Paediatric sleep investigations: polysomnography, sleep-study interpretation and MSLT — structured case

Station 1 — choosing the investigation

Asked how I would investigate this snoring, inattentive, poorly growing preschooler, I explain that her story is a breathing problem, so I want an overnight study rather than a daytime test. I would arrange attended in-laboratory polysomnography as the reference standard because it records brain and breathing together and can classify and grade the events; where laboratory access is limited, oximetry or a limited study can confirm clearly positive disease but a negative result would not exclude apnoea in so symptomatic a child. [1] [3]

Station 2 — interpreting the report

The report shows an obstructive apnoea-hypopnoea index of 9 events per hour, a central index of 0.3, an oxygen saturation nadir of 84 per cent and a peak carbon dioxide of 45 mmHg, with adequate total and rapid-eye-movement sleep. I interpret this as moderate-to-severe obstructive sleep apnoea, because in a child an obstructive apnoea-hypopnoea index above one event per hour is abnormal and paediatric rather than adult thresholds apply, and the low central index confirms the events are obstructive. [6] [2]

Station 3 — obstructive versus central and carbon dioxide

Asked how I know the events are obstructive and whether she is hypoventilating, I explain that the effort belts make the call: airflow falls while chest and abdominal effort continue in an obstructive event, whereas both stop together in a central event. Her carbon dioxide is not sustainedly high, so there is no sleep hypoventilation; I stress that I would never read a normal saturation as proof of normal ventilation, because hypoventilation can hide behind an acceptable oximetry when carbon dioxide is not recorded. [7] [10]

Station 4 — treatment and follow-up

For this moderate-to-severe obstructive disease with adenotonsillar hypertrophy, I would recommend adenotonsillectomy as first-line treatment, with the severity guiding inpatient post-operative monitoring given her age and the degree of desaturation. I would arrange a post-operative sleep study to confirm resolution because her disease is significant, and I would treat any residual obstruction with continuous positive airway pressure and address contributory factors. [1] [2]

Station 5 — the sleepy adolescent pivot

The examiner pivots to a fifteen-year-old with severe daytime sleepiness and knee-buckling on laughing whose overnight breathing study is normal. I explain that this raises narcolepsy and warrants a multiple sleep latency test, but only after two weeks of documented adequate sleep, withdrawal of rapid-eye-movement-suppressing drugs where safe, and an adequate overnight study to exclude apnoea and confirm sleep; a short mean sleep latency with two or more sleep-onset rapid-eye-movement periods would support the diagnosis once insufficient sleep and a delayed sleep phase are excluded. [5] [9]