Use of heat and moisture exchanging (HME) filters in mechanically ventilated ICU patients: influence on airway flow-resistance.

Objective: To investigate the flow-resistance of a new generation of Heat Moisture Exchanging Filters (HME filters) during 24 h of clinical use.

Design: Before-after trial.

Setting: A general Intensive Care Unit of a university hospital.

Patients: A consecutive series of 96 patients undergoing mechanical ventilation for respiratory insufficiency of various etiology and severity.

Methods: The 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.

Results: The 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.

Conclusion: The 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.