What exactly is a sleep study?

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'Sleep study' is a pretty wide ranging term. There are different types of study available to investigate any problems you have when you are asleep. The depth of investigation, and the accuracy and usefulness of the results, ranges from simple screening for instance using an app on your phone, through to spending a night in a bed in a sleep clinic, where everything that it is possible to record while you sleep is recorded.

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Awareness of sleep disorders has grown over the last few years, driven to a large degree by increased media attention improving awareness of the problem. This is hugely beneficial to individuals and to wider society as we live in a time where we have the ability to take more interest and become more proactive with regard to our health and wellbeing.

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Routine sleep studies have largely moved from specialist sleep laboratories and into the home, driven to a large extent by demand far exceeding sleep laboratory capacity. In reality most people don't need the very specialist additional measurements that are made in a sleep laboratory, and these resources are used where they are most needed clinically. Screening using a simple device - or a smartphone - does not really answer the question. This type of screening often produces more questions than answers, and usually leads to doing a sleep study anyway.

 

The answer is polygraphy - a multi-channel recording of the essential parameters, and this is precisely what we provide. Using the same equipment at home ensures quality and integrity of the data, and a report that a sleep specialist can work with. Polygraphy is now the standard used for most sleep studies.​

 

 

Diagnostic or Screening?

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As awareness of OSA and other sleep condition has grown, there has been a parallel growth in diagnostic options. Many of these options are smartphone based, and impressively claim to be as accurate as an old fashioned sleep study. While it can be interesting to explore these apps, results obtained should be viewed with caution. Smartphones are indeed pretty smart, and software is getting better all the time, but if you don't measure something, can you really report on it? Only by making a lot of assumptions, and when the 'data' generated by these assumptions is then used to feed into further assumptions that generate the next level of 'data' things can quickly lose all meaning.

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To properly investigate OSA you must as a minimum measure these parameters:

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• Airflow in and out of the mouth and nose

• Snoring

• Oximetry - continuous monitoring of oxygen levels in the blood

• Breathing effort - preferably both the thoracic (chest) and abdominal (tummy)

• Body position

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Additional parameters such as actigraphy can be helpful in addition to the core measurements.

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Continuous recording of these signals detects apnoeas and hypopnoeas (no or reduced airflow) and differentiates into obstructive (effort but no flow), central (no effort or flow), and mixed events (initially no effort or flow, then effort but no flow). Drops in oxygen levels associated with the pauses in breathing are clearly seen, and will also indicate the likelihood of other conditions associated with prolonged low levels of oxygen such as OHS - Obesity Hypoventilation Syndrome. Recording snoring will indicate if the problem is just snoring, or if it is OSA. Recording body position can identify a particular type of OSA - POSA or positional OSA.

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Devices used for sleep screening - smartphone based or otherwise - that do not accurately measure and record these physiological parameters are providing data derived from some other measurement. This is generally achieved by extrapolating or inferring from the limited measurements made. If you decide you should have a sleep study, the least you should expect from the study is that it does not give you inaccurate test results because these most basic parameters are not even recorded during the study. A video is available demonstrating the setting up of the SOMNOTouch Resp in preparation for a sleep study.