Limitations
Limitations to our study included involvement of only a single site
where children were recruited from one neuromuscular clinic resulting in
a small sample size even though all children with NMD who fulfilled
inclusion criteria were approached to participate in the study. In
addition, ccorrelations between spirometry and PSG parameters may have
been apparent if PSG data had been obtained in the control group. Whilst
historical cohorts looking at supine spirometry have included similar
numbers of patients, we recognize that larger numbers of patients are
needed. Children with severe restrictive lung disease
(FVC<40%) who were already established on NIV were unable to
perform reliable spirometry in both sitting and supine positions. Supine
spirometry is therefore not useful in these children on the more severe
end of the spectrum where it may be uncomfortable, impractical und
unhelpful in predicting SDB. Lastly, the cross-sectional nature of the
study did not allow examination of the relationship between supine
spirometry and evolution of
respiratory
weakness over time.