In vitro and in vivo evaluation of a new active heat moisture exchanger.
BACKGROUND
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 degrees C and 29.2 +/- 0.5 degrees 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 degrees 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 degrees 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.


CONCLUSIONS
This study showed that active Performer may provide adequate conditioning of inspired gases, both as a passive and as an active device.
Institute of Anesthesia and Critical Care, University of Milan, Policlinico Hospital, IRCCS, Milan, Italy. chiumello@libero.it
Davide
D
Chiumello
Paolo
P
Pelosi
Gilbert
G
Park
Andrea
A
Candiani
Nicola
N
Bottino
Ezio
E
Storelli
Paolo
P
Severgnini
Dunia
D
D'Onofrio
Luciano
L
Gattinoni
Massimo
M
Chiaranda
D000208:Acute Disease; D004526:Efficiency; D004867:Equipment Design; D005374:Filtration / Q000295:instrumentation; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D066298:In Vitro Techniques; D008168:Lung / Q000502:physiology; D055370:Lung Injury; D012123:Pulmonary Ventilation / Q000502:physiology*; D012121:Respiration, Artificial / Q000295:instrumentation* / Q000379:methods; D020545:Respiratory Mucosa; D013673:Technology Assessment, Biomedical; D013990:Tidal Volume; D012122:Ventilators, Mechanical