PROBLEM: There is no consensus regarding the best approach to select patients for septoplasty. Patient dissatisfaction after septoplasty implies that clinical examination alone is inadequate to detect a clinically relevant nasal septal deviation (NSD). Objective testing provides an in-depth analysis of nasal obstruction and its underlying anatomic causes but it is effort consuming, requires training and it is not widely available.AIM: We studied the role of bilateral simultaneous nasal spirometry (BSNS) in the preoperative selection of patients for septoplasty.PATIENTS, SUBJECTS AND METHODS: Thirty patients with nasal obstruction and NSD were assessed by subjective measures and BSNS before and after septoplasty. The decongested nasal partitioning ratio (NPR) was used as a measure of the degree of NSD. Thirty healthy controls were recruited for providing a normal range of NPR values.RESULTS: All patients were subjectively improved after septoplasty but only those with NPR out of the normal limits had a significant reduction of NPR. Patients with unilateral symptoms and NPR beyond normal limits were also able to identify the more obstructed side preoperatively. For this group of patients, physicians were able to identify the convex side of NSD preoperatively. No correlation between subjective measures of nasal obstruction or airflow asymmetry and NPR was observed.CONCLUSION: BSNS is a rapid, easily interpretable, noninvasive technique, which identifies patients with large NSDs who, irrespective of concomitant mucosal factors of nasal obstruction, warrant septoplasty. BSNS is not applicable in cases with a septal perforation or an S type septal deviation, it cannot detect an insufficient nasal valve and it does not substitute rhinomanometry or acoustic rhinometry.