Erschienen in:
01.07.2006 | Original
Under-humidification and over-humidification during moderate induced
hypothermia with usual devices
verfasst von:
François Lellouche, Siham Qader, Solenne Taille, Aissam Lyazidi, Laurent Brochard
Erschienen in:
Intensive Care Medicine
|
Ausgabe 7/2006
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Abstract
Objective
In mechanically ventilated patients with induced hypothermia, the
efficacy of heat and moisture exchangers and heated humidifiers to
adequately humidify the airway is poorly known. The aim of the study was to
assess the efficacy of different humidification devices during moderate
hypothermia.
Design
Prospective, cross-over randomized study.
Settings
Medical Intensive
Care Unit in a University Hospital.
Patients and participants
Nine adult patients hospitalized after
cardiac arrest in whom moderate hypothermia was induced (33°C for 24 h).
Interventions
Patients were ventilated at admission (period designated “normothermia”)
with a heat and moisture exchanger, and were randomly ventilated during
hypothermia with a heat and moisture exchanger, a heated humidifier, and an
active heat and moisture exchanger.
Measurements and results
Core temperature, inspired and expired
gas absolute and relative humidity were measured. Each system demonstrated
limitations in its ability to humidify gases in the specific situation of
hypothermia. Performances of heat and moisture exchangers were closely
correlated to core temperature (r
2 = 0.84). During hypothermia, heat and
moisture exchangers led to major under-humidification, with absolute
humidity below 25 mgH2O/l. The active heat and moisture exchanger
slightly improved humidification. Heated humidifiers were mostly adequate
but led to over-humidification in some patients, with inspiratory absolute
humidity higher than maximal water content at 33°C with a positive
balance between inspiratory and expiratory water content.
Conclusions
These results suggest that in the case of moderate hypothermia, heat and moisture
exchangers should be used cautiously and that heated humidifiers may lead to
over-humidification with the currently recommended settings.