Obstructive Sleep Apnoea — Written Clinical Reasoning

SAQ 1 — Severe OSA in a Commercial Driver: Diagnosis, Management, and the Driving Duty (25 marks, 30 minutes)

Prompt: Outline your approach to this patient. Include how you would confirm the diagnosis and grade severity, your immediate and long-term management plan, how you would address CPAP adherence, the evidence regarding cardiovascular outcomes with CPAP, and your medico-legal obligations regarding his commercial driving licence. Include the evidence base for each major decision. [1]

Model Answer

Confirming the diagnosis and grading severity (4 marks): [1]

The clinical picture — loud snoring, witnessed apnoeas, excessive daytime sleepiness (Epworth 17, well above the abnormal threshold of 10), and a high pre-test probability on STOP-BANG criteria (obesity, male gender, observed apnoeas, hypertension, age over 50, neck circumference likely over 40 cm) — is classic for severe obstructive sleep apnoea [5]. The home sleep apnoea test shows an apnoea-hypopnoea index of 42 events per hour, which is over 30 and therefore severe, with significant desaturation to 78 percent.

A home sleep apnoea test is acceptable in a patient with a high pre-test probability of moderate-to-severe OSA and no complex comorbidity. However, given his atrial fibrillation and resistant hypertension, some units would obtain a full in-laboratory polysomnography to characterise the burden precisely and exclude central apnoeas, and to stage sleep architecture. I would discuss this with the sleep laboratory. The Epworth Sleepiness Scale quantifies the consequence — sleepiness — and a score of 17 out of 24 confirms severe excessive daytime sleepiness [1].

Immediate and long-term management plan (6 marks): [1]

1. CPAP is first-line for severe symptomatic OSA. I would arrange CPAP titration (in-laboratory or auto-titrating), with attention to mask fit, heated humidification, and structured early follow-up. CPAP acts as a pneumatic splint, holding the upper airway open throughout the respiratory cycle, and reduces daytime sleepiness, blood pressure, snoring, and improves quality of life. [1]

2. Lifestyle measures for all patients — weight loss is the single most effective lifestyle intervention, and a 10 percent reduction in body weight can reduce the AHI by approximately 50 percent. Avoid alcohol and sedatives before sleep, encourage lateral sleep positioning, and advise smoking cessation. [1]

3. Manage the cardiometabolic comorbidities. His resistant hypertension should be optimised in conjunction with general medicine or nephrology, acknowledging that CPAP may lower blood pressure modestly over months. His atrial fibrillation should be managed on its merits (rate or rhythm control, anticoagulation by CHA2DS2-VASc), with the expectation that treating the OSA may reduce recurrence after a rhythm-control strategy. Screen for diabetes and dyslipidaemia. [1]

4. Weight management. Given his body mass index of 36 and severe disease, I would refer to a multidisciplinary weight-management service and discuss bariatric surgery, which produces substantial weight loss and can significantly reduce or resolve OSA in selected morbidly obese patients. [1]

5. Alternatives if CPAP is not tolerated. A mandibular advancement splint is the main alternative for mild-to-moderate OSA or CPAP-intolerant patients, though it is less effective at reducing the AHI. In a carefully selected patient who is CPAP-intolerant, hypoglossal nerve stimulation (supported by the STAR trial) is an option, but he is above the typical body mass index threshold of 32 to 35, so he would need weight reduction first [4].

CPAP adherence strategy (4 marks): [1]

CPAP is effective only if it is used. Mean objective adherence is around 4 to 5 hours per night, and roughly a third of patients use it poorly or abandon it. The keys to adherence are early and intensive support: correct mask selection and fitting (nasal, oronasal, or nasal-pillows, tried against the patient's anatomy and comfort), heated humidification to reduce nasal dryness, education about the disease and consequences of untreated OSA, proactive management of side-effects (mask leak, nasal congestion, claustrophobia, aerophagia), and structured follow-up in the first weeks. Adherence in the first month predicts long-term use. I would set a shared adherence goal of at least 5 hours per night and arrange objective download of adherence data at each visit. [1]

Evidence regarding cardiovascular outcomes with CPAP — the SAVE trial (5 marks): [1]

The patient should be counselled honestly about cardiovascular benefit. The SAVE trial (McEvoy et al, NEJM 2016) randomised over 2700 patients with moderate-to-severe OSA and established coronary or cerebrovascular disease to CPAP plus usual care versus usual care alone [2]. It found no significant reduction in the primary composite of cardiovascular death, myocardial infarction, stroke, or hospitalisation for unstable angina, heart failure, or transient ischaemic attack (hazard ratio approximately 1.10, not significant). CPAP did improve daytime sleepiness, mood, and quality of life. The key limitation was adherence — mean use was only 3.3 hours per night.

In contrast, the observational study by Marin and colleagues (Lancet 2005) followed men for 10 years and found that untreated severe OSA had higher fatal and non-fatal cardiovascular events, while CPAP-treated patients approached the event rate of healthy controls [3]. The synthesis I would offer: CPAP clearly improves symptoms, sleepiness, blood pressure, and quality of life, and observational data strongly suggest long-term benefit with good adherence, but the single large randomised trial in established disease was negative, partly limited by adherence. He should be motivated by symptom relief and sleepiness reduction, with cardiovascular benefit framed as likely but not proven by randomised data.

Medico-legal obligations regarding his commercial driving licence (6 marks): [1]

As a commercial (heavy vehicle) driver, this is a public-safety issue and a medico-legal duty. The approach: [1]

1. Counsel him immediately that he must cease driving until his OSA is treated and he meets fitness-to-drive criteria. Document this advice and his response. The risk of a crash is approximately 2 to 7 fold higher in untreated OSA and falls towards normal with effective CPAP. [1]

2. Notify the licensing authority. For commercial drivers, the reporting obligation is more stringent than for private drivers. Under the Austroads fitness-to-drive standards, a confirmed diagnosis of OSA in a commercial driver requires effective treatment and demonstration of satisfactory control (with objective CPAP adherence data and resolution of sleepiness, Epworth under 10) before a commercial licence is granted or renewed [1]. I would notify the relevant licensing authority and involve his employer and occupational health.

3. Plan for return to driving. I would reinstate driving once his Epworth is under 10, his CPAP adherence is satisfactory (at least 4 to 5 hours per night documented objectively), and he reports no residual sleepiness at the wheel. I would arrange periodic review. [1]

4. Communicate compassionately but firmly. Frame treatment as the enabler — effective CPAP restores driving fitness, usually within weeks. Document the entire conversation and the notification. This protects both the patient and the physician. [1]

SAQ 2 — CPAP-Intolerant Moderate OSA: Treatment Selection and the Role of Hypoglossal Stimulation (15 marks, 25 minutes)

Prompt: A 48-year-old woman with moderate OSA (AHI 22) cannot tolerate CPAP despite intensive support and multiple mask trials. Her body mass index is 30, and drug-induced sleep endoscopy shows anteroposterior palatal collapse without concentric collapse. Outline your management approach, including the evidence base for the alternatives and the selection criteria for hypoglossal nerve stimulation. [1]

Model Answer

Stepwise approach to the CPAP-intolerant patient (4 marks): [1]

For a patient with moderate OSA who is genuinely CPAP-intolerant despite intensive support, the alternatives, in order of evidence, are: a mandibular advancement splint (oral appliance) as the next-line treatment, and — for a carefully selected subset — hypoglossal nerve stimulation. Surgery (uvulopalatopharyngoplasty) has limited and inconsistent evidence and is not first-line. I would also revisit lifestyle measures (weight loss to a 10 percent target can reduce the AHI by approximately 50 percent, potentially moving her from moderate to mild), positional therapy, and EPAP valves as adjuncts. [1]

Mandibular advancement splint (3 marks): [1]

A mandibular advancement splint holds the mandible forward during sleep, pulling the tongue base and soft palate anteriorly to enlarge the pharyngeal airway. It is less effective than CPAP at reducing the AHI on average, but adherence is often better, making it the main alternative for CPAP-intolerant patients. It requires dental assessment and may cause temporomandibular joint discomfort or dental movement. Treatment response should be confirmed with a repeat sleep study with the device in place. [1]

Hypoglossal nerve stimulation — the STAR trial and selection criteria (5 marks): [1]

Hypoglossal (upper airway) nerve stimulation delivers synchronised stimulation to the hypoglossal nerve on inspiration, protruding the tongue and opening the airway during sleep. The pivotal STAR trial (Strollo et al, NEJM 2014) was a multicentre prospective study of patients with moderate-to-severe OSA who had failed or could not tolerate CPAP, showing a 68 percent median reduction in AHI (from 29.3 to 9.0) at 12 months with durable benefit at 5 years [4].

Stimulation is indicated for a defined and carefully selected group: adults with moderate-to-severe OSA (AHI 15 to 65) who are CPAP-intolerant, with a body mass index under 32 to 35, and without complete concentric airway collapse at the palate on drug-induced sleep endoscopy. This patient meets all these criteria — her AHI of 22 is within range, her body mass index of 30 is under the threshold, and her sleep endoscopy shows anteroposterior (not concentric) collapse. She is therefore a suitable candidate, and I would refer her to a specialist centre for assessment. [1]

Shared decision-making and follow-up (3 marks): [1]

I would discuss the options with her honestly — an oral appliance first (less invasive, less effective on average, but reversible and often better tolerated), and hypoglossal stimulation if the appliance is inadequate or not tolerated. I would confirm treatment response with a repeat sleep study on whichever therapy she chooses, monitor her symptoms with the Epworth Sleepiness Scale, and ensure her cardiovascular risk factors are addressed. The goal is symptom relief (sleepiness) and AHI reduction, with the understanding that adherence is the determinant of real-world benefit. [1]