Assessment of the bronchodilator response
Oscillometry was more feasible than spirometry, with 95% of overall
participants obtaining acceptable measures pre- and post-bronchodilator
with oscillometry, compared to 85% for FEV1(p<0.001) and 69% for FVC (p<0.001). However, the
feasibility of achieving a successful bronchodilator assessment with
either test was similar in term and preterm groups (p>0.05,
Table 3).
A greater bronchodilator response was observed in the preterm group
compared to the term group via both spirometry and oscillometry (Table
3). A small but significant improvement in FEV1, but not
FVC, was observed, relative to term born controls with a mean difference
of 3.5% (95% CI 2.0 to 4.9; p<0.001). Similarly,
improvements were observed in the oscillometry measures
ΔRrs5 (MD= -4.9%, 95% CI -8.7 to -1.0, p=0.013),
ΔRrs5-20 (MD= -0.39, 95% CI -0.56 to -0.23,
p<0.001), ΔXrs5 (MD= 11.4%, 95% CI 5.8 to
17.0, p<0.001) and ΔAX (MD= -14.1%, 95% CI -22.6 to -5.7,
p=0.001).
Using published cut-offs, we
observed a bronchodilator response in 24.1% of those born ≤32 weeks
gestation by spirometry compared to 7.6% of term-born controls
(p=0.003). Oscillometry detected a bronchodilator response in 16.4% of
those born preterm, compared to 4.3% of term-born controls (p=0.009).
Intrabreath oscillometry revealed that the magnitude of the change in
inspiratory reactance (X10insp) and expiratory reactance
(X10exp) following bronchodilator was greater in those
born preterm (Table 3). The magnitude of this change was however
proportional across the breath cycle, with negligible within breath
differences in reactance (X10insp-exp) (MD= -0.01, 95%
CI -0.1208 to 0.101, p=0.861) (Table 3). No significant bronchodilator
induced decrease in inspiratory or expiratory resistance were observed
in the preterm group, relative to the term-control group (Table 3).