title: Double-heater-wire circuits and heat-and-moisture exchangers and the risk of ventilator-associated pneumonia.
abstract: OBJECTIVE
  To compare the incidence of ventilator-associated pneumonia (VAP) in patients ventilated in intensive care by means of circuits humidified with a hygroscopic heat-and-moisture exchanger with a bacterial viral filter (HME) or hot-water humidification with a heater wire in both inspiratory and expiratory circuit limbs (DHW) or the inspiratory limb only (SHW).
  
  
  METHODS
  A prospective, randomized trial.
  
  
  METHODS
  A metropolitan teaching hospital's general intensive care unit.
  
  
  METHODS
  Three hundred eighty-one patients requiring a minimum period of mechanical ventilation of 48 hrs.
  
  
  METHODS
  Patients were randomized to humidification with use of an HME (n=190), SHW (n=94), or DHW (n=97).
  
  
  RESULTS
  Study end points were VAP diagnosed on the basis of Clinical Pulmonary Infection Score (CPIS) (), HME resistance after 24 hrs of use, endotracheal tube resistance, and HME use per patient. VAP occurred with similar frequency in all groups (13%, HME; 14%, DHW; 10%, SHW; p=0.61) and was predicted only by current smoking (adjusted odds ratio [AOR], 2.1; 95% confidence interval [CI], 1.1-3.9; p=.03) and ventilation days (AOR, 1.05; 95% CI, 1.0-1.2; p=.001); VAP was less likely for patients with an admission diagnosis of pneumonia (AOR, 0.40; 95% CI, 0.4-0.2; p=.04). HME resistance after 24 hrs of use measured at a gas flow of 50 L/min was 0.9 cm H2O (0.4-2.9). Endotracheal tube resistance was similar for all three groups (16-19 cm H2O min/L; p=.2), as were suction frequency, secretion thickness, and blood on suctioning (p=.32, p=.06, and p=.34, respectively). The HME use per patient per day was 1.13.
  
  
  CONCLUSIONS
  Humidification technique does not influence either VAP incidence or secretion characteristics, but HMEs may have air-flow resistance higher than manufacturer specifications after 24 hrs of use.
authors.affiliation: Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Brisbane, Australia, and Department of Public Health, Manchester University, United Kingdom.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Boots
authors.forename: Narelle
authors.initials: N
authors.lastname: George
authors.forename: Joan L
authors.initials: JL
authors.lastname: Faoagali
authors.forename: John
authors.initials: J
authors.lastname: Druery
authors.forename: Kevin
authors.initials: K
authors.lastname: Dean
authors.forename: Richard F
authors.initials: RF
authors.lastname: Heller
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D003428:Cross Infection / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D004867:Equipment Design; D005260:Female; D005374:Filtration; D006361:Heating / Q000295:instrumentation; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D011015:Pneumonia, Aspiration / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000295:instrumentation*; D018709:Statistics, Nonparametric; D016019:Survival Analysis