• M Chiaranda, L Verona, O Pinamonti, L Dominioni, G Minoja, and G Conti.
• Department of Surgery, Anaesthesiology and Intensive Care, University of Pavia, Varese, Italy.
• Intensive Care Med. 1993 Jan 1; 19 (8): 462-6.

ObjectiveTo investigate the flow-resistance of a new generation of Heat Moisture Exchanging Filters (HME filters) during 24 h of clinical use.DesignBefore-after trial.SettingA general Intensive Care Unit of a university hospital.PatientsA consecutive series of 96 patients undergoing mechanical ventilation for respiratory insufficiency of various etiology and severity.MethodsThe characteristics of the secretions collected by tracheal suctioning and the pressure/flow relationship of the HMEs before and after 24 h of clinical use were analyzed.ResultsThe resistance of the HMEs when dry was 2 hPa/l.s, and it increased to a maximum of 1 hPa/l.s in 83% of the patients after 24 hours; in four patients with particularly heavy secretions HME resistance was 4-5 hPa/l.s. There were no significant modifications of the secretions within the investigation period, excluding, in particular, an increase in density with consequent tracheal tube obstruction.ConclusionThe gas conditioning efficiency and design performance of the tested HMEs did not create a significant obstacle to airflow medium term mechanical ventilation; however, these devices should be cautiously used in patients with heavy bronchial secretions.

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