title: Short-term effects of humidification devices on respiratory pattern and arterial blood gases during noninvasive ventilation.
abstract: BACKGROUND
  The impact of humidification devices on ventilatory and arterial blood gases parameters during noninvasive ventilation (NIV) remains controversial. The aim of the study was to compare the short-term impact of heat and moisture exchangers (HMEs) and heated humidifiers (HHs)  during NIV for either hypercapnic or hypoxemic acute respiratory failure.
  
  
  METHODS
  Consecutive subjects receiving NIV were successively treated with HME and HH in randomized order for 30 min each. At the end of each period, arterial blood gases were measured and ventilatory parameters were  recorded.
  
  
  RESULTS
  Eighty-one subjects were enrolled, of whom 52 were hypercapnic (with or without acidosis) and 29 hypoxemic. Minute ventilation was greater with the HME, in comparison with the HH (15 [12-18] vs 12 [10-16] median [interquartile range], P < .001), while  P(aCO(2)) was increased when using HME, indicating a dead space effect. This effect was observed in all subjects, but was more pronounced in hypercapnic subjects (P(aCO(2)) 62 ± 17 mm Hg with HME vs 57 ± 14 with HH, P < .001). In  a subgroup of 19 subjects with respiratory acidosis, alveolar hypoventilation improved only with the HH. The amplitude of the dead space impact was a function of the degree of hypercapnia.
  
  
  CONCLUSIONS
  Use of an HME decreased CO(2) elimination during NIV, despite increased minute  ventilation, especially in hypercapnic subjects.
authors.affiliation: Service de Réanimation Médicale, Assistance Publique Hôpitaux de Paris, Centre Hospitalier Albert Chenevier-Henri Mondor, Créteil, France. francois.lellouche@criucpq.ulaval.ca
authors.forename: François
authors.initials: F
authors.lastname: Lellouche
authors.forename: Claudia
authors.initials: C
authors.lastname: Pignataro
authors.forename: Salvatore Maurizio
authors.initials: SM
authors.lastname: Maggiore
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Girou
authors.forename: Nicolas
authors.initials: N
authors.lastname: Deye
authors.forename: Solenne
authors.initials: S
authors.lastname: Taillé
authors.forename: Marc
authors.initials: M
authors.lastname: Fischler
authors.forename: Laurent
authors.initials: L
authors.lastname: Brochard
mesh_terms: D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000378:metabolism; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000628:therapy*; D012121:Respiration, Artificial / Q000295:instrumentation*; D012126:Respiratory Dead Space; D012129:Respiratory Function Tests; D018709:Statistics, Nonparametric; D016896:Treatment Outcome
chemical_list: D002245:Carbon Dioxide