Bedside evaluation of efficient airway humidification during mechanical ventilation of the critically ill

Chest. 1999 Jun;115(6):1646-52. doi: 10.1378/chest.115.6.1646.


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.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Acute Disease
  • Body Temperature
  • Critical Illness
  • Hot Temperature
  • Humans
  • Humidity*
  • Intensive Care Units
  • Intubation, Intratracheal
  • Middle Aged
  • Observer Variation
  • Point-of-Care Systems*
  • Prospective Studies
  • Respiration, Artificial / methods*
  • Respiration, Artificial / standards
  • Respiratory Insufficiency / therapy*
  • Trachea / physiology