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Bronchial reactivity in infants in acute respiratory failure with viral bronchiolitis
G B Mallory1, E K Motoyama, A C Koumbourlis
1Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh, Pennsylvania.
Insights
Infants with severe respiratory syncytial virus (RSV)-associated bronchiolitis show significant airway reactivity. Bronchodilator treatment positively impacts this reactivity, improving outcomes in most affected infants.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Critical Care
Background:
- Airway reactivity and bronchodilator response in infants with respiratory failure remain debated.
- Respiratory syncytial virus (RSV)-associated bronchiolitis is a common cause of infant respiratory distress.
Purpose of the Study:
- To investigate airway reactivity and bronchodilator response in mechanically ventilated infants with severe RSV-associated bronchiolitis.
Main Methods:
- Mechanically ventilated infants with RSV bronchiolitis and healthy controls were studied.
- Deflation flow-volume (DFV) curves were measured before and after bronchodilator administration.
- Key parameters included forced vital capacity (FVC) and maximum expiratory flow rate at 25% of FVC (MEF25).
Main Results:
- Infants with bronchiolitis had lower baseline FVC and MEF25 compared to controls, indicating severe airway obstruction.
- Bronchodilator administration did not significantly alter FVC.
- MEF25 significantly increased by over 148% in most infants with bronchiolitis, suggesting positive bronchodilator response.
Conclusions:
- Most infants with severe RSV-positive bronchiolitis exhibit airway reactivity.
- Bronchodilator treatment can positively affect airway reactivity during the acute phase of severe RSV bronchiolitis.
Abstract:
Airway reactivity and the effects of bronchodilators in infants are controversial. We studied the response to bronchodilator treatment in 14 mechanically ventilated infants (mean age, 2.74 months; range, 0.6-5.9) in respiratory failure caused by respiratory syncytial virus (RSV)-associated bronchiolitis. Sixteen infants without lung disease, undergoing elective surgery, provided normal values. Maximum expiratory deflation flow-volume (DFV) curves were produced by manual inflation of the lungs with an anesthesia bag to a predetermined static airway pressure followed by rapid deflation with a negative airway pressure before and after administration of bronchodilator. At baseline, the bronchiolitis group had a forced vital capacity (FVC) of 34.5 +/- 3.6 ml/kg compared with 41.8 +/- 1.5 ml/kg in the normal group; maximum expiratory flow rate at 25% of FVC (MEF25) was 10.2 +/- 2.0 ml/kg/s compared with 27.3 +/- 2.0 ml/kg/s in the normal group. The clinical and radiologic impression was severe lower airway obstruction and air trapping. After administration of bronchodilator, FVC did not increase significantly, but MEF25isov increased by over 30% in 13 of 14 infants. Mean MEF25 increased by 148 +/- 43.2% to 21.7 +/- 3.9 ml/kg/s (P less than 0.02). These findings indicate that during the acute phase of severe RSV-positive bronchiolitis most infants have airway reactivity that responds positively to bronchodilator treatment.