Forced Oscillation Technique: a surrogate measure of lung function in
neuromuscular disease patients?
Abstract
Introduction Spirometry plays an important role in the assessment of
possible respiratory failure in children with neuromuscular disorders
(NMDs). However, obtaining reliable spirometry results is a major
challenge. We studied the relation between Forced Oscillation Technique
(FOT) and spirometry results. FOT is an easy, non-invasive method to
measure respiratory mechanics, i.e. respiratory resistance R and
respiratory reactance X. We hypothesized an increased resistance R and
reduced reactance X in patients with more reduced lung function. Methods
In this prospective single center study we included all children with
NMDs able to perform spirometry. We consecutively measured respiratory
resistance R and reactance X at 5, 11 and 19 Hz and (Forced) Vital
Capacity, Peak Expiratory Flow. Spearman correlation coefficients were
calculated and regression curves were estimated. Results We included 148
patients, with a median age of 13 years (IQR 8-16). All correlation
coefficients were statistically significant with p = 0.000. A negative
correlation was found between resistance R and spirometry outcomes
(spearman correlation coefficient (ρ) between -0.5 and -0.6). A positive
correlation was found between reactance X (i.e. less negative outcomes)
and spirometry outcomes (ρ between 0.4 and 0.6). Highest correlation was
found at lower frequencies. Regression analysis showed a non-linear
relation between FOT and spirometry results. Conclusion We found a
non-linear relation between FOT and spirometry results with increased
resistance R and reduced reactance X in patients with more restrictive
lung function decline. Given the difficulties with performing
spirometry, FOT may be a promising surrogate measure of lung function.