Oscillatory mechanics response to inhaled bronchodilators in very preterm infants: a retrospective study.

OBJECTIVE: To identify short-term repeatability of forced oscillation technique (FOT) measurement of lung function, assess the lung function response to bronchodilators (BD) by FOT, prove the concept that only some very preterm infants manifest a change in lung mechanics in response to BD.

STUDY DESIGN: We retrospectively analysed respiratory system resistance (Rrs) and reactance (Xrs) measured by FOT (Fabian HFOi, Vyaire). The measurement short-term repeatability was assessed in 43 patients on 60 occasions; BD responsiveness was assessed using a different dataset, including 38 measurements in 18 infants. The coefficient of repeatability (CR) was calculated as twice the SD of differences between measurements performed 15 minutes apart. We assessed BD responsiveness by measuring Rrs and Xrs before and 15 minutes after administering 200 mcg/kg of nebulised salbutamol. A positive response was defined as an improvement in Rrs or Xrs greater than the identified CR.

RESULTS: The coefficient of repeatability was 7.5 cmH2 O*s/L (21 %) for Rrs and 6.3 cmH2 O*s/L (21 %) for Xrs. On average, Rrs did not change significantly following BD administration, though Xrs increased significantly (from -32.0 (-50.2, -24.4) to -27.9 (-38.1, -22.0) cmH2 O*s/L, p < 0.001). Changes in Rrs or Xrs after BD were greater than the identified CR in 8 infants (44 %) on 13 (34%) occasions.

CONCLUSIONS: We identified a threshold to assess BD responsiveness by FOT in preterm infants. We speculate that FOT could be used to assess and personalize treatment with BD.