Humidification of Inspired Oxygen Is Increased With Pre-nasal Cannula, Compared to Intranasal Cannula

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 inves-tigated 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. RE-SULTS: 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 admin-istration. 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. Key words: nasal humidity; oxygen therapy; nasal oxygen cannula; nasal mucosa. [Respir Care 2013;58(8): 1323–1328. © 2013 Daedalus Enterprises