Intra-breath respiratory mechanics of prematurity-associated lung disease phenotypes in school-aged children.

Abstract

Background: Intra-breath oscillometry potentially offers detailed information regarding airway function, with increasing magnitude of difference between resistance and reactance at end-expiration to end-inspiration potentially associated with obstructive airway disease, but less is known about specific respiratory mechanics in preterm-born children using this methodology. We investigated whether different spirometry phenotypes of prematurity-associated lung disease (PLD) have specific intra-breath oscillometry features.

Methods: 167 school-aged (7-12 years) children, 14 with prematurity-associated obstructive lung disease (POLD; forced expiratory volume in 1 s (FEV₁) 1/forced vital capacity (FVC) 1 1/FVC ≥LLN), 90 preterm controls (FEV₁ ≥LLN) and 52 term controls, performed intra-breath oscillometry at baseline, following maximal cardiopulmonary exercise testing and following post-exercise bronchodilation.

Results: Children with POLD showed greater resistance and more negative reactance throughout the respiratory cycle, including at zero-flow states of end-expiration and end-inspiration. The difference between end-expiration and end-inspiration did not show differences between groups until corrected for tidal volume, whereby children with POLD and pPRISm both demonstrated approximately two-fold greater difference compared to both preterm and term controls for resistance (2.24 and 2.22 versus 1.28 and 1.11 hPa·s·L^-1, respectively), and in particular a greater magnitude of difference for reactance for children with POLD versus preterm and term controls only (-1.58 versus -0.26 and 0.03 hPa·s·L^-1, respectively).

Conclusions: Intra-breath respiratory mechanics for preterm-born children with an obstructive lung phenotype have greater impedance throughout the respiratory cycle, features different to those observed in children with other wheeze phenotypes including preschool wheeze and asthma.