Diagnosis and management of obstructive sleep apnoea in adults

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Hi, and welcome to this Australian Prescriber podcast. I'm Dr Justin Coleman, a GP who works in Aboriginal health in Inala in Brisbane. I sometimes worry my podcasts will put people to sleep, but you can stay awake for this one because you might learn something you didn't know about obstructive sleep apnoea in adults.

I have with me Darren Mansfield who wrote an article in Australian Prescriber. Darren is the Director of the Epworth Sleep Centre and Adjunct Associate Professor at the Faculty of Medicine, Nursing and Health Sciences at Monash University. Welcome to the podcast, Darren.

Hello, Justin.

It's great to have you here. Obstructive sleep apnoea is something which was only emerging even as a diagnosis really when I graduated medical school, but it has become increasingly prevalent, probably not because it's more common in society, although with obesity increasing, I guess maybe it is. But it's probably more, I think, because we're just looking for it more and diagnosing it more. Is that the main cause of the increase?

That's correct. One of the key determinants of the current prevalence is greater awareness, but also we have much larger-scale trials looking at community populations and screening for sleep apnoea. We're now estimating something in the order of one billion people worldwide would have some degree of sleep apnoea.

The sound of a billion snorers is something we can all contemplate. The first thing I wanted to ask you about was screening. Who do we screen and how do we screen for sleep apnoea?

It's a very important question and the consensus opinion is that, despite such a high prevalence, routine population screening is probably not required, and in fact, we are still better to target higher-risk populations for screening. In primary care, there will be those that will present with symptoms, and clearly screening tools can be helpful in that group.

Overweight and obese people have a much higher prevalence of sleep apnoea. A BMI of more than 35, we would expect 80% of those people would have clinically significant sleep disordered breathing. Hypertensive populations, particularly those with refractory or resistant hypertension, are strongly linked to sleep apnoea. There's certainly some evidence to suggest that blood pressure is better managed if sleep apnoea is indeed diagnosed and treated in that group.

There's other higher-risk populations where I think the consideration of sleep apnoea ought to come into the clinical assessment – those with stroke, cardiovascular disease. Even among women, I think we forget that sleep apnoea is prevalent, not as prevalent as men, and therefore, in some instances that can lead it to be overlooked. But polycystic ovarian syndrome, which is a common condition that may affect young women, I think it's important to ask them do they snore, or even consider putting them through a screening questionnaire.

Just a question which has occurred to me and I'm curious about, for thin people, people of normal body habitus who have sleep apnoea, do you usually find it is actually a physical anatomical airways anomaly or that there tends to be some other cause?

We still see lean people with significant sleep apnoea. Twenty-five per cent of sleep apnoea will be among the leaner groups. There still can be anatomical factors like retrognathia, that short jaw for example, which diminishes that posterior airway space, or looking inside the airway, you may see tonsillar hypertrophy. What you can't see is lingual tonsils. That needs an endoscopy to assess those, but they can really crowd up that posterior airway space.

Upper airway muscle tone is, again, something that we can't assess clinically but rather through physiological testing we can identify this. Arousability and respiratory control mechanisms can all feed into the propensity towards sleep apnoea.

Now, these are predominantly laboratory research investigation tools at this stage. They're not broadly in clinical practice and routine sleep studies do not identify these factors, but they do explain at least a contribution to sleep apnoea across all groups, not just the leaner ones. Indeed, in some instances where obese people lose significant weight and their sleep apnoea may persist, which suggests that there may be other physiological contributors that may be driving the ongoing sleep apnoea.

Let's talk about the history. Most health practitioners these days are fairly familiar with asking about the interrupted sleep, the daytime somnolence, and you wake up with a dry throat and feeling that you haven't had a good night's sleep, and maybe you have poor concentration. It is important, you pointed out in the article, to ask questions of witnesses as well. I assume here you're largely talking about someone who shares the same bed. What sorts of things do we ask those people?

Witness assessments are really powerful. My own experience would suggest that when we take a direct history from a patient and then the partner who was parking the car comes in a bit late for the consultation and provides information that practically contradicts everything I've just heard.

We know witness assessments significantly influence our overall impression, so that can be, of course, severity of snoring, the extent to which that it's disruptive to the partner, and that actually is an important consideration in the treatment discussion. Do partners move into another room and how frequently? Don't just ask about apnoeas per se. Those little gasps and snorts which are the terminations that's picked up by the partner, so definitely ask about those as well.

Moving on to examination, just specifically for sleep apnoea, something I must say I rarely do is a neck circumference. The other thing I wanted to ask about is you mentioned retrognathia, which I assume means the bottom jaw is receded or posterior compared to the top jaw. I'm imagining we look at the teeth position. How do we measure neck circumference and retrognathia?

The neck circumference, if you have a tape measure handy, it is a good part of the assessment to do and one of the screening tools that we use, the STOP-BANG questionnaire, specifically asks you to record the neck circumference, and a neck circumference greater than 40 cm is a predictor of sleep apnoea.

Retrognathia, I don't think it's something that we can formally measure. It's really just the impression of that receding jaw that we can directly take in by just looking at from a lateral position. Teeth positioning, the upper teeth sitting more forward than the bottom teeth, is something else to assess and also is a predictor that that posterior airway space might be narrowed.

Looking at investigations now, and clearly the gold standard is going and getting a sleep study in the lab. A lot of those have moved now to be home-based testing. Is there much difference between the two?

In general, no. Home-based tests can be more satisfactory to the patient themselves, sleeping in their own home, in their own bed with their own pillow might suit them. The laboratory setting has some small advantage in that signal quality is perhaps better maintained across the night because there is a staff member in attendance, and so the failure rate from a home test, which is below 5%, occurs much less frequently in a laboratory setting.

The laboratory does have the opportunity to video the patient. We do find that videoing the body position is more reliable than body position sensors. There may be some instances as a clinician if you are really thinking body repositioning strategies is your preferred option, you may choose to do a laboratory test for that reason. Otherwise, I tend to use home-based tests predominantly these days because they are, in general, a good and convenient option for the patient. Just bearing in mind, and I do warn them that perhaps one in 30 instances where we just find, due to signal quality, we're repeating the test. Doesn't happen often, but if we warn them it can happen in advance, they're a little less disgruntled if they're repeating the test.

The other instance is geography, so if patients have to travel a distance, then sometimes travelling to a laboratory is easier for them than travelling to pick up sleep equipment, and then driving a long distance back.

One other consideration is the application of the sleep equipment and I do think patients prefer a facility where the staff can apply the signals and the wires to them rather than a self-application. That is achievable and the patients do, in general, pull it off, but they're nearly always apprehensive that they haven't done it well and that the test will fail. On average, they are, I think, more comforted by staff applying the wires and the signals to them for the home test.

Moving on now to treatment, the main treatment we're going to talk about is the positive airway pressure, which I always think of as CPAP, but of course increasingly common now is APAP. Could you just briefly explain the difference and the advantage?

Historically, we perform CPAP titration studies in a laboratory and establish the optimal CPAP pressure and fix the CPAP device to that pressure. That would be the pressure that would cover all instances in which sleep apnoea might occur across a night. Therefore, it has to be a little bit higher to cover supine sleep in which the sleep apnoea may be a little worse or REM sleep similarly.

Over the last 15 or more years now, we've had auto-titrating devices. These are smart devices that work by identifying vibration in air flow to suggest imminent upper airway closure, or for that matter, a hypopnea or an apnoea. When it detects that, it will increase the pressure accordingly until we have normal ventilation. After periods of time of normal ventilation, these devices are always trying to lower the pressure if possible. They, therefore, will vary the pressure up and down across the night according to prevailing levels of sleep apnoea. On average, the pressure can be a little bit lower with these devices and some patients do find that is, therefore, more tolerable.

Take some care with that. Some patients will find that they wake with more rapid pressure increases, and then by being awake at the higher pressure level, they may find it uncomfortable. When we sense that, we may either cap the top pressure or go back to a fixed-pressure device. So there still is a role for fixed-pressure devices. Bear in mind that any auto-titrating device has a fixed-pressure option as well, so you don't have to buy a different pump if you do choose to go back to a fixed level.

A thing of note, which I didn't know until I read your article, was that the CPAP or APAP doesn't have to be necessarily all night. You get most of the advantages with 6 hours of use, and in fact, the minimum suggested is 4 hours of use at night.

Moving on, because there's another mention that almost half the patients who start PAP therapy can't tolerate long-term use, so we might need to use alternatives. I was surprised at that number. Has that always been the case?

Yeah. I think that's always been the case, and interestingly, it has not got a lot better over the last 20 years. With more sophisticated devices, quieter devices, and probably costs not significantly increasing over that time period, we're still seeing somewhere in the order of 40 to 50% of patients are struggling with long-term adherence, and therefore, clearly we need to explore alternatives.

I wouldn't call it an alternative, but it's something all of us would always be thinking of with someone with a very high BMI, of course, is weight loss. And so, a 10% reduction in weight has been shown to cause a 26% decrease in OSA symptoms, which is impressive and certainly something we do frequently think about, along with looking at trying to minimise alcohol intake and also having a medications review, particularly rationalising those medications that might worsen the problem.

But besides that sort of more general health review of the person, there are some specific things. First of all, positional therapy. Now, I used to write a GP handy hints column and I remember publishing a few of these over the years. The most dramatic one being put a tennis ball in a sock and pin the sock to the back of your pyjamas, which makes it very uncomfortable to lie on your back. I assume you have something slightly more sophisticated than that these days.

Yes, yes. That's certainly the old-fashioned way of doing things. More recently, other ways of achieving the same result include semi-rigid cushions that can be strapped to the back. They come under the broad category of bumper belts, and they're able to be Googled and purchased online. They're somewhere between $150 and $250. They tend to prop individuals more in the side-on position rather than allow them to roll to their back.

There are body positioning sensor devices that people can wear either as a strap around their neck or their chest. As they move into the supine position, they will buzz or vibrate and that arousal response will tip people back into the side-on position. Trials suggest something in the order of 60 to 70% longer-term adherence. I might suggest that in the real-world clinical practice, it's a little lower than that, but I think it's an underrated option.

I certainly suggest body repositioning strategies for people who have supine-predominant sleep apnoea who really have either struggled with CPAP, or aren't prepared to trial CPAP, because it is a genuinely useful option for these people as long as they stick at it.

Thank you. Another form of device used [are] things you put in your mouth or do to your oral airways.

Oral appliances advance the bottom jaw to open that posterior airway space. It's efficacious for mild and moderate sleep apnoea; it certainly can reduce the severity of more severe sleep apnoea. There’re many devices. You can buy them online. You can go to chemists. Some of the simpler ones are a boil-and-bite option. Just bear in mind that sometimes the boil-and-bite options don't allow progressive advancement of the jaw over time and the jaw is pulled to the maximum distance from night one and that can actually cause a bit of discomfort.

I think a custom-fit device that is adjustable generally has better outcomes. That generally requires an assessment from dentists, and a custom-fit device produced by dentists is not cheap. However, they're not significantly more expensive than a CPAP machine itself, so we may be looking somewhere between $1500 and $2500 for a custom-fit dental appliance. I do recommend it is worth the money because you get the ongoing surveillance of teeth positioning and it [teeth shift] does occur not infrequently with long-term use, although rarely requires anything truly corrective.

We're almost out of time. I thought we might touch on surgical options. One thing not mentioned in your article is bariatric surgery. I would imagine that post bariatric surgery you would expect a certain percentage of improvement in sleep apnoea, and then there's more specific upper airway surgery.

Yes. Well, if we take weight loss first, there are a number of trials that have looked at levels of sleep apnoea reduction with old-fashioned approaches with diet and exercise, and they're mostly disappointing. We've certainly seen very significant increases in weight loss through bariatric surgery which have dropped sleep apnoea severity markedly.

A very exciting innovation is the GLP-1 inhibitor class of medications where we are achieving weight loss, on average sometimes 16 to 18 kg, and that does have appreciable effects on sleep apnoea severity. It is early days with these medications and there is still some hesitancy in their use, and clearly some significant limitations in supply in Australia as well as cost, but it is one that I would suggest as a group we are watching very closely as to the role of these medications moving forward.

Upper airway surgery requires very careful patient selection and there's a few options that can be considered. Tonsillectomy for large grade 3, grade 4 tonsils has excellent success for a lot of sleep apnoea patients. Resecting or modifying the soft palate and the uvula can have a role in reducing sleep apnoea, perhaps more in the milder cases, perhaps extending into moderate sleep apnoea for highly selected people, and also can have a role in snoring reduction.

There are more complicated surgeries including tongue base resection, which have some evidence behind them in terms of its efficacy, again in highly selected patients. Indeed, we see there is a role for surgery, but I do suggest that we present many of the other alternatives first. If, after working through that list, we're left with serious discussions around surgical options, then they may well be referred for an assessment.

Well, Darren Mansfield, thank you so much for joining us today, and interested listeners can read the article in Australian Prescriber. Thanks very much for your time.

Thank you very much, Justin.

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Darren Mansfield is a member of the Sleep Health Foundation board. He has received speaker honoraria from Somnomed, a producer of mandibular advancement splints.