Two-dimensional assessment of the nasal valve area cannot predict minimum cross-sectional area or airflow resistance

Background: Clinicians who manage nasal obstruction often comment on the shape and size of the nasal valve (NV) area. However, correlation of the symptoms of obstruction, nasal airflow dynamics, and the endoscopic appearance of the anatomic cross-sectional area of the NV is poorly understood. Endoscopic imaging and calculation of the NV area is investigated as a tool for either clinical or research use.

Objective: To describe and evaluate a two-dimensional measurement of the minimum cross-sectional area (MCA) of the NV by using endoscopic imaging.

Methods: A cross-sectional study of patients with symptoms of nasal obstruction who were undergoing nasal assessment was performed. The NV was measured with digital imaging taken from the endoscopy. Adobe Photoshop was used to calculate the digital MCA of the NV based on pixel count and a reference marker placed in the image field. Airway parameters were assessed by using a nasal obstruction visual analog scale, nasal airway resistance via rhinomanometry, and acoustic rhinometry derived MCA (acoustic MCA). Correlation of the digital MCA and airway parameters was made and interobserver correlation of the MCA measures was calculated.

Results: Thirty-three nasal airways were assessed: mean (standard deviation) digital MCA (0.28 +/- 0.13 cm(2)) and mean (standard deviation) acoustic MCA (0.51 +/- 0.15 cm(2)). Correlation of the digital MCA with visual analog scale was poor (Pearson r = 0.10, p = 0.56). Similar finding between digital and acoustic MCA was poor (Pearson r = 0.50, p = 0.56, respectively) despite a moderately strong interobserver correlation for the digital MCA (Pearson r = 0.79, p = 0.001).

Conclusion: Qualitative endoscopic assessment of the NV may help clinicians predict NV dysfunction but simple two-dimensional measures seemed to be of limited value in accurately assessing the three-dimensional NV quantitatively.