Preservation of humidity and heat of respiratory gases in spontaneously breathing, tracheostomized patients

Background: Ventilation with endotracheal intubation bypasses the upper airway and the normal heat and moisture exchanging process of inspired gases. A continuous loss of moisture and heat occurs and predisposes patients to serious airway damage. We therefore prospectively studied one heated humidifier system, one cold humidifier system and one heat and moisture exchanger in spontaneously breathing, tracheostomized intensive care unit patients to determine the ability to preserve patients' heat and water. Methods: Following a randomized order, 10 patients were spontaneously ventilated for 24-h periods with the Nam 35(R) humidifier (Europe Medical, France, a cold water humidifier), the heat and moisture exchanger Trach-Vent(R) (Gibeck, Sweden), and the Aerodyne(R) humidifer (Kendall, USA). in each patient, during the inspiration phase, the following measurements were performed: mean values of temperature and relative humidity of inspired gases. The absolute humidity was calculated. Values were obtained in each patients after 40 min and 24 h. Results: The Trach-Vent(R) filter and the Aerodyne(R) humidifier had better humidification and thermic capacities than the Nam 35(R) humidifier (P<0.001). With the Nam 35(R) humidifier, no patient had temperature of inspired gas >29 degrees C Concerning absolute humidity of inspired gases, the Nam 35(R) humidifier achieved a lower performance than the other two tested systems (P<0.001). Conclusion: In spontaneously breathing, tracheostomized intensive care unit patients, the Trach-Vent(R) heat and moisture exchanger and the Aerodyne(R) heated system achieved satisfactorily preservation of heat and humidity of inspired gases.