title: Effect of heat and moisture exchanger (HME) positioning on inspiratory gas humidification.
abstract: BACKGROUND
  In mechanically ventilated patients, we investigated how positioning the heat and moisture exchanger (HME) at different places on the ventilator circuit affected inspiratory gas humidification.
  
  
  METHODS
  Absolute humidity (AH) and temperature (TEMP) at the proximal end of endotracheal tube (ETT) were measured in ten mechanically ventilated patients. The HME was connected either directly proximal to the ETT (Site 1) or at before the circuit Y-piece (Site 2: distance from proximal end of ETT and Site 2 was about 19 cm) (Figure. 1). Two devices, Hygrobac S (Mallinckrodt Dar, Mirandola, Italy) and Thermovent HEPA (Smiths Medical International Ltd., Kent, UK) were tested. AH and TEMP were measured with a hygrometer (Moiscope, MERA Co., Ltd., Tokyo, Japan).
  
  
  RESULTS
  Hygrobac S provided significantly higher AH and TEMP at both sites than Thermovent HEPA. Both Hygrobac S and with Thermovent HEPA provided significantly higher AH and TEMP when placed proximally to the ETT.
  
  
  CONCLUSIONS
  Although placement proximal to the ETT improved both AH and TEMP in both HMEs tested, one HME performed better in the distal position than the other HME in the proximal position. We conclude the both the type and placement of HME can make a significant difference in maintaining AH and TEMP during adult ventilation.
authors.affiliation: Department of Emergency and Critical Care Medicine, The University of Tokushima Graduate School, 3-18-15 Kuramoto, Tokushima, 770-8503, Japan. waheihanten@yahoo.co.jp
authors.forename: Daisuke
authors.initials: D
authors.lastname: Inui
authors.forename: Jun
authors.initials: J
authors.lastname: Oto
authors.forename: Masaji
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D000328:Adult; D000368:Aged; D002648:Child; D004867:Equipment Design / Q000295:instrumentation / Q000379:methods; D005260:Female; D006361:Heating / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D006813:Humidity; D001239:Inhalation / Q000502:physiology; D007442:Intubation, Intratracheal / Q000295:instrumentation / Q000379:methods; D008297:Male; D008875:Middle Aged; D012122:Ventilators, Mechanical