Introduction:
The clinical review by members of the European Respiratory Society Oscillometry Taskforce1 identified that oscillometry may have a key role in the management of survivors of very preterm birth (delivered <32 weeks completed gestation).2Over the lifespan, survivors of very preterm birth report increased respiratory symptoms, including wheeze, inhaled asthma medication use and re-hospitalization during early childhood compared to their term-born counterparts.3 Lung function deficits, including reduced FEV1, and abnormal respiratory mechanics are reported throughout childhood and into adulthood.4-7 By school-age, ~50% of very preterm-born children are diagnosed with asthma5; up to five times increased odds than those born at term.8 Despite the high prevalence of asthma diagnoses in this patient group, preterm lung disease is typically non-atopic9 with low exhaled nitric oxide (FeNO)10, contrary to childhood asthma. Additionally, recent trials of inhaled corticosteroids (ICS) report only modest improvements in lung function.11
Even with ICS therapy a degree of airway reversibility exists for those born <32 weeks gestation.11 A significant bronchodilator response has been reported in about one third of those born preterm12, with the highest rates in those with a neonatal diagnosis of chronic lung disease of prematurity, bronchopulmonary dysplasia (BPD). Studies report 25-60% of school aged children with BPD respond to bronchodilators. 7,12-14Despite this, there are reports of preterm-born children being undertreated with bronchodilators, possibly due to the belief that respiratory symptoms in this group are an inevitable consequence of airway injury and remodelling.15 Further, recent findings from our group indicate that those most likely to respond to inhaled corticosteroids, display a degree of airway reversibility.16 A thorough assessment of the efficacy of short acting bronchodilators is likely to become key to optimal patient management in this group.
The response to inhaled bronchodilators is typically assessed using spirometry, however the assessment of the bronchodilator response by oscillometry may offer additional advantages in the evaluation of preterm lung disease. As highlighted by the recent ERS review5, there is evidence that oscillometry may be a useful tool in this patient group. At baseline, oscillometry outcomes are abnormal in those born very premature, with the worst abnormalities observed in those with bronchopulmonary dysplasia (BPD).6,17,18 Additionally, in those born <32 weeks gestation oscillometry outcomes correlate with respiratory symptoms5,18 and are sensitive to changes in lung function due to exposure to tobacco smoke.19High test feasibility may be of particular value in this population where patients are young and developmental delay is associated with severe respiratory disease.20 Despite these advantages, the utility of oscillometry for the assessment of bronchodilator responses in preterm lung disease has yet to be explored.
Whilst few studies currently exist examining the bronchodilator response by oscillometry in those born preterm,7,18 asthma studies have reported that an oscillometry assessment of the bronchodilator response may be better than spirometry at differentiating asthmatic from healthy children21,22 and identifying individuals with poor asthma control.23 Emerging evidence suggests that intra-breath oscillometry may identify a bronchodilator response in smokers and patients with COPD with greater sensitivity than spirometry.24 Due to its ability to detect changes in the small airways, it may be that oscillometry is a more sensitive test in assessment of the bronchodilator response in those born preterm, however this has yet to be determined.
This study aimed to assess the feasibility and sensitivity of detecting a bronchodilator response by spirometry and oscillometry using published cut-offs in a preterm population. To further our understanding of the interpretation of these tests, we aimed to investigate the correlations and agreement between reported outcomes, and their association with clinical symptoms. We hypothesised that a greater response to bronchodilators would be observed in those born preterm (by all methods). We further hypothesised that there would be a correlation between oscillometry and spirometry bronchodilator induced changes, but that oscillometry outcomes would correlate with symptoms and identify individuals with a bronchodilator response that would not have been identified by spirometry alone.