Relationship between respiratory function and need for NIV in childhood SMA.
BACKGROUND
Spinal muscular atrophy (SMA) causes progressive respiratory muscle weakness but respiratory function (RF) in those using noninvasive ventilation (NIV) is not well described.


OBJECTIVE
To describe RF in childhood SMA and assess differences between those using and not using NIV.


METHODS
A cross-sectional study of childhood SMA assessed polysomnography (PSG), spirometry, forced oscillation technique (FOT), lung clearance index (LCI), sniff nasal inspiratory pressures, peak cough flow, maximal inspiratory and expiratory pressure, and NIV use and indication.


RESULTS
Twenty-five children (median age [interquartile range], 8.96 [5.63] years; 10 F) with SMA 1 (n = 3), 2 (n = 15), and 3 (n = 7) were recruited. Spirometry and FOT testing was feasible in children as young as 3 years. Ten (40%) required NIV, 5 for sleep-disordered breathing (SDB), and 5 initiated during lower respiratory tract infection (LRTI). Children requiring NIV were older (median, 10.52 vs 5.67 years; P < .02) with more abnormal forced vital capacity (FVC) z-score (-5.70 vs -1.39, P < .02), Rsr8 z-score (1.97 vs 0.50, P = .04), and LCI (8.84 vs 7.34, P = .01). Two had normal RF and SDB. For FVC z-score less than -2.5 and LCI greater than 7.5, the odds ratio for NIV was 10.70 (95% confidence interval [CI], 1.39-82.03) and 2 (95% CI, 0.40-10.31), respectively. All children with LCI greater than 8 used NIV. FVC z-score and LCI are associated with maximum transcutaneous carbon dioxide on PSG (r = 0.43, P < .001).


CONCLUSION
NIV is common in SMA. Normal RF does not exclude SDB. Children with more abnormal FVC and LCI should be considered at risk of starting NIV during/following an LRTI.
['Kapur|Nitin|N|', 'Deegan|Sean|S|', 'Parakh|Ankit|A|', 'Gauld|Leanne|L|0000-0003-0819-894X']
D000293:Adolescent D002648:Child D002675:Child, Preschool D003430:Cross-Sectional Studies D005260:Female D006801:Humans D007223:Infant D007231:Infant, Newborn D008297:Male D009134:Muscular Atrophy, Spinal D063087:Noninvasive Ventilation D017286:Polysomnography D012119:Respiration D012129:Respiratory Function Tests D012141:Respiratory Tract Infections D012891:Sleep Apnea Syndromes
respiratory function noninvasive ventilation sleep-disordered breathing neuromuscular disorders