NASAL-MUCOSA INFLAMMATION-INDUCED BY OXYGEN ADMINISTRATION IN HUMANS

Background: The effect of oxygen toxicity in human airways is still po orly documented. We prospectively evaluated the inflammatory reaction induced by nasal oxygen exposure in an experimental setting. Methods: Healthy subjects without nasal symptoms were exposed to high FIO2 duri ng 5 h. Oxygen was delivered from a tank at a flow of 4 l/min to one n ostril of each subject and both nostrils were studied. Mucociliary cle arance was measured as saccharine nasal transit time (SNTT). Nasal lav age was performed with 5 mi normal saline and the fluid recovered was processed for cytology and measurements of cytokines concentrations: T NF alpha, IL-6, IL-8 and soluble ICAM-1. Under local anaesthesia, biop sies were performed for immunochemistry and electron microscopy. Resul ts: After oxygen exposure mucociliary clearance decreased and SNTT inc reased from 16 [9-21] to 20.5 [14-32] min (median and extremes; P<0.1) . In the lavage fluid, concentration of IL-6 was higher in the oxygen- exposed nostril (40.5 [11-128] pg/ml) than in the non-exposed one (7 [ 0-34] pg/ml; P<0.05). There was also a trend for a higher IL-8 in the exposed than in the non-exposed nostril, (respectively 501 [214-587] p g/ml and 214 [122-616] pg/ml, P<0.08), and for a higher number of poly morphonuclear cells in exposed nostril. In the mucosal biopsies substa nce P was not found, but ICAM-1 expression was higher in the mucosa an d submucosa of the exposed nostrils where mast cells were also more ab undant and showed piecemeal degranulation. Conclusion: In summary, we found clinical, functional and biological evidence of ongoing nasal in flammation following high FIO2 inhalation for 5 h. Since the histology and behaviour of nasal and bronchi mucosa are very similar, the same inflammatory events are likely to be occurring in the bronchi upon hig h concentrations of inhaled oxygen.