title: Humidification of inspired oxygen is increased with pre-nasal cannula, compared to intranasal cannula.
abstract: BACKGROUND
  Oxygen therapy is usually combined with a humidification device, to prevent mucosal dryness. Depending on the cannula design, oxygen can be administered pre- or intra-nasally (administration of oxygen in front of the nasal ostia vs cannula system inside the nasal vestibulum). The impact of cannula design on intra-nasal humidity, however, has not been investigated to date.
  
  
  OBJECTIVE
  First, to develop a system, that samples air from the nasal cavity and analyzes the humidity of these samples. Second, to investigate nasal humidity during pre-nasal and intra-nasal oxygen application, with and without humidification.
  
  
  METHODS
  We first developed and validated a sampling and analysis system to measure humidity from air samples. By means of this system we measured inspiratory air samples from 12 subjects who received nasal oxygen with an intra-nasal and pre-nasal cannula at different flows, with and without humidification.
  
  
  RESULTS
  The sampling and analysis system showed good correlation to a standard hygrometer within the tested humidity range (r = 0.99, P < .001). In our subjects intranasal humidity dropped significantly, from 40.3 ± 8.7% to 35.3 ± 5.8%, 32 ± 5.6%, and 29.0 ± 6.8% at flows of 1, 2, and 3 L, respectively, when oxygen was given intra-nasally without humidification (P = .001, P < .001, and P < .001, respectively). We observed no significant change in airway humidity when oxygen was given pre-nasally without humidification. With the addition of humidification we observed no significant change in humidity at any flow, and independent of pre- or intranasal oxygen administration.
  
  
  CONCLUSIONS
  Pre-nasal administration of dry oxygen achieves levels of intranasal humidity similar to those achieved by intranasal administration in combination with a bubble through humidifier. Pre-nasal oxygen simplifies application and may reduce therapy cost.
authors.affiliation: Department of Pulmonology, Intensive Care, and Sleep Medicine, Fachkrankenhaus Kloster Grafschaft, Schmallenberg, Germany. d.dellweg@fkkg.de
authors.forename: Dominic
authors.initials: D
authors.lastname: Dellweg
authors.forename: Markus
authors.initials: M
authors.lastname: Wenze
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Hoehn
authors.forename: Olaf
authors.initials: O
authors.lastname: Bourgund
authors.forename: Peter
authors.initials: P
authors.lastname: Haidl
mesh_terms: D057785:Catheters; D004867:Equipment Design; D006801:Humans; D006813:Humidity; D010102:Oxygen Inhalation Therapy / Q000295:instrumentation* / Q000379:methods
keywords: nasal humidity; nasal mucosa; nasal oxygen cannula; oxygen therapy