Open Access Research

In vitro and in vivo evaluation of a new active heat moisture exchanger

Davide Chiumello1*, Paolo Pelosi2, Gilbert Park3, Andrea Candiani4, Nicola Bottino1, Ezio Storelli1, Paolo Severgnini2, Dunia D'Onofrio2, Luciano Gattinoni1 and Massimo Chiaranda2

Author Affiliations

1 Institute of Anesthesia and Critical Care, University of Milan, Policlinico Hospital, IRCCS, Milan, Italy

2 Department of Clinical Science, University of Insubria, Circolo and Fondazione Macchi Hospital, Varese, Italy

3 Department of Intensive Care Research, Addenbrooke's Hospital, Cambridge, United Kingdom

4 Institute of Anesthesia and Critical Care, University of Brescia, Civili Hospital, Brescia, Italy

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Critical Care 2004, 8:R281-R288  doi:10.1186/cc2904

Published: 28 June 2004

Abstract

Introduction

In order to improve the efficiency of heat moisture exchangers (HMEs), new hybrid humidifiers (active HMEs) that add water and heat to HMEs have been developed. In this study we evaluated the efficiency, both in vitro and in vivo, of a new active HME (the Performer; StarMed, Mirandola, Italy) as compared with that of existing HMEs (Hygroster and Hygrobac; Mallinckrodt, Mirandola, Italy).

Methods

We tested the efficiency by measuring the temperature and absolute humidity (AH) in vitro using a test lung ventilated at three levels of minute ventilation (5, 10 and 15 l/min) and at two tidal volumes (0.5 and 1 l), and in vivo in 42 patients with acute lung injury (arterial oxygen tension/fractional inspired oxygen ratio 283 ± 72 mmHg). We also evaluated the efficiency in vivo after 12 hours.

Results

In vitro, passive Performer and Hygrobac had higher airway temperature and AH (29.2 ± 0.7°C and 29.2 ± 0.5°C, [P < 0.05]; AH: 28.9 ± 1.6 mgH2O/l and 28.1 ± 0.8 mgH2O/l, [P < 0.05]) than did Hygroster (airway temperature: 28.1 ± 0.3°C [P < 0.05]; AH: 27 ± 1.2 mgH2O/l [P < 0.05]). Both devices suffered a loss of efficiency at the highest minute ventilation and tidal volume, and at the lowest minute ventilation. Active Performer had higher airway temperature and AH (31.9 ± 0.3°C and 34.3 ± 0.6 mgH2O/l; [P < 0.05]) than did Hygrobac and Hygroster, and was not influenced by minute ventilation or tidal volume. In vivo, the efficiency of passive Performer was similar to that of Hygrobac but better than Hygroster, whereas Active Performer was better than both. The active Performer exhibited good efficiency when used for up to 12 hours in vivo.

Conclusion

This study showed that active Performer may provide adequate conditioning of inspired gases, both as a passive and as an active device.

Keywords:
absolute humidity; airflow resistance; heat moisture exchanger; hot water humidifiers; relative humidity