P89 Impulse oscillometry in children with bronchiectasis-correlation of R5(reversibility) and R5-R20(reversibility) with AX

Abstract

<h3>Introduction</h3> Impulse oscillometry is an effort independent test done during tidal breathing. It requires minimal cooperation and is suitable for children five years and less. IOS is a validated test for assessment of distal airway obstruction. Low frequency(5Hz) impulse travels through proximal airway all the way to the distal or small airway; whereas a high frequency(20Hz) impulse reaches the proximal airways only. Difference of resistance at lower and higher frequency (R5-R20) and area under reactance (AX) are markers of small airway disease; and are superior to conventional spirometry. In adults, AX has been reported as a more sensitive marker compared to R5 and R5-R20. <h3>Methods</h3> This is a retrospective analysis of children who underwent impulse oscillometry at our tertiary care centre. We performed IOS manoeuvres in accordance with the American Thoracic Society standards. Jaeger MS-IOS Digital Viasys was used for IOS. It was calibrated using a 3L syringe before measurements. All study subjects were asked to breathe tidally for 30 seconds for IOS manoeuvre. Recommended coherence values (r2 &gt; 0.6 at 5 Hz and r2 &gt; 0.9 at 20 Hz) were used as markers of good technique. A variability of 10% for two out of three attempts was deemed acceptable. Bronchodilator reversibility was assessed by giving 400 mcg of salbutamol by a metered dosed inhaler through a spacer device and then measuring lung function fifteen minutes later. <h3>Results</h3> Our study sample size was 44(M=18, F=26). Children with a confirmed diagnosis of CF(n=32) or PCD(n=12) were included in this study. There were 14 children with bronchiectasis. Mean age and median height for the whole population was 8.1 years and 124 cm respectively. In children with bronchiectasis, both R5 reversibility (r=0.46, p=0.028) and R5-R20 reversibility (r=0.50, p=0.012) strongly correlated with AX. In children without bronchiectasis, R5 reversibility(r=0.12) and R5-R20 reversibility(r=0.28) had a weak positive correlation with AX. <h3>Conclusion</h3> This is the first study reporting IOS parameters in children with bronchiectasis. Both R5 and R5-R20 reversibility can be interchangeably used to diagnose reversible distal small airway obstruction in children with CF or non-CF bronchiectasis. <h3>Reference</h3> Galant, Stanley P, <i>et al</i>. ‘The case for impulse oscillometry in the management of asthma in children and adults.’ Asthma, &amp; Immunology vol. <b>118</b>,6 (2017): 664–671.