Evaluating Sleep Apnea
When we're awake, it's easy for the muscles that help us breathe to maintain shape and stay open. However at night, the muscles become relaxed, and for some can lead to disruptive sleep disorders such as Sleep Apnea or Obstructive Sleep Apnea. We've shared how sleep apnea develops, but here's how doctors tell if you do have apnea, or just simple snoring.
If the pharynx collapses, and a person stops breathing for 10 seconds, it's considered apnea. If airflow decreases by 30 percent and also shows a drop in blood oxygen, it's known as hypopnea. But less than 5 events of hypopnea and apnea together is considered normal on the Apnea Hypopnea Index. Also, those who have apnea are often woken up by the body's response to overcome airflow restriction, known as Respiratory Effort Related Arousals (RERA's). This is frequently described by partners as an "explosive snore followed by a breath while awakened."
Making the DiagnosisClearly, it's not very difficult to obtain abnormal results in a sleep study. So it's not prudent to make a diagnosis of Obstructive Sleep Apnea and treat it, solely based on an abnormal sleep study. Unfortunately however, many physicians do. In fact, requirements by government agencies state that before ordering a test to confirm OSA diagnosis, a full history and exam must be performed, and there must be "reasonable clinical pre-test probability" of a sleep breathing disorder.** A full history and exam should include:**
Taking a history of sleep-wake schedule habits
Examination of the airway anatomy
Evaluation of patient's body mass index
Evaluating the consequences of disturbed sleep
Primarily, these tests are often often done due to the common complain of abnormal daytime somnolence, or desire to sleep. But there are standardized tests to help measure this. In my practice I use the Epworth Sleepiness Score, which indicates the severity of daytime sleepiness, and the Berlin Question, which predicts the likelihood of sleep apnea.
Even if sleep apnea has been diagnosed and a decision is made to treat the condition with a CPAP machine based on results of the sleep study, it doesn't end there. There must be a follow-up appointment with the physician so that he or she can read the data card of the machine, and measure usage, events and any leaks. The physician can also make any adjustments to pressure settings. This process is ongoing, so it's best to work with a physician who is familiar with the diagnosis and treatment of sleep disorders.
If you think this is complicated, it is only the beginning. What I've described applies to an otherwise healthy patient. MAtters are further complicated if a patient has heart disease, hypertension, or atrial fibrillation and COPD (known as overlap syndrome). There's also a different form of apnea called Central Sleep Apnea, where there is no obstruction, but the brain still does not send the signal to breathe. In many cases with heart disease, and for those taking a certain medication that affects sleep, there is usually a combination of both forms of apnea.
All of which deserve an article of their own.