Abstract
Determine if the middle ear (ME) trans-mucosal nitrous oxide (N2O) gas exchange rate can be pharmacologically modulated by the nasal application of a vasoconstrictor.
In a randomized, double-blind, crossover study, 20 adults received a nasal spray challenge containing either oxymetazoline or saline (placebo). At each session, subjects were fitted with a non-rebreathing mask and breathed room air for 20 minutes, 50% N2O:50% O2 for 20 minutes, and 100% O2 for 10 minutes. Throughout, heart rate, blood pressure (BP), and blood O2 saturation were monitored, and bilateral ME pressure was recorded by tympanometry every minute. The primary outcome measure was the slope of the ME pressure-time function for the experimental period, a direct measure of the transMEM N2O exchange constant. The effects of treatment, session, and period on the measured vital signs and of treatment, session, disease history, and ear on the ME pressure-time slopes were evaluated for statistical significance using repeated measures ANOVAs.
The analysis documented a significant effect of period on O2 saturation (N2O > room air, P = .03) and of treatment on blood pressure (oxymetazoline > placebo, P < .02) and the ME pressure-time slope (placebo > oxymetazoline, P = .05).
The exchange rate across the ME mucosa of inert gases can be decreased by topical treatment of the nasal mucosa with oxymetazoline.