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Bedside evaluation of efficient airway humidification during mechanical ventilation of the critically ill
J D Ricard1, P Markowicz, K Djedaini
1Service de Réanimation Médicale, Hôpital Louis Mourier (Assistance Publique-Hopitaux de Paris), Colombes, France.
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.
Design:
Prospective randomized clinical trial.
Setting:
Medical ICU of Louis Mourier Hospital, Colombes, France, a university-affiliated teaching hospital.
Patients:
Forty-five consecutive mechanically ventilated critically ill patients.
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.
Measurements:
The 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 humidification.