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Pitfalls of open-access sleep medicine: a case of missed congenital central hypoventilation syndrome

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Clinical record

A 60-year-old woman was referred to the Princess Alexandra Hospital Sleep Disorders Centre in 2011 with a history of poor sleep despite continuous positive airway pressure (CPAP) for 4 years.

She had a general practitioner-referred home diagnostic sleep study performed in 2007 to investigate daytime somnolence. This showed severe obstructive sleep apnoea (OSA) with a saturation of oxygen nadir of 31%, and a CPAP device was recommended. In 2010, the patient had ongoing symptoms despite nightly CPAP, so her GP requested an in-laboratory CPAP study. This found ongoing severe hypoxia, similar to the previous study, so there was no change to treatment. It was not until symptoms of worsening sleepiness in 2011 that a sleep physician review was requested.

In early 2012, under sleep physician care, an in-laboratory study was performed with half the night in diagnostic mode to clarify the diagnosis of OSA and half the night with CPAP therapy over a range of pressures. The diagnostic phase showed OSA, which was controlled in the CPAP phase. However, there was ongoing hypercapnia, indicating that CPAP was not the appropriate ventilation modality and that complex bi-level ventilation was required. Bi-level ventilation is a form of non-invasive positive airway pressure that cycles between inspiratory and expiratory pressures to increase ventilation and thus control hypercapnia.…