Assessment of bronchodilator response by forced oscillation technique in a preterm infant with evolving bronchopulmonary dysplasia: A case report

Oscillatory mechanics in very preterm infants on continuous positive airway pressure support: Reference values

OBJECTIVE

To create reference values for respiratory system resistance (Rrs) and reactance (Xrs) measured by the forced oscillation technique (FOT) in nonintubated very preterm infants.

DESIGN

Retrospective analysis of data collected as part of prospective observational studies in two centers.

SETTING

Tertiary neonatal intensive care units.

PATIENTS

Non-intubated infants below 32 weeks' gestation age who did not develop bronchopulmonary dysplasia.

INTERVENTIONS

We applied FOT using a mechanical ventilator (Fabian HFOi; Vyaire) that superimposed small-amplitude oscillations (10 Hz) on a continuous positive airway pressure of 3 and 5 cmH₂ O. Measurements were performed during regular tidal breathing using a face mask.

MAIN OUTCOME MEASURES

We analyzed 198 measurements performed between 7 postnatal days and 40 weeks postmenstrual age (PMA) in 85 infants, with a median (Q1, Q3) gestational age of 30.43 (29.14, 31.18) weeks. Logarithmic transformations were applied to Rrs and Xrs, and the relationship between transformed impedance values and demographic factors was examined by backwards stepwise linear regression.

RESULTS

In univariable analysis, transformed Xrs was significantly associated with PMA, postnatal age, weight, and length, while Rrs was not. The best multivariable regression model estimating transformed Xrs (cmH₂ O*s/L) at continuous positive airway pressure (CPAP) = 5 cmH₂ O was: Ln(50 - Xrs) = 4.536 - 0.009 x PMA - 0.014 x weight z-score. SEE = 0.053, R²  = 0.36. The mean (SD) Rrs at CPAP = 5 cmH₂ O was 33.63 (5.28) cmH₂ O*s/L.

CONCLUSION

We have established reference values for Rrs and Xrs at 10 Hz in nonintubated preterm neonates on continuous positive airway pressure support.

Respiratory support strategies in the prevention and treatment of bronchopulmonary dysplasia

Neonates who are born preterm frequently have inadequate lung development to support independent breathing and will need respiratory support. The underdeveloped lung is also particularly susceptible to lung injury, especially during the first weeks of life. Consequently, respiratory support strategies in the early stages of premature lung disease focus on minimizing alveolar damage. As infants grow and lung disease progresses, it becomes necessary to shift respiratory support to a strategy targeting the often severe pulmonary heterogeneity and obstructive respiratory physiology. With appropriate management, time, and growth, even those children with the most extreme prematurity and severe lung disease can be expected to wean from respiratory support.

Oscillatory Mechanics Response to Inhaled Bronchodilators in Very Preterm Infants: A Retrospective Study

OBJECTIVES

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

STUDY DESIGN

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

RESULTS

The coefficient of repeatability was 7.5 cmH₂O∗s/L (21%) for respiratory system resistance and 6.3 cmH₂O∗s/L (21%) for respiratory system reactance. On average, respiratory system resistance did not change significantly following BD administration, though respiratory system reactance increased significantly (from -32.0 [-50.2, -24.4] to -27.9 [-38.1, -22.0] cmH₂O∗s/L, P < .001). Changes in respiratory system resistance or respiratory system reactance after BD were greater than the identified coefficient of repeatability 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.