title: Hygrometric properties of inspired gas and oral dryness in patients with acute respiratory failure during noninvasive ventilation.
abstract: BACKGROUND
  Because noninvasive ventilation (NIV) delivers medical gas at high flow, inadequate humidification may cause oral dryness and patient discomfort. Heated humidification can be used during NIV, but little has been reported about the effects on the hygrometric conditions inside an oronasal mask and oral dryness during 24 hours on NIV.
  
  
  METHODS
  We measured absolute humidity (AH) inside oronasal masks on subjects with acute respiratory failure during 24 hours on NIV. A single-limb turbine ventilator and oronasal mask with an exhalation port were used for NIV. Oral moistness was evaluated using an oral moisture-checking device, and 3 times during the 24 hours the subjects subjectively scored the feeling of dryness on a 0-10 scale in which 10 was the most severe dryness.
  
  
  RESULTS
  Sixteen subjects were enrolled. The mean ± SD AH inside the mask was 30.0 ± 2.6 mg H2O/L (range 23.1-33.3 mg H2O/L). The median oral moistness was 19.2% (IQR 4.4-24.0%), and the median oral dryness score was 5.5 (IQR 4-7). AH and inspired gas leak correlated inversely, both within the subjects (r = -0.56, P < .001) and between the subjects (r = -0.58, P = .02). AH and oral moistness correlated within the subjects (r = 0.39, P = .04). Oral breathing was associated with reduced oral moistness (P = .001) and increased oral dryness score (P = .002).
  
  
  CONCLUSIONS
  AH varied among the subjects, and some complained of oral dryness even with heated humidifier. Oral breathing decreased oral moistness and worsened the feeling of dryness.
authors.affiliation: Department of Emergency and Critical Care Medicine, University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Oto
authors.forename: Emiko
authors.initials: E
authors.lastname: Nakataki
authors.forename: Nao
authors.initials: N
authors.lastname: Okuda
authors.forename: Mutsuo
authors.initials: M
authors.lastname: Onodera
authors.forename: Hideaki
authors.initials: H
authors.lastname: Imanaka
authors.forename: Masaji
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D000208:Acute Disease; D000368:Aged; D045422:Continuous Positive Airway Pressure / Q000009:adverse effects*; D005260:Female; D005740:Gases / Q000009:adverse effects; D006801:Humans; D006813:Humidity; D008297:Male; D008397:Masks; D008875:Middle Aged; D063087:Noninvasive Ventilation / Q000009:adverse effects*; D012131:Respiratory Insufficiency / Q000628:therapy; D013227:Steam; D014987:Xerostomia / Q000209:etiology*
chemical_list: D005740:Gases; D013227:Steam
keywords: absolute humidity; acute respiratory failure; heated humidifier; noninvasive ventilation; oral dryness