Background: The subjective sensation of nasal obstruction is of great importance to the patient and surgeon because it is this symptom that causes the patient to present for investigation and treatment. Although there are several studies in the literature looking at the correlation (or lack of correlation) between objective and subjective measures of nasal obstruction, there is no information on the minimum objective change in obstruction measured as nasal airway resistance or flow, which can be detected by a patient. The aim of this study was to measure the minimum difference in unilateral airflow that can be reliably detected by a patient.
Methods: Sixty participants with a common cold were recruited. One hundred twenty unilateral measurements of objective and subjective nasal obstruction were obtained using the technique of posterior rhinomanometry and a 100-mm visual analog scale (VAS).
Results: Seventy-seven percent of the participants correctly discriminated between the high- and low-flow nasal passages using the VAS. Ninety-five percent of subjects correctly discriminated on the VAS between the high- and low-flow nasal passages when the difference inflow between the nasal passages was at least 100 cm3/s.
Conclusion: This study provides new knowledge about the limits of subjective sensation of nasal obstruction. At a level of 100 cm3/s difference in unilateral nasal flow, 95% of subjects with acute rhinitis can correctly identify the more obstructed nasal passage when using a VAS. With smaller differences in unilateral flow, the percentage of correct responses declines rapidly toward 50% as expected by chance alone.