Obstructive sleep apnea (OSA) occurs when the upper airway collapses during sleep and blocks normal airflow. This collapse occurs when the muscles supporting the soft tissue in the throat relax, temporarily constricting the airway (often, bed partners or other family members will notice the stoppages in breathing). The obstruction of a person’s breathing during sleep can result in frequent arousals, reduced sleep time and less deep sleep, and may also significantly lower blood oxygen levels during sleep. Those effects can, in turn, contribute to feelings of not having slept well, daytime fatigue and tiredness, low energy levels, and possibly severe daytime sleepiness. Loud snoring, morning dry mouth and headaches also may be present in people with OSA.
A lack of quality sleep attributable to untreated OSA also can have negative effects on concentration, memory, and job and school performance, and can increase a person’s risk of accidents—including motor vehicle accidents. Studies indicate that long-term OSA, particularly if moderate or severe, increases a person’s risk of developing hypertension, heart disease, atrial fibrillation and stroke.
A Common Problem
Recent studies suggest that up to 50% of men and up to 25% of women may have OSA. The risk of having the disorder increases with age and is especially high in overweight and obese individuals. More men than women have OSA, and risk of OSA is higher in people with other medical conditions such as hypertension, heart disease, diabetes, congestive heart failure and chronic kidney disease.
Diagnosing OSA and Other Sleep Disorders in the Sleep Lab
Definitive diagnosis of OSA requires a sleep study to document significant reductions in airflow, accompanied by awakenings and/or decreases in blood oxygen levels. The gold-standard test is a monitored sleep study performed in a certified sleep lab. This is most often done overnight, although daytime assessments can be carried out if the patient normally sleeps during the day.
The in-lab study provides the most comprehensive assessment of sleep, including, at a minimum, measurement of brain wave activity with an electroencephalogram (EEG), as well as monitoring of eye movements. These measurements allow the sleep physician to confirm the onset of sleep and its duration, and to monitor the patient’s stage of sleep, allowing the physician to distinguish deep sleep from lighter stages of sleep. In-lab studies also provide measurements of airflow, respiratory effort, blood oxygen levels, heart rate and rhythm, body position, assessment of arm and leg movements during sleep, and video monitoring. This extensive observation allows not only for a definitive diagnosis of OSA, but also for recognition of other unrelated sleep disorders that may be present, including grinding or clenching the teeth, leg kicking, sleep-related seizures, the inappropriate acting out of dreams, and other less common sleep disorders.
OSA is diagnosed and its severity is determined based on the number of times the patient’s breathing is obstructed per hour of sleep. Obstructive breathing events are classified either as apneas (a complete absence of airflow for at least 10 seconds) or hypopneas (a reduction in airflow for at least 10 seconds, accompanied by a significant drop in blood oxygen level and/or an arousal from sleep).
Diagnosing OSA with a Home Sleep Study
Home sleep studies offer an alternative to in-lab studies for diagnosing OSA. Typically less comprehensive than an in-lab study, a home study is limited to testing for the presence or absence of significant OSA. Although the number of parameters measured does vary among different home monitoring systems, most units are limited to measuring airflow, respiratory effort, blood oxygen levels and heart rate. Some home testing systems do include channels for measuring body position and estimating the degree of snoring. However, home testing typically does not provide for recording the patient’s EEG, which precludes being able to determine sleep onset and stage of sleep. In addition, home testing typically provides no assessment of the patient’s limb movements—especially leg kicking.
Comparing Lab-Based and Home Sleep Studies
With its greater diagnostic capability, in-lab sleep monitoring is more expensive than home sleep studies, as well as less convenient, since patients are required to spend the night in a sleep lab. In-lab studies also are more cumbersome, since many more electrodes are attached to the patient’s body, and potentially less comfortable for patients who may have trouble sleeping in a strange bed away from home.
In addition to being less costly, home sleep testing enables physicians to assess patients in their normal sleeping environment, which may allow for a more typical night of sleep. Home testing is also more convenient for patients who may have trouble leaving their home. However, compared to in-lab assessments, home testing is limited to evaluation for OSA. If testing for other sleep disorders is required, a home study will not suffice.
During in-lab studies, a sleep technician monitors the sleep study and can recognize and correct problems with data collection during the test. Since home testing is not monitored by a sleep technician, it comes with a higher incidence of unsuccessful data collection, causing the need for home studies to be repeated more frequently than in-lab studies.
An important limitation of home sleep testing is its inability to document when the patient is experiencing true sleep. This is important because the severity of a patient’s OSA is based on the number of obstructive respiratory events occurring per hour. If the patient is awake during some of the testing period, the study will underestimate the severity of OSA, since people typically do not have obstructive respiratory events when they are awake. Consequently, home sleep assessments do not identify mild cases of OSA as reliably as in-lab assessments.
Given this limitation, home testing for OSA is most appropriate for those patients who have conspicuous symptoms of OSA. This distinction also means that if a home study is negative for OSA, but a high level of suspicion of OSA persists, it is possible that the home study results were inaccurate. In those cases, the study will have to be repeated, or an in-lab study will be required to know with certainty whether OSA is present or not.
Patients diagnosed with OSA are most often treated with continuous positive airway pressure (CPAP) therapy. The CPAP machine increases air pressure in the patient’s upper airway, preventing it from collapsing during sleep. Often CPAP can be started at home, but some patients may need an in-lab study to ensure that the CPAP equipment is effective and properly adjusted to provide maximum benefit. An in-lab study also may be needed if there are concerns about complicating conditions such as congestive heart failure, lung disease (especially chronic obstructive lung disease) and/or risk of hypoventilation.
At Sentara Martha Jefferson Hospital, if a home sleep study is recommended, the patient will be scheduled to come by the sleep lab to pick up the monitor and receive instructions on its proper use. The unit should be returned to the sleep lab the next day so the data can be downloaded and reviewed. A follow-up visit with the sleep clinician is usually scheduled one to two weeks after the patient returns the sleep monitor. During this visit, the clinician will review the test results with the patient and discuss treatment options, as appropriate.
The good news for patients with OSA is that it is highly responsive to treatment with CPAP, and patients can have good outcomes if they follow the recommended treatment plan.
If you think you may need a sleep study, talk to your healthcare provider or call 434-654-5280.
Signs and Symptoms of Obstructive Sleep Apnea
- Loud snoring
- Frequent awakenings
- Episodes of breathing stoppage
- Fatigue/lack of energy
- Daytime sleepiness
- Morning dry mouth and/or headaches