Fig 1. The differences of preoperative nasal nitric oxide (nNO) levels between study groups.

Comparison of preoperative nNO on the (A) lesion side and (B) non-lesion side among the groups was analyzed. Data were expressed as the mean ± standard error of mean (SEM). CRSsNP = chronic rhinosinusitis without nasal polyps; CRSwNP = chronic rhinosinusitis with nasal polyps. ^*P < 0.05, ^**P < 0.01, Mann–Whitney U test.