Forced oscillation technique for monitoring of respiratory function in children with neuromuscular disease

Respiratory failure is the leading cause of death in patients with neuromuscular disease (NMD). Monitoring of lung function is central when assessing disease progression, but as disease advances, completing manoeuvres required for spirometry becomes more challenging. Forced oscillation technique (FOT), uses sound waveforms to measure lung function during tidal breathing. The aim of this pilot study was to examine how easily children with NMD performed FOT compared to spirometry and to examine the correlation between FOT and spirometry results. 36 children with NMD were recruited with parental consent to take part in this prospective study. Their median age was 13.5 (range 7.4-17.3) years and mean forced vital capacity (FVC) z-score was -2.9 (range -7.47 - -0.43). 34 of the children were male. Each performed spirometry and FOT on the same day. For each child, FVC, forced expiratory volume (FEV1), and FOT-derived airway resistance (R) were obtained from ≥3 attempts. The replicability of measurements was then analysed using Pearson's Χ² test. The FVC and R z-scores were analysed using the Pearson’s correlation coefficient and simple linear regression. 34/36 patients produced replicable R while only 22/36 patients produced replicable FEV1 (Χ² = 1.16, ns). The z-scores of FVC and R had a negative linear relationship with a correlation coefficient of -0.3 (p < 0.08). The proposed R equivalents to the FVC z-score cut off values of -2.5 and -4 were 0.11 and 0.17 respectively. This study suggests that children with NMD produce replicable results on FOT. There is a linear relationship between FVC and R which might make FOT a useful substitute for spirometry in the future.