How to Interpret the Results of a Sleep Study for an ASC Nurse

To continue our series on sleep apnea management, let’s discuss what happens after a patient has been sent to a sleep lab. What do the results mean—both for the patient and for you?

Treating patients with sleep apnea

Sleep apnea affects over one-quarter of men between the ages of 30-70. It is highly likely that, at one point or another, you will refer patients to diagnostic testing for sleep apnea. When they return to you with the results, how can you help them understand what it all means?

A typical sleep study will include five key areas of feedback: sleep quantity, sleep efficiency, sleep stages, body position, and respiratory patterns.

Sleep quantity

This number is often reported as total sleep time (TST). The number of hours may be contrary to how a patient feels they slept, as sleep apnea can make a person feel drowsy and restless even after a full night’s sleep.

Sleep efficiency

Sleep efficiency is a measurement that looks at how long the study ran versus how much a person slept. For example, recording time could have run for eight hours, but the patient only slept for six. This section also looks at sleep onset latency, which refers to how long it takes a person to fall asleep.

Sleep stages

Most people have some very basic knowledge of the sleep stages. The sleep cycle occurs in four phases: light, fairly light, deep sleep, and rapid eye movement (REM) sleep. The fairly light stage should account for about half of a person’s TST, with deep sleep accounting for only about 20%.

Body position

The results will likely indicate how much time the patient spent in different sleep positions. This information matters because many patients experience more severe apnea when sleeping on their backs. The study may also show how many episodes of desaturation occurred in certain sleeping positions.

Oxygen saturation

Sleep studies will also measure how many times a person stirs or awakens throughout the night. The arousal index on a sleep study refers to the number of times a person has awakened per hour. For patients with sleep apnea, episodes of desaturation can be the culprit for waking up multiple times throughout the night. The study also records how many of these episodes of airway obstruction occur per hour; this is called the respiratory disturbance index (RDI). An RDI from 5-14 is considered mild sleep disturbance; 15-30 is moderate; and any number above 30 is severe. The desaturation is also recorded, and anything under 79 is considered a severe desaturation.

What does it all mean?

Based on the results of the sleep study, your patient may have been preliminarily diagnosed with sleep apnea. They may also have been instructed to being using a continuous positive airway pressure (CPAP) machine.

What does this mean for your surgery center? Prior to surgery, patients need to understand the results of their sleep study and understand their risks in surgery. They will need to bring their CPAP machine on the day of surgery. The surgical team will need to be prepared with the necessary equipment and maneuvers for keeping patients with sleep apnea safe in surgery. Read more here about practical considerations for sleep apnea management during surgery.

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