CLINICAL UPDATE
Tests to assess sleep apnoea
By Dr Sina Keihani, Respiratory and Sleep Disorders Physician, Leeming.
O
bstructive Sleep Apnoea (OSA) is undiagnosed in up to 75% of sufferers. There has recently been a huge growth of groups beyond the relatively small specialised services and traditional sleep labs. To assist health professionals, the Australian Sleep Association (ASA) has now published excellent guidelines for Sleep Studies and CPAP delivery. Accurate assessment of OSA severity is critical because severity correlates closely with risk of future sequelae, including coronary artery disease, stroke and mortality, as well as predicting success with therapies.
Working out pre-test probability of significant OSA is important. Validated tools simplify this process when there is clinical doubt (e.g. OSA-50 or Belin Qn). Assessment also seeks to identify modifiable risk factors, co-existing sleep problems, patient preference for testing and prospective therapies.
Sleep testing Level 1 (attended lab) studies are the reference standard. Advantages include video recording, verification of patient and head posture, real time signal integrity check, and CO2 monitoring. Testing can be used to monitor therapy. Level 2 (portable polysomnographs) are reimbursed once a year by Medicare provided: 7 or more channel recording; prior need established by a qualified Sleep Physician; in someone deemed high risk of significant OSA; and as a part of a comprehensive pathway (usually infers Sleep Physician review). Set-up by a qualified technician assists success; reported failure rate is 7-10% and the Apnoea Hypopnoea Index (AHI) may be underestimated by about 10%. Unsuitable patients are those with neuropsychological impairments, inappropriate home environment, suspected hypoventilation or other co-existing sleep disorders, and other discretionary situations e.g. suspected central sleep apnoea or pure ‘mouth breathers’. Limited channel recording (portable, 2-3 signals) lack critical information such as time asleep and often use the manufacturer’s automated processing to derive the AHI rather than manual assessment. Accuracy is uncertain, hence these tests are not useful at ruling out OSA (false negative) but an obviously positive test is not usually false.
Using expertise Basic studies can be offered through community groups with variable training and expertise, often with direct links to CPAP sales. If the program is not patient-focused there is a danger here of poor adherence and a lost opportunity. The ASA recommends against clinicians being engaged in the diagnosis of OSA while deriving income from the business of CPAP provision, and vice versa. It is important to differentiate OSA from the syndrome. An estimated 25% of patients with OSA on test actually require specific therapy. Furthermore, there are no uniform accepted criteria for severity scoring of sleep studies hence being familiar with the particular lab’s index is an important consideration (e.g. AHI or Respiratory Distress Index). Primary care involvement and direct testing accessibility brings key challenges. Assessment ultimately aims to identify those with treatmentrequiring OSA syndrome. Because clinical interpretation and context is vital, knowledge, expertise and adequate specialist support is the key to a successful model of care. Author competing interests: No relevant disclosures. For any clarification, contact author on Tel 6161 7647
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PIVET MEDICAL CENTRE Specialists in Reproductive Medicine & Gynaecological Services
FERTILITY NEWS
by Medical Director Prof John Yovich
&KDQFH RI SUHJQDQF\ UHà HFWHG E\ HPEU\R TXDOLW\ ‌ up to a point? The past decade has seen vastly improved results in IVF, mainly as a consequence of improved laboratory conditions including better culture media systems enabling development through to the day-5 blastocyst stage. Rising implantation rates have now enabled a focus on SET – single embryo transfers; Australia being the world leaders in this endeavour reducing multiple pregnancy rates to under 10% (compared to 30% in the USA and 20% in the UK and Europe). At PIVET current rates are under 5% whilst maintaining pregnancy rates in the top quartile. Applying the Gardner scoring system for blastocysts shows that the highest grades i.e. 4AA and 5AA, implant at 50-70% rates, the higher levels dependent upon optimal luteal support schedules. At the recent ESHRE meeting in Munich, it appears even higher implantation rates can be achieved by genetic screening of embryos to exclude A Day-5 Blastocyst with Gardner score 4AA aneuploidies which, indicating high quality rating of trophectoderm inner cell mass with full blastocoele cavity like Trisomies 21, 18 & and but not yet hatching 13 and Monosomy X, can be present even in top-scoring embryos. Whilst PGS on Day-3 embryos using FISH technology for 6-8 FKURPRVRPHV SURYHG QRQ EHQHÀFLDO WKH FXUUHQW GHEDWH FHQWUHV on Day-5 embryo biopsy with full chromosomal screening using array platforms such as CGH or the more sophisticated SNP array. The technology is moving forward rapidly with next generation massively parallel DNA sequencing. This can now be undertaken with relatively inexpensive desktop instruments such as VeriSeq which can detect even small chromosomal deletions. None-the-less, it appears that embryo quality assessment covers at best 80% of the implantation story and there remains a need for further research concerning the important issue of endometrial receptivity – both subtle uterine anomalies as well as endometrial synchrony factors may require correction.
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