Histamine Applied Topically to the Nasal Mucosa Increases the Transmucosal Nitrous Oxide Exchange for the Middle Ear

Abstract

Objective Determine if the middle-ear trans-mucosal Nitrous oxide (N2O) exchange-rate is affected by nasal inflammation caused by topical application of histamine. Methods In a randomized, double-blind, crossover study, twenty adults were challenged intra-nasally with histamine (5 mg) and placebo on separate occasions. At each session, the 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 and blood O2-saturation were monitored and bilateral middle-ear pressure was recorded by tympanometry every minute. The primary outcome measure was the slope of the middle-ear pressure-time function for the 50% N2O:50% O2 breathing period which is a measure of the trans-mucosal N2O exchange-constant. The effects of Challenge Substance, Session and Period on the measured vital-signs and of Treatment, Session, Ear-Disease History and Test Ear on the pressure-time slopes were evaluated using repeated-measures ANOVAs. Results The post-challenge total-symptom-score and the slope of the middle-ear pressure-time function were greater after histamine when compared to placebo challenge. Of the signs, only heart-rate was affected, responding to Challenge Substance and Study Period. Conclusion The trans-mucosal N2O exchange-rate for the middle ear is increased during inflammation caused by nasal histamine exposure.

Allergy in pathogenesis of Eustachian Tube Dysfunction

“… 54 A recent randomized, double-blind study tested the effects of intranasal histamine and placebo stimulation on middle ear pressure balance and gas exchange performance, and found that histamine could cause inflammation of the local mucosa and the distal mucosa, including the ET mucosa, thereby affecting ET opening and causing ETD. 55 In addition, many studies have shown that the use of intra-aural antihistamines in sensitized rat models can reduce the accumulation of middle ear fluid, improve OME symptoms, and may be effective in treating ETD caused by allergies. 56 , 57 , 58 …”