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.