Efficiency and safety of mechanical ventilation with a heat and moisture exchanger changed only once a week

The cost of mechanical ventilation (MV) is high. Efforts to reduce this cos t, as long as they are not detrimental for the patients, are needed. MV wit h heat and moisture exchangers (HME) changed every 48 h is safe, efficient, and cost-effective. Preliminary reports suggest that the life span of thes e filters may be prolonged. We determined prospectively whether a hygroscop ic and hydrophobic HME (Hygrobac-Dar; Mallinckrodt) provided safe and effic ient heating and humidification of the inspired gases when changed only onc e a week. Patients who were considered to require mechanical ventilation fo r more than 48 h were included in the study. HMEs were initially set for 7 d. Efficient airway heating and humidification were assessed by clinical pa rameters (number of tracheal suctionings and instillations required, peak a irway pressures) and hygrometric measurements performed by psychrometry. Re sistance was measured from Day 0 to Day 7. Bacterial colonization of circui ts and HMEs was studied. A total of 377 days of mechanical ventilation with 60 HMEs was studied. Clinical parameters and hygrometric measurements did not change between Day 0 and Day 7. Mean absolute humidity was 30.3 +/- 1.3 mg H2O/L on Day 0 and 30.8 +/- 1.5 mg H2O/L on Day 7 (p = 0.7). Endotrache al tube occlusion never occurred. Three HMEs were replaced prematurely beca use of insufficient absolute humidity. This rare event occurred only in pat ients with COPD and after the third day of use. In addition, the absolute h umidity delivered by the HMEs was significantly lower in patients with COPD than in the rest of the population. Resistance did not change from Day 0 t o Day 7 (2.4 +/- 0.3 versus 2.7 +/- 0.3 cm H2O/L/s; p = 0.4). Bacterial sam ples of both circuits and ventilator sides of HMEs were sterile in most cas es. We conclude that mechanical ventilation can be safely conducted in non- COPD patients using an HME changed only once a week, leading to substantial cost savings (about $110,000 per year if these findings were applied to th e university-affiliate hospitals in Paris).