title: Clinical factors affecting inspired gas humidification and oral dryness during noninvasive ventilation.
abstract: OBJECTIVE
  Oral dryness is a common complication during noninvasive ventilation (NIV). We measured the oral dryness of patients and performed a bench study to investigate factors related to humidification during NIV.
  
  
  METHODS
  Patients were randomly assigned into 2 groups: medium (Med group) and maximum (Max group) heated humidifier (HH) settings. Oral moistness was measured using an oral moisture-checking device, and the feeling of oral dryness was evaluated using a 0 to 10 numerical rating scale (NRS) at 0, 12, and 24 hours from the beginning of NIV and at 12 and 24 hours after NIV was discontinued. A bench study was performed to assess the effects of positive end-expiratory pressure (PEEP), the fraction of inspired oxygen (F(I)O(2)), and air leaks on absolute humidity. We evaluated 3 HH settings: no HH, HH at the medium setting, and HH at the maximum setting. The temperature in the outlet chamber was 31°C to 32°C for the medium HH setting and 38°C to 41°C for the maximum HH setting.
  
  
  RESULTS
  In the clinical study, 12 patients were assigned to the Med group and 11 to the Max group. In the Med group, oral moistness decreased and NRS increased at 12 and 24 hours compared with 0 hours (P < .05). In the Max group, neither the oral moistness nor the NRS changed throughout the study period, whereas in the bench study, high F(I)O(2), high PEEP, and air leak decreased the absolute humidity for both HH settings (P < .01). However, it is not clear to what extent these factors affected the patients' oral dryness because the ranges of F(I)O(2) and PEEP were narrow.
  
  
  CONCLUSIONS
  Oral dryness was a common problem in our patients. The HH setting significantly affected humidification and oral dryness during NIV.
authors.affiliation: Emergency and Critical Care Medicine, The University of Tokushima Graduate School, Tokushima 770-8503, Japan. Electronic address: joto@clin.med.tokushima-u.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Oto
authors.affiliation: Emergency and Disaster Medicine, The University of Tokushima Graduate School, Tokushima 770-8503, Japan. Electronic address: imanakah@clin.med.tokushima-u.ac.jp.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Imanaka
authors.affiliation: Emergency and Critical Care Medicine, The University of Tokushima Graduate School, Tokushima 770-8503, Japan. Electronic address: nmasaji@clin.med.tokushima-u.ac.jp.
authors.forename: Masaji
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003422:Critical Care; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000009:adverse effects*; D013997:Time Factors; D014987:Xerostomia / Q000209:etiology*