title: Effect of the humidification device on the work of breathing during noninvasive ventilation.
abstract: OBJECTIVE
  Heat and moisture exchangers (HME) increase circuitry deadspace compared to heated humidifiers (HH). This study compared the effect of HH and HME during noninvasive ventilation (NIV) on arterial blood gases and patient's effort assessed by respiratory muscles pressure-time product and by work of breathing (WOB).
  
  
  METHODS
  Randomized cross-over study in a medical intensive care unit.
  
  
  METHODS
  Nine patients receiving NIV for moderate to severe acute hypercapnic respiratory failure.
  
  
  METHODS
  HME was randomly compared to HH during periods of 20 min. Each device was studied without (ZEEP) and with a PEEP of 5 cmH(2)O. At the end of each period arterial blood gases, ventilatory parameters, oesophageal and gastric pressures were recorded and indexes of patient's effort calculated.
  
  
  RESULTS
  Minute ventilation was significantly higher with HME than with HH (ZEEP: 15.8+/-3.7 vs. 12.8+/-3.6 l/min) despite a similar PaCO(2) (60+/-16 vs. 57+/-16 mmHg). HME was associated with a greater increase in WOB (ZEEP: 15.5+/-7.7 vs. 8.4+/-4.5 J/min and PEEP: 11.3+/-5.7 vs. 7.3+/-3.8 J/min) and indexes of patient effort. NIV with HME failed to decrease WOB compared to baseline. Addition of PEEP reduced the level of effort, but similar differences between HME and HH were observed.
  
  
  CONCLUSIONS
  In patients receiving NIV for moderate to severe acute hypercapnic respiratory failure, the use of HME lessens the efficacy of NIV in reducing effort compared to HH.
authors.affiliation: Medical Intensive Care Unit, Hôpital Henri Mondor, AP-HP, Université Paris 12 et INSERM U492, 51 av du Maréchal de Lattre de Tassigny, 94010 Créteil, France.
authors.forename: François
authors.initials: F
authors.lastname: Lellouche
authors.forename: Salvatore M
authors.initials: SM
authors.lastname: Maggiore
authors.forename: Nicolas
authors.initials: N
authors.lastname: Deye
authors.forename: Solenne
authors.initials: S
authors.lastname: Taillé
authors.forename: Jérôme
authors.initials: J
authors.lastname: Pigeot
authors.forename: Alain
authors.initials: A
authors.lastname: Harf
authors.forename: Laurent
authors.initials: L
authors.lastname: Brochard
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001784:Blood Gas Analysis; D018592:Cross-Over Studies; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial / Q000379:methods*; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy*; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D014939:Work of Breathing