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

Abstract

To investigate the flow-resistance of a new generation of Heat Moisture Exchanging Filters (HME filters) during 24 h of clinical use. Before-after trial. A general Intensive Care Unit of a university hospital. A consecutive series of 96 patients undergoing mechanical ventilation for respiratory insufficiency of various etiology and severity. 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. 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. 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.