Knowledge of short and longer-term repeatability of lung function in health and disease is essential to determine bronchodilator reversibility (BDR) thresholds and to recognise if changes in lung function represent disease progression, therapeutic intervention or normal variability.
Multiple-breath washout (MBW) indices (lung clearance index [LCI], conductive ventilation inhomogeneity [Scond]) and specific airways resistance (sRaw) were measured in healthy children and stable wheezers. Measurements were performed at baseline and after 20 minutes without intervention to assess repeatability and determine BDR thresholds. BDR was assessed by repeating baseline measurements 20 minutes after inhaled salbutamol.
Twenty-eight healthy controls, mean age 6.1 (SD 0.7)y and 62 wheezers 5.4 (0.6)y were tested. Baseline variability in MBW indices and sRaw was not significantly different between wheezers and healthy controls. Significant BDR was only observed in wheezers for Scond (16%); but in both wheezers (37%) and healthy controls (20%) for sRaw. Some wheezers and healthy controls demonstrated increases in MBW indices post-bronchodilator.
LCI and sRaw demonstrate low baseline variability in health and disease. Neither MBW indices nor sRaw are ideal for assessing BDR in young children with stable wheeze. These findings will help interpret effect of therapeutic interventions in children with respiratory diseases.
- Bronchodilator reversibility
- lung clearance index (LCI)
- multiple-breath washout (MBW)
- preschool children
- specific airways resistance (sRaw)