Polysomnography (PSG) in children with NMD
PSG data were available within 6 months of spirometry for the 30 children with NMD. Mean (±SD) total sleep time was 351±8.8 min. The total AHI was 6.9 ±5.9/hour, obstructive AHI was 5.2±4.2 /hour and REM AHI 14.1±5.3 /hour. Only 2 children [7%] had a normal total AHI [<1/hr].(25) The average baseline SpO2 was 96 SD±5% and minimum saturation for the entire cohort was 88.4 SD±4.2%. The mean baseline transcutaneous [Tc] CO2 was 44mmHg (SD±5). The rise in TcCO2 from NREM to REM sleep in the entire cohort was 6 mmHg (SD±2.7) (Table 6).
Eight children with NMD were already established on non-invasive ventilation (NIV) when they were studied. Indications for NIV included recurrent chest infections requiring paediatric intensive care unit admissions (n=2) or evidence of sleep disordered breathing (n=6). The TcCO2 rise from NREM to REM sleep of 5 vs 9 mmHg, for children breathing spontaneously compared to those on nocturnal NIV.
There was no significant correlation between postural changes in spirometry and the rise in CO2 from NREM to REM sleep on PSG for the group as a whole (r-=0.04, p=0.8), the group spontaneously breathing (r=0.02, p=0.9), or for those established on NIV (r=0.13,p=0.74). The healthy controls did not have polysomnograms.