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Sleep disordered breathing includes a group of disorders, such as obstructive and central sleep apnea, that are characterized by repeated arousals from sleep as a result of a cessation in breathing, causing highly fragmented and poor quality sleep. Many studies point to a strong link between sleep disordered breathing (SDB) and a number of disorders, particularly cardiovascular disease. Several other studies are finding that adverse surgical outcomes are more frequent in patients with sleep apnea, as both anesthesia and surgery exacerbate airway instability and affect homeostasis in that patient population.

Dr. Nancy Foldvary from Cleveland Clinic Foundation suggests that patients with sleep apnea may be at increased risk for postoperative complications with a greater need for intensive monitoring. Since SDB is a complicating factor in many surgeries, the ability to conveniently conduct a sleep study in those settings can improve the peri-operative management of care, particularly for bariatric and cardiac surgery patients who have high prevalence of obstructive sleep apnea (OSA) (Another potential application for wireless PSG is to diagnose those inpatients with cardiovascular disease who are also suspected of having OSA).

Dr. Nancy Collop with John Hopkins University summarizes that there is an urgent need to improve the diagnosis of sleep disordered breathing in surgical patients in order to avoid complications intraoperatively and postoperatively.

This post draws from the opinions of experts featured in the following news article: CleveMed receives $2.3 million in NIH funding for inpatient diagnosis of sleep disorders in cardiovascular surgery patients

When opening a new sleep lab, the cost of hard-wiring the rooms can be a significant portion of the cost of the installation. The installation team must work with hospital technical staff, often for a day or even two days before systems are up and running. Cabling must be run and tested.

Wireless Advantages:

On the other hand, wireless devices can transmit data through multiple walls without any cables running through ceiling tiles. There are often less components, meaning easier setup and lower risk of individual component failure. Setups outside of the lab become more feasible. For example, mobile diagnostic studies in hotels, long term care facilities or nursing homes mean that a comprehensive sleep diagnostic service can come to the patient instead of the patient having to come to the lab for a PSG. Hospital networks, wireless or intranets are used to transfer sleep studies from the bedside to the sleep lab. Technicians can monitor and respond to problems, yet the patient is still under the immediate supervision of skilled nurses.

Wireless Not Flawless:

But, anyone who has ever lost a connection on a cell phone knows that wireless technology is not yet flawless. If a PSG study is interrupted several times through the night, since typically the amount of PSG data being transmitted is so large, even brief lapses can disrupt acquisition, annoy sleep techs and may affect data interpretation.

Workarounds:

Wireless systems work by transmitting data via electromagnetic waves at a defined frequency. With so much congestion in the 2.4 GHz band (the most commonly used, from Wireless Local Area Network to microwave ovens), the probability of losing data due to radio frequency interference increases. In order to enhance their immunity to interference, most wireless devices operate in a pseudo-random fashion, a strategy known as “hopping“. Because this signal is not stationary, the approach works well for small and intermittent transmissions, like browsing the internet. Sleep studies however, have large data files that are continuously streaming for hours, which make the process of data recovery more difficult if not impossible. One potential way to mitigate this problem is to simultaneously store the PSG data in memory inside the bed-side unit and use the transmitted data only for basic patient status check and to confirm electrode connections.

Our next post:
Questions that you should definitely be asking your potential equipment supplier if your sleep lab is considering going wireless.

This post draws on the experience of several experts at CleveMed and is an adaptation from “Wireless Polysomnography” as seen in Sleep Diagnosis and Therapy, June⁄ July 2006.