Study objective: To determine the correlation between
simple rating of condensation seen in the flex-tube connecting the
heating and humidifying device used with the endotracheal tube and
hygrometric parameters (absolute and relative humidity and tracheal
temperature) measured by psychrometry.
Prospective randomized clinical trial.
Medical ICU of Louis Mourier Hospital, Colombes, France, a
university-affiliated teaching hospital.
Forty-five consecutive mechanically ventilated critically ill
Interventions: Patients undergoing
mechanical ventilation were randomly assigned to receive humidification
with one of the four heat and moisture exchangers (HMEs) tested or with
a conventional heated humidifier.
hygrometric performances of four HMEs (BB2215, BB50, and BB100 from
Pall Biomedical, Saint-Germaine-en-Laye, France; and Hygrobac-Dar from
Mallinckrodt, Mirandola, Italy) and a heated humidifier (Fisher &
Paykel; Auckland, New Zealand) were studied after 3 h and also
after 48 h of use for the Hygrobac-Dar and correlated to a
clinical visual inspection rating the amount of condensation in the
flex-tube of the endotracheal tube.
Results: A total
of 95 measurements in 45 patients were performed. The best hygrometric
parameters were obtained with the heated humidifier (p < 0.001). The
Hygrobac-Dar yielded significantly higher values for both humidities
and tracheal temperature than the other three HMEs (p < 0.001). The
performance of Hygrobac-Dar was unchanged after 48 h of use. There
was a significant correlation between the condensation seen in the
flex-tube and the hygrometric parameters measured by psychrometry
(absolute humidity, rho = 0.7; relative humidity, rho = 0.7;
tracheal temperature, rho = 0.5, p < 0.0001).
Conclusion: In mechanically ventilated ICU patients, visual
evaluation of the condensation in the flex-tube provides an estimation
of the heating and humidifying efficacy of the heating and humidifying
device used, thus allowing the clinician bedside monitoring of airway