Bronchodilator responsiveness testing using raised volume forced expiration in recurrently wheezing infants

Area of Science:

• Pediatric Pulmonology
• Respiratory Physiology

Background:

• Infant lung function testing is challenging due to volume shifts.
• The raised volume forced expiration technique (RVFET) was developed to minimize lung volume variability.
• Detecting bronchodilator responsiveness in infants with recurrent wheeze is clinically important.

Purpose of the Study:

• To evaluate the efficacy of the RVFET in detecting bronchodilator effects in infants.
• To assess changes in lung function parameters (FEV0.75, FVC, FEF75%) following bronchodilator administration in infants with and without recurrent wheeze.

Main Methods:

• 22 infants with recurrent wheeze and 5 healthy infants underwent RVFET.
• Lung function was measured at baseline and after inhaling 500 microg salbutamol via MDI and spacer.
• Measurements included forced expiratory volume in 0.75 s (FEV0.75), forced expiratory vital capacity (FVC), and forced expiratory flow at 75% of FVC (FEF75%).
• A placebo group received aerosol without medication.

Main Results:

• No significant changes in FEV0.75, FVC, or FEF75% were observed after salbutamol administration compared to baseline or placebo.
• A significant increase in heart rate was noted post-salbutamol, indicating drug absorption.
• The RVFET did not reveal bronchodilator-induced changes in infant lung function.

Conclusions:

• The RVFET, despite its design to reduce lung volume shifts, did not demonstrate bronchodilator responsiveness in this cohort of infants.
• Infant lung function may not change significantly with bronchodilators, or the RVFET is not sensitive enough to detect these changes.
• Lung volume shifts are unlikely to be the sole reason for the lack of observed bronchodilator response in infants.