagata, Kouhei
A1 Andoh, Tomio
A1 Kishimoto, Ken
A1 Eguchi, Kunihisa
A1 Usuda, Yutaka
A1 Tsuji, Toshihiro
A1 Hirabayashi, Go
A1 Maruyama, Koichi
YR 2024
UL http://rc.rcjournal.com/content/early/2024/07/09/respcare.11696.abstract
AB BACKGROUND: A model system described in International Organization for Standardization 9360 is the standard method for estimating the humidifying performance of heat-and-moisture exchangers (HMEs). However, there are no reliable bedside methods for evaluating the ongoing humidification performance of HMEs. Therefore, this study aimed to develop 2 clinically applicable methods for estimating the ongoing humidifying performance of HMEs and to evaluate their reliability in a model system.METHODS: Physiologically expired gas was simulated using a heated humidifier, and ventilation was delivered using a ventilator with constant flow through 3 different types of HMEs. Relative humidity (RH) was measured using a capacitive-type moisture sensor. Water content lost during expiration was calculated by integrating absolute humidity (AH), instantaneous gas flow measured at the expiratory outlet of the ventilator, and time. We also calculated the water content released and captured by the HMEs during tidal ventilation by integrating the difference in AH across the HMEs, instantaneous gas flow, and time.RESULTS: We found that the RH, temperature, and AH were almost constant on the expiratory outlet of the ventilator but rapidly varied near the HMEs. The water content lost by the 3 HMEs was associated with the manufacturer-reported values and inversely correlated with the calculated values of the water content exchanged by the HMEs. The water content released and captured by HMEs was closely correlated with the difference in HME weight measured at the end of inspiration and expiration; however, the water content captured by HMEs seemed to be overestimated.CONCLUSIONS: Our results demonstrated that our system was able to detect the differences in the performance of 3 models of HMEs and suggest that our method for calculating water loss is reliable for estimating the water retention performance of HMEs during mechanical ventilation, even in the presence of a constant flow.