title: Nasal contribution to exhaled nitric oxide at rest and during breathholding in humans.
abstract: We characterized the nasal contribution to exhaled nitric oxide (NO) at rest and during breathholding in humans. Exhaled NO was greater during nose breathing (141 +/- 17 nl/min/M2, mean +/- SEM) compared with mouth breathing (68 +/- 6 nl/min/M2, n = 8, p < 0.001). After voluntary closure of the soft palate (VCSP) to eliminate nasal NO, exhaled NO from the mouth decreased further (30 +/- 4 nl/min/M2, p < 0.001). Release of NO into nasal passages during VCSP (217 +/- 19 nl/min/M2) was greater than exhaled NO during nasal breathing (141 +/- 17 nl/min/m2, p < 0.001), suggesting that nasal NO is taken up by the respiratory tract. During mouth breathing or nose breathing, NO concentrations sampled with a bronchoscope were higher in the nasopharynx than at the epiglottis or in the trachea in five subjects. Increased peak exhaled NO after a breathhold (33 +/- 7 ppb) was reduced (10 +/- 4 ppb, p < 0.001) after balloon occlusion of the nasopharynx. NO concentration during breathholding increased to a greater extent in the nasopharynx than in the pharynx or trachea. We conclude that the majority of exhaled NO at rest and during a breathhold originates in the nasopharynx.
authors.affiliation: Medical Service, Portland Veterans Administration Medical Center, Oregon 97201, USA.
authors.forename: B
authors.initials: B
authors.lastname: Kimberly
authors.forename: B
authors.initials: B
authors.lastname: Nejadnik
authors.forename: G D
authors.initials: GD
authors.lastname: Giraud
authors.forename: W E
authors.initials: WE
authors.lastname: Holden
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009058:Mouth Breathing; D009297:Nasal Mucosa / Q000378:metabolism*; D009305:Nasopharynx; D009569:Nitric Oxide / Q000032:analysis / Q000378:metabolism*; D010614:Pharynx; D012119:Respiration; D014132:Trachea
chemical_list: D002245:Carbon Dioxide; D009569:Nitric Oxide