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 H eat Moisture Exchanging Filters (HME filters) during 24 h of clinical use. Design: Before-after trial. Setting: A general Intensive Care Uni t of a university hospital. Patients: A consecutive series of 96 patie nts undergoing mechanical ventilation for respiratory insufficiency of various etiology and severity. Methods: The characteristics of the se cretions collected by tracheal suctioning and the pressure/flow relati onship 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 i ncreased to a maximum of 1 hPa/l.s in 83% of the patients after 24 hou rs; in four patients with particularly heavy secretions HME resistance was 4-5 hPa/l.s. There were no significant modifications of the secre tions within the investigation period, excluding, in particular, an in crease in density with consequent tracheal tube obstruction. Conclusio n: The gas conditioning efficiency and design performance of the teste d HMEs did not create a significant obstacle to airflow medium term me chanical ventilation; however, these devices should be cautiously used in patients with heavy bronchial secretions.