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.
|Original language||English (US)|
|Number of pages||8|
|Journal||American journal of respiratory and critical care medicine|
|State||Published - Jan 1 1996|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Critical Care and Intensive Care Medicine