Monitoring nasal conductance by bilateral nasal cannula pressure transducers

Nasal obstruction is common and may disturb well-being during daytime and sleep. Its objective assessment by standard methods requires patient cooperation and inconvenient instrumentation. Therefore, the purpose of this study was to develop a novel, unobtrusive technique for continuous monitoring of changes in nasal conductance during natural breathing based on pressure recordings at the left and right nares. In ten volunteers, pressure swings derived independently from left and right nasal cannula were recorded at baseline, and after topical application of histamine and xylomethazoline. Nasal conductance was measured by means of epipharyngeal pressure recordings and face-mask pneumotachography as the reference standard. Decreases in nasal conductance were associated with changes in relative timing and shape of left and right nasal cannula derived pressure swings during breathing. This was reflected in decreases in the coefficient of cross-correlation between left and right nasal pressure signals. Diagnostic accuracy in detecting a fall in nasal conductance to <80% baseline by the maximal coefficient of determination from cross-correlation of left versus right nasal pressure was evaluated by receiver operator characteristics. The area under the curve was 0.88, 95% confidence interval 0.76 to 0.99, n = 40, P < 0.05 versus 0.5. We conclude that patterns of pressure swings derived from left and right nasal cannula may serve as a noninvasive means to detect changes in nasal conductance without requirement of patient cooperation.