Simple home sleep studies

A couple of weeks ago I discussed the new recommendations to Medicare with regard to home sleep studies.

There are very simple techniques available for the evaluation of breathing overnight in the home environment. One of these is the Apnealink, a device from ResMed which measures only nasal air flow and oxygen saturations (pulse oximetry) overnight.

There are several reasons why such devices are not very widely used in Australia yet. One reason is that there is no medicare payment for their use - in part because the evidence as to where they should be used is still lacking a little. Apnealink devices are mostly used in the environment where CPAP machines are sold - which most of us agree is a bit of a conflict of interest. Funding for the use of the Apnealink device in that situation often comes from the subsequent sale of CPAP machines.

However, there is increasing evidence that such devices are useful, and I expect they will be widely used in the future.

One study, published in Respirology journal this month, demonstrates their potential utility in one particular situation. This study, which included researchers from Sydney, Adelaide and Shanghai, used Apnealink and a formal home sleep study device in a population with high cardiovascular risk. That is, from a community register, patients with a either a previous cardiovascular event, or two of hypertension, age over 55, cigarette smoking (current), diabetes, and BMI over 27 were selected. The average BMI ended up being under 27 (ie only just overweight). Of 257 eligible subjects, 190 completed sleep studies (on one night only, both Apnealink and full polysomnography) and only 143 studies were sufficiently good to be analysed. 62 subjects ended up having at least moderate OSA (ie an apnoea hypopnoea index of at least 30 events per hour).

Apnealink had high diagnostic sensitivity and specificity for moderate to severe OSA.

Now, as I tell patients, there are always three possible reasons for doing something about obstructive sleep apnoea. The first reason we treat OSA is that it may be clinically significant; that is, a patient may be very sleepy in the daytime. In that situation we treat OSA to make the sufferer feel better.

The second reason we might treat OSA is that it may be disturbing the sufferer's bed partner - usually their wife, in our context. So we often treat OSA to help the partner feel better!

Finally, with the increasing evidence that OSA is an independent risk factor for cardiovascular disease, we treat severe OSA to reduce future risk of heart disease.

There are huge numbers of patients with heart disease. If we are going to take seriously the challenge of screening patients at risk of heart disease routinely for obstructive sleep apneoa, then we are going to need to have a much simpler diagnostic test to use routinely - even if only to filter out the patients who have no significant OSA, and not clog up our sleep labs with those patients. Apnealink probably fits the bill

Andrew

Apnealink picture uploaded from ResMed website