Impulse oscillometry in the diagnosis of subclinical obstructive airways disease in Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a rare genetic collagen disorder characterised by increased susceptibility to bone fractures. Several distinct subtypes differentiated by phenotype and mode of inheritance exist. Restrictive lung disease due to ribcage deformity may be seen in OI, and there is evolving interest regarding possible intrinsic pulmonary disease secondary to abnormal collagen function. Impulse oscillometry (IOS) measures airway resistance and reactance during tidal breathing, and can indicate the presence of airway disease. Adult patients with OI (N=22) were recruited to a single-centre observational cohort study to determine potential patterns of airway disease via IOS. Spirometry, gas exchange, and lung volume measurements were also attained in accordance with ERS technical standards. 54.5% (N=12) had evidence of airway obstruction on IOS across one or more indices. In those with increased total airways resistance (N=9), a mean R5Hz of 199.8% predicted was observed (range 155%-274%). Mean reactance (predicted X5Hz - X5Hz) was 0.21 kPa (range 0.15-0.29 kPa). Peripheral airway resistance (difference R5Hz – R20Hz) was abnormal in 50% (N=11) of all OI patients (mean 0.16 kPa, range 0.11-0.26 kPa). In comparison, spirometry detected obstruction in only 4.5% (N=1) by GOLD criteria (FEV1/FVC <0.7) and 9% (N=2) by FEV1/FVC < GLI LLN. MMEF25-75% was reduced in 33% (N=4) with IOS obstruction, corresponding with increased total and peripheral airway resistance in 75% (N=3). In summary, impulse oscillometry may reveal peripheral airway obstruction in a significant proportion of individuals living with OI, which may be undetected by traditional spirometry.