Oximetry and carbon dioxide screening for ventilatory requirements in children with spinal muscular atrophy type 1-3

Introduction

Despite disease modifying treatments (DMT), assisted ventilation is commonly required in children with Spinal Muscular Atrophy (SMA). Guidelines suggest screening with oximetry and transcutaneous carbon dioxide (TcCO₂) for sleep disordered breathing (SDB).

Aim

To determine the utility of pulse oximetry and TcCO₂ as a screen for SDB and the need for Non-Invasive Ventilation (NIV) in children with SMA type 1–3.

Methods

A prospective cohort study was conducted in Queensland, Australia. Full diagnostic PSG was completed in DMT naïve children with SMA. Pulse oximetry and TcCO₂ were extracted from PSG. Apnoea-hypopnoea indices (AHI) criteria were applied to PSG results to define the need for NIV. Abnormal was defined as: ≤3 months of age [mo] AHI≥10 events/hour; >3mo AHI ≥5 events/hour. Receiver operating characteristic curves were calculated for abnormal PSG and pulse oximetry/TcCO₂ variables, and diagnostic statistics were calculated.

Results

Forty-seven untreated children with SMA were recruited (type 1 n = 13; 2 n = 21; 3 n = 13) ranging from 0.2 to 18.8 years old (median 4.9 years). Oxygen desaturation index ≥4 % (ODI4) ≥20events/hour had sensitivity 82.6 % (95 % CI 61.2–95.0) and specificity of 58.3 % (95 % CI 36.6–77.9). TcCO₂ alone and combinations of oximetry/TcCO₂ had low diagnostic ability. The same methodology was applied to 36 children who were treated (type 1 n = 7; type 2 n = 17; type n = 12) and oximetry±TcCO2 had low diagnostic ability.

Conclusion

ODI4 ≥20events/hour can predict the need for NIV in untreated children with SMA. TcCO2 monitoring does not improve the PPV. If normal however, children may still require a diagnostic PSG. Neither oximetry nor TcCO₂ monitoring were useful screening tests in the children treated with DMT.