So your spouse tells you about your nighttime gasping, and you're waking up with headaches and dry mouth and your blood pressure has gone up. You realize, hmmm, it's time to find out if I have sleep apnea or some other related sleep breathing issue.What can you expect to experience at the doctor's office when you go in?
Basics
The doctor will collect your health history, collect your vital signs and ask you about your chief complaint. They will also compute your body mass index, measure the circumference of your neck and maybe even the circumference of your waistline. These numbers together can provide good objective information to indicate a likelihood for sleep disordered breathing.
Questionnaires
Be prepared to fill out at least one, and maybe several, forms. Patient questionnaires are a common screening tool for determining whether a diagnostic test is necessary to determine what's causing your problems. The most common questionnaires include the Epworth Sleepiness Scale, the STOP BANG questionnaire and the Berlin questionnaire, but there may be others. The intent in having you answer these questions is to determine whether you have a higher likelihood or risk for a sleep breathing disorder. They are not, in and of themselves, diagnostic tools, and doctors understand that they are generally subjective and not completely accurate, as patients may or may not answer them accurately (either because they want to hide symptoms or because they don't realize the fatigue they suffer is not normal). Still, they help to screen patients.
Overnight pulse oximetry
If the doctor, after assessing you with basic measurements, collection of history and your own questionnaire responses, feels you have the risk factors associated with a sleep breathing disorder, they may send you home with a little device called a pulse oximeter. You may already be familiar with this little mechanism: a clothespin-style clip which shows a red light when powered up and placed on your fingertip. The pulse oximeter is designed to measure trends in blood oxygenation overnight as you sleep. You turn on the device, clip it to your fingertip so the red light comes on, and go to bed, wearing the device all night. It doesn't hurt and most people forget they have it on while they sleep. Data is collected on a memory chip inside the pulse oximeter and when you return it to the doctor the next day, they can download the information and learn what a typical overnight for you looks like from the point of view of your blood oxygen. If levels dip frequently below a set percentage, that could be an indication that you have a sleep breathing disorder.
Home sleep testing
Also known in the industry as HST or portable sleep monitors, these mini sleep studies include the aforementioned pulse oximeter, two belts used to measure respiration (breathing patterns) that go around your chest and your waist, and an airflow measuring device you wear in your nose (it looks like an oxygen cannula but has sensors built into it that measure the flow for both inhale and exhale).
You may be sent home with this kind of test in lieu of the overnight pulse oximeter, or you may follow a simple overnight oximetry test with one of these. Insurance companies often demand an overnight portable sleep test like this to confirm a doctor's suspicions that you might have a sleep breathing disorder. The reason is simple: overnight sleep tests in the sleep lab are very expensive and insurance companies want to find ways to eliminate unnecessary tests. HSTs aren't particularly accurate for diagnosing sleep breathing disorders; they are better used as a screening tool to rule in or rule out the condition. Keep in mind that if you have other health conditions (i.e. pulmonary disease, neuromuscular disease, congestive heart failure, other confirmed sleep disorders), you will not qualify for a home test and will be asked, if needed, to attend an overnight study in the lab setting.
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| Image courtesy National Heart, Lung and Blood Institute |
You may find that after overnight oximetry and/or HST, your doctor still wants you to come in for an overnight stay. The overnight polysomnogram (NPSG) is considered the gold standard for assessing and diagnosing sleep breathing disorders (as well as other sleep issues not related to sleep). You can find a comprehensive description of this kind of testing here. This is the test that requires you stay at the lab, be "hooked up" to numerous sensors, and have your data recorded as you sleep. It measures brain activity to confirm sleep stages (or lack thereof), muscle activity, respiratory pausing, eye movement (which corresponds with sleep staging), snoring and other elements distinct to the sleeping process that are useful in making a diagnosis.
Further overnight testing and daytime testing
Once you have an NPSG, you may be asked to return for a second visit; this is because you may have qualified for a sleep breathing disorder diagnosis and the second visit may be the test that confirms your best treatment protocol. Note: Sometimes both diagnostic and therapeutic protocols take place during the same night; these are determined specifically by your performance during the test or by other factors the doctor may be interested in measuring. Sometimes you will also be asked to stay for a series of daytime nap tests to rule out other sleep disorders as well.
Perspective
The important thing with all overnight tests is to recognize that, as each human being is a truly unique individual, so is every sleep study going to be unique to that patient. What happens for one patient may not be the same pathway for another. This is the nature of the testing and not a questionable practice on the part of the doctor.
If you are anxious about attending an overnight test in the sleep lab, please share this information with your physician; you are usually able to bring comfort items to help you relax or use a sleep aid if you think you will have trouble falling asleep. Labs usually carry white noise machines to help with patients who are light sleepers. The protocol for your lab will be shared with you well in advance of your study and the details of what to do will be outlined there so you will know what to bring, what to leave at home, what to wear, what meds to take and so forth.
For more frequently asked questions about overnight sleep studies, click here.
