title: Safety, efficacy, and cost-effectiveness of mechanical ventilation with humidifying filters changed every 48 hours: a prospective, randomized study.
abstract: OBJECTIVE
  To determine whether three hydrophobic and hygroscopic heat and moisture exchangers (HMEs) retain their heating and humidifying properties (assessed by psychrometric measurements of absolute humidity, relative humidity, and tracheal temperature) for 48 hrs without any drop in their bacteriologic efficiency.
  
  
  METHODS
  Prospective randomized clinical trial.
  
  
  METHODS
  Sixty-one consecutive unselected mechanically ventilated intensive care unit patients.
  
  
  METHODS
  Patients were randomly allocated to one of the three HMEs studied (Hygrobac-Dar from Mallinckrodt, n = 21; Humid-Vent from Gibeck, n = 20; and Clear-Thermal from Intersurgical, n = 20).
  
  
  RESULTS
  Hygrometric parameters were measured by psychrometry after 3, 24, and 48 hrs of use. Peak airway pressure was recorded every 6 hrs and averaged over 24 hrs. Bacterial colonization of both patients and circuits was studied. Patients in all three groups were similar in terms of age, indications for, and overall duration of mechanical ventilation. Tracheal tube occlusion never occurred. Hygrometric data included 371 measurements whereas bacteriologic data included >700 samples and cultures. The Hygrobac-Dar HMEs gave a significantly higher absolute humidity whatever the time of measurement (3, 24, or 48 hrs) than the other two HMEs (p < .001). The Clear-Thermal HMEs gave the poorest hygrometric parameters (p < .01); five of them were replaced prematurely (24 hrs) because the absolute humidity was <25 mg H2O/L. This did not occur for the other HMEs. Mean peak airway pressures were identical in the three groups. The bacterial colonizations of both patient and circuit were similar (and negligible for circuits) for all three groups.
  
  
  CONCLUSIONS
  Some HMEs may be used safely for 48 hrs without change. However, this does not pertain to every brand of HME. Objective in vivo evaluation of their humidifying performances is decisive before extending their duration of use.
authors.affiliation: Service de Réanimation Médicale, Hôpital Louis Mourier, Faculté Xavier Bichat, Université Paris VII, France.
authors.forename: P
authors.initials: P
authors.lastname: Markowicz
authors.forename: J D
authors.initials: JD
authors.lastname: Ricard
authors.forename: D
authors.initials: D
authors.lastname: Dreyfuss
authors.forename: L
authors.initials: L
authors.lastname: Mier
authors.forename: P
authors.initials: P
authors.lastname: Brun
authors.forename: F
authors.initials: F
authors.lastname: Coste
authors.forename: Y
authors.initials: Y
authors.lastname: Boussougant
authors.forename: K
authors.initials: K
authors.lastname: Djedaïni
mesh_terms: D000208:Acute Disease; D000704:Analysis of Variance; D015169:Colony Count, Microbial; D003362:Cost-Benefit Analysis; D004869:Equipment Safety; D005260:Female; D005374:Filtration; D006801:Humans; D006813:Humidity; D008173:Lung Diseases, Obstructive / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000191:economics / Q000295:instrumentation*; D012131:Respiratory Insufficiency / Q000628:therapy; D013673:Technology Assessment, Biomedical; D013997:Time Factors; D017155:Wettability