title: Safety of combined heat and moisture exchanger filters in long-term mechanical ventilation.
abstract: OBJECTIVE
  To evaluate the safety of a combined heat and moisture exchanger filter (HMEF) for the conditioning of inspired gas in long-term mechanical ventilation (MV).
  
  
  METHODS
  Randomized controlled trial.
  
  
  METHODS
  Medical ICU in a large teaching hospital.
  
  
  METHODS
  One hundred fifteen consecutive patients who required > or = 48 h of MV.
  
  
  METHODS
  Patients were randomized at intubation time (day 1) to receive inspired gas conditioned either by a water-bath humidifier heated at 32 degrees C (HWBH) or by an HMEF (Hygroster; DAR; Mirandola, Italy).
  
  
  RESULTS
  The two study groups were comparable in terms of primary pathologic condition at the time of hospital admission, disease severity as measured by the Simplified Acute Physiology Score, and ICU mortality. They did not differ with respect to ventilator days per patient (mean +/- SD: HMEF, 7.6 +/- 6.5; HWBH, 7.8 +/- 5.8), incidence of endotracheal tube obstruction (HMEF, 0/59; HWBH, 1/56), and incidence of hypothermic episodes (HMEF, five; HWBH, two). In 41 patients receiving MV for > or = 5 days, the morphologic integrity of respiratory epithelium was evaluated on day 1 and day 5, using a cytologic examination of tracheal aspirate smears. The state of ciliated epithelium was scored on a scale from 0 (poorest integrity) to 1,200 (maximum integrity), according to a well-described method. In both patient groups, the scores slightly but significantly decreased from day 1 to day 5 (mean +/- SD: HWBH, from 787 +/- 104 to 745 +/- 88; HMEF, from 813 +/- 79 to 739 +/- 62; p < 0.01 for both groups); there were no statistically significant differences between groups.
  
  
  CONCLUSIONS
  These data indicate acceptable safety of HMEFs of the type used in the present study for long-term mechanical ventilation.
authors.affiliation: Institut de Physiopathologie Clinique, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
authors.forename: J M
authors.initials: JM
authors.lastname: Hurni
authors.forename: F
authors.initials: F
authors.lastname: Feihl
authors.forename: R
authors.initials: R
authors.lastname: Lazor
authors.forename: P
authors.initials: P
authors.lastname: Leuenberger
authors.forename: C
authors.initials: C
authors.lastname: Perret
mesh_terms: D004869:Equipment Safety; D005260:Female; D006801:Humans; D006813:Humidity; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial / Q000009:adverse effects / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D014132:Trachea / Q000473:pathology; D012122:Ventilators, Mechanical