Use of a limited-channel device for obstructive sleep apnoea diagnosis in a tertiary sleep disorders centre.

BACKGROUND: A major impediment to the provision of obstructive sleep apnoea (OSA) treatment is reliance on labour-intensive and costly laboratory-based polysomnography (PSG). AIMS: To investigate if measurement of oximetry and nasal flow through the ApneaLink device (AL) could identify patients with moderate-severe OSA among those referred for PSG to a tertiary sleep service. METHODS: New referrals to The Prince Charles Hospital Sleep Disorders Centre were assessed for suitability. Demographics, anthropometrics, Epworth Sleepiness and OSA50 scores were collected. Exclusion criteria included age <18 years, pregnancy, significant cognitive impairment, poorly controlled psychiatric disorder, domiciliary oxygen and prior OSA treatment. Participants underwent concurrent type 1 PSG and AL assessments. RESULTS: One hundred participants had a mean age of 55 years (standard deviation 17) and were 49% male. Forty-eight (48%) had moderate-severe OSA on PSG. Composite variable AL 3% oxygen desaturation index ≥16 and AL apnoea-hypopnoea index (AHI) ≥15 had receiver operator characteristic area under the curve of 0.87, sensitivity of 80% and specificity of 94% for PSG AHI ≥15. The three false-positives seen with this composite variable had PSG AHI 11-14 and Epworth Sleepiness Score 6-17. The various composites of AL, anthropometric and questionnaire variables did not improve the AUC or specificity but did improve sensitivity. CONCLUSIONS: AL is useful in the diagnosis of moderate-severe OSA in patients referred to a tertiary sleep disorders centre. This could lessen reliance on PSG, expedite OSA care, lead to significant cost savings and make diagnosis of OSA more available in non-urban areas.

Measuring leg movements during sleep using accelerometry: comparison with EMG and piezo-electric scored events.

Periodic Limb Movements during Sleep (PLMS) can cause significant disturbance to sleep, resulting in daytime sleepiness and reduced quality of life. In conventional clinical practice, PLMS are measured using overnight electromyogram (EMG) of the tibialis anterior muscle, although historically they have also been measured using piezo-electric gauges placed over the muscle. However, PLMS counts (PLM index) do not correlate well with clinical symptomology. In this study, we propose that because EMG and piezo derived signals measure muscle activation rather than actual movement, they may count events with no appreciable movement of the limb and therefore no contribution to sleep disturbance. The aim of this study is thus to determine the percentage of clinically scored limb movements which are not associated with movement of the great toe measured using accelerometry. 9 participants were studied simultaneously with an overnight diagnostic polysomnogram (including EMG and piezo instrumentation of the right leg) and high temporal resolution accelerometry of the right great toe. Limb movements were scored, and peak acceleration during each scored movement was quantified. Across the participant population, 54.9% (range: 26.7-76.3) and 39.0% (range: 4.8-69.6) of limb movements scored using piezo and EMG instrumentation respectively, were not associated with toe movement measured with accelerometry. If sleep disturbance is the consequence of the limb movements, these results may explain why conventional piezo or EMG derived PLMI is poorly correlated with clinical symptomology.