In moderate-to-severe asthma patients monitoring exhaled nitric oxide during exacerbation is not a good predictor of spirometric response to oral corticosteroid.

Background: The importance of monitoring exhaled nitric oxide (NO) in asthma remains controversial. Objective: To measure exhaled NO, postnebulized albuterol/ipratropium spirometry, and Asthma Control Test (ACT) during asthma exacerbation requiring 8- to 10-day tapering oral corticosteroid in nonsmoking patients with moderate-to-severe asthma on moderate-dose inhaled corticosteroid and long-acting β₂-agonist but not maintenance oral corticosteroid. Methods: After measuring the fraction of exhaled NO (Feno [ppb]) at 50, 100, 150, and 200 mL/s, the total Feno at 50 mL/s (ppb), large central airway NO flux (J′_awNO [nL/s]), and peripheral small airway/alveolar NO concentration (C_ANO [ppb]) were calculated and corrected for NO axial back-diffusion. Outpatient exacerbation required the patient with asthma to be afebrile with normal chest x-ray and white blood cell count. Results: Group 1 included 17 patients (6 men) with asthma, age 52 ± 12 years, studied at baseline, during 18 exacerbations with abnormal Feno at 50 mL/s, J′_awNO, and/or C_ANO, and post 8- to 10-day tapering 40 mg prednisone (recovery). Baseline: IgE, 332 ± 243 Kμ; total blood eosinophils, 304 ± 266 cells/μL; body mass index, 28 ± 6; ACT, 16 to 19; and FEV₁, 2.5 ± 0.7 L (86% ± 20% predicted); exacerbation: FEV₁, 1.7 ± 0.4 L (60% ± 17%) (P < .001); recovery: FEV₁, 2.5 ± 0.7 L (85% ± 13%) (P < .001). Group 2 included 11 (7 men) similarly treated patients with asthma, age 49 ± 14 years, studied at baseline, during 15 exacerbations with normal Feno at 50 mL/s, J′_awNO, and C_ANO. Baseline: IgE, 307 ± 133 Kμ; total blood eosinophils, 296 ± 149 cells/μL; body mass index, 28 ± 6; ACT, 16 to 19; and FEV₁, 2.7 ± 0.9 L (71% ± 12% predicted); exacerbation: FEV₁, 1.7 ± 0.6 L (54% ± 19%) (P < .006); recovery: FEV₁, 2.7 ± 0.9 L (70% ± 14%) (P = .002). On comparing group 1 versus group 2, there was no significant difference for baseline IgE, eosinophils, body mass index, and ACT and similar significant (≤.006) decrease from baseline in FEV₁ (L) during exacerbation and similar increase (≤.006) at recovery. Conclusions: Increased versus normal exhaled NO during outpatient exacerbation in patients with moderate-to-severe asthma on inhaled corticosteroid and long-acting β₂-agonist but not maintenance oral corticosteroid does not preclude a robust clinical and spirometric response to tapering oral prednisone. [Copyright &y& Elsevier]