Objective: To evaluate long-term pulmonary function and airway hyperresponsiveness (AHR) in children following acute influenza lower respiratory tract infection (LRI).

Material and Method: Children aged 8 to 18 years who had no underlying disease and were discharged from the hospital for acute influenza LRI at least one year ago were studied. Pulmonary function tests (PFT) (spirometry, body plethysmography) and exercise stress tests were undertaken. Exercise-induced AHR was evaluated by serial spirometries after the maximal exercise.

Results: Eighteen children (mean age 12.2±2.6 years, 67% male) were studied. The meantime interval after recovery from acute influenza LRI was 2.5±1.0 years. Fifty-six percent had acute influenza LRI at least two years ago. Abnormal PFT compatible with mild restrictive defect was found in one child who had H1N1-2009 influenza pneumonia 3.2 years ago. Maximal exercise was achieved in 15 children. Exercise-induced AHR was demonstrated in three (20%). All of them had acute influenza LRI more than two years ago.

Conclusion: Residual lung function defect and AHR could be found in normal children who had acute influenza LRI more than one year ago. Monitoring of pulmonary function and AHR would be helpful for appropriate respiratory care in otherwise asymptomatic children previously hospitalized with acute influenza LRI.

Keywords: Children, Airway hyperresponsiveness, Influenza, Lung function, Exercise stress test, Pneumonia