In order to understand overlap syndrome, you need to be clear on two conditions: COPD and OSA.
What is COPD?
Chronic obstructive pulmonary disease (COPD) is a condition that results from slow movement of air in the airways of the lungs due to a combination of loss of elasticity and narrowing of the inner airways of the lungs, resulting from chronic inflammation.
What is Obstructive Sleep Apnea?
Obstructive Sleep Apnea (OSA) is a condition that results in cessation of flow of air due to a blockage in the throat and the inability to overcome that blockage during sleep.
What is the presentation when the two overlap?
A person with COPD will have difficulty moving air through his lungs during wakeful hours when he is aware of his symptoms.
During sleep, healthy individuals will have a natural pattern of breathing where the number of breaths and the size of each breath will decrease. That results in a lowering in the level of oxygen and rise in carbon dioxide in the blood. Obviously, a person with COPD, who is already having difficulty moving air while awake, will have even more serious consequences, when the breathing is naturally decreased during sleep. This is called overlap syndrome and refers to two conditions that present and co-mingle with each other. The term is also used in other conditions like connective tissue disorders.
Who is at risk for this condition?
COPD presentation can differ among patients. Some will have more severe disease than others. Some individuals have predominant emphysema features which is the over inflation of the lungs and loss of elasticity. Others have chronic bronchitis features with thickening of the airways and excess mucus production.
If someone has airway thickening he will feel the burden of the resistance to flow of air in the throat more pronounced at night, and the resulting lowering of oxygen and rise in carbon dioxide.
Normally there are compensatory mechanisms originating in the brain that signal the lungs to increase the breathing pace and depth to compensate for these (resistance to air flow) changes. These mechanisms are called “respiratory drive centers.” During sleep the level of activity in these centers are also decreased, allowing for some tolerable changes in oxygen levels.
There are people with COPD who have low or borderline low levels of oxygen during the daytime. They are very likely to spend most of the night with abnormally low levels of oxygen, resulting in health consequences and yet, most of the time they will not feel frank symptoms.
How is overlap syndrome diagnosed?
The key is to diagnose both COPD and OSA in the same individual.
The first step in this process is to correctly diagnose COPD. Not everyone who is short of breath and/or smokes has COPD. When someone experiences shortness of breath that “is out of the ordinary,” or feels like he “can’t keep up with someone his size or age in activities of daily life,” they often have COPD. Sometimes a chest x-ray is suggestive of COPD, because the radiologist identifies hyperinflation of the lungs. This would indicate a primary diagnosis of emphysema. A pulmonary function test (PFT) would then be performed to confirm the diagnosis. This test will also measure the severity of the disease.
The levels of oxygen can then be determined by a blood test which checks for the level of oxygen in the artery (arterial blood gas), or by an** oximeter**, which senses the color of the patient’s finger and estimates the saturation of oxygen. The oximeter test is less invasive and less painful. An oximeter test is often performed along with a pulmonary function test.
Obstructive Sleep Apnea is often suspected because a spouse or bed partner witnesses episodes of cessation of breathing in the patient, or the patient awakens from what seems to be “choking spells.” Those so-called choking spells are actually the person re-initiating breathing, after a spell of total cessation of breathing. Coupled with an additional complaint of early morning headaches should prompt the person to seek an evaluation by his doctor, and confirmation of OSA through sleep studies should be done.
Some screening tests for OSA come in form of questionnaires. The Berlin Questionnaire estimates the probability of sleep apnea. The Epworth Sleepiness Score measures the sensation of daytime sleepiness. These two questionnaires can help to determine the probability of an OSA diagnosis.
The gold standard confirmatory test is an overnight sleep study in a lab with monitoring.** How is overlap syndrome treated?**
It’s necessary to treat the two individual conditions. Medications have the potential to reverse COPD abnormalities up to a point. Some individuals with COPD do have more reversible symptoms than others. Some individuals need oxygen on a round-the-clock 24-hour basis. It is important to know that the use of oxygen is not to relieve shortness of breath. Its purpose is to saturate the blood with acceptable levels of oxygen.
There are currently no drugs to treat obstructive sleep apnea. If someone with OSA presents with the obstruction in the upper airways, this can only be overcome with the use of a positive airway pressure machines (CPAP). A sleep study will help to identify the ideal pressure settings.
Some prevention tips to keep in mind:
- It’s important to seek a diagnosis of COPD and OSA if you suspect that you have either or both of these conditions.
- It’s important to realize that you can have both conditions.
- Learn the risk factors for COPD and OSA.
- Stop smoking to reduce the risk of developing COPD.
- Lose weight if you are overweight to lower your risk of OSA.
- Make sure that if you are having trouble getting used to CPAP, you discuss your difficulties with your doctor. There are different mask sizes and also certain oral appliances that realign the mandible, which can help with breathing in mild cases of OSA and replace the need for CPAP.
The danger of untreated overlap syndrome
There are many possible negative health outcomes if overlap syndrome is not treated. Cardiac conditions like congestive heart failure (CHF), atrial fibrillation (AF) can be exacerbated. High blood pressure will be more difficult to control if overlap syndrome is not adequately treated. The person’s brain function will also likely deteriorate if overlap syndrome is not addressed and treated.
Flenley DC. Sleep in chronic obstructive lung disease. Clin Chest Med 1985; 6:651–661.
Ioachimescu OC, Teodorescu M. Integrating the overlap of obstructive lung disease and obstructive sleep apnoea: OLDOSA syndrome. Respirology 2013; 18:421