Pulmonary function testing
An average of 15 minutes was taken to perform reliable supine spirometry
after performing sitting spirometry. In the neuromuscular group, the
mean sitting FEV1% and sitting FVC% were 78% (SD
±21.9) and 75% (SD±20.5) respectively as shown in Table 3. The
percentage difference in ΔFVC between sitting and supine in these NMD
children was 9%.
Children breathing spontaneously had an FEV1% of 83%
(SD±21.9) and an FVC% of 78% (SD±20.5) and a mean drop in FVC% in the
supine position of 7% (SD±17.9). Children on nocturnal NIV had baseline
sitting FEV1% and FVC% values of 72%(SD±17.9) and
70%(SD±24.5), respectively, with a mean drop of 12% in the supine
position to an FVC% of 58(SD±18.8). Healthy controls had a baseline
sitting lung function of FEV1 % and FVC% of 95%
(SD±5.2) and 98% (SD±4.8), respectively, with a mean drop of 4% in
ΔFVC in the supine position, (p<0.001 compared to children
with NMD) (Table 3).
Amongst the 11 children who could not do spirometry, 3 children had
cognitive delay and were unable to perform acceptable and reproducible
spirometry in the sitting position. Another three children were excluded
because they did not have acceptable or repeatable spirometry. Five
children had severe restrictive lung disease (FVC<40%) and
were able to perform sitting spirometry but were excluded because of
poor spirometry technique in the supine position.