Sleep Apnea
By Donald R. Elton, MD, FCCP
Lexington Pulmonary and Critical Care

Sleep apnea is by far the most common sleep disorder encountered in clinical practice. Patients are profoundly affected by this disorder that frequently goes undiagnosed for years. Non invasive therapy (usually nasal CPAP - Continuous Positive Airway Pressure during sleep) is effective in 90% of patients. Treated sleep apnea patients are among the most pleased patients you will encounter as treatment often results in a fast and dramatic improvement in quality of life and general health.


Why it happens
Most sleep apnea is obstructive and is caused when the normal relaxation of sleep causes a loss of upper airway muscle tone. This normally results in snoring which is a vibration of the tongue and soft palate that occurs when a person breathes against a partially obstructed airway. In patients with obstructive sleep apnea, the combination of upper airway collapse and loss of muscle tone in the chest and abdomen result in either a cessation or significant decrease in airflow. Hypoxia (lack of oxygen) from the resulting apnea (stopped breathing) or hypopnea (shallow breathing) leads to an arousal (usually too brief to be recalled by the patient) which allows for a return of muscle tone and thus breathing. After a breath or two, the hypoxia is reversed and the patient goes back to sleep. This cycle repeats throughout the night.


Consequences
The pathology of obstructive sleep apnea results from frequent awakenings (as many as 50 to 100 awakenings per hour) and from repeated episodes of hypoxia. The frequent awakenings cause sleep to be non-restorative and cause excessive daytime sleepiness (EDS). The episodic hypoxia results in headaches, increased risk of strokes and heart attacks, and when severe, in systemic and pulmonary hypertension and eventually right sided heart failure in the worst cases.


Recognition
The two key symptoms that should lead you to suspect sleep apnea are the combination of snoring and excessive daytime sleepiness. With this combination in an adult there is as much as an 80% chance that a sleep study will document a clinically important degree of obstructive sleep apnea. Daytime sleepiness can be scored using the standardized Epworth Sleepiness Scale. This allows the patient or significant other to rate the patient's likelihood of dozing in 8 specific circumstances with scores assigned from 0 (no chance) to 3 (high chance). The situations are: Sitting and reading, watching TV, sitting inactive in a public place, a passenger in a car for an hour, sitting and talking with someone, sitting quietly after lunch, and in a car stopped for a few minutes in traffic. Scores of 5 or under are considered normal. Scores over 10 are definitely abnormal. Note that a patient's spouse will usually rate the patient higher and perhaps more accurately than the patient.

Anatomical clues that sleep apnea may exist include obesity (though lack of obesity does not exclude sleep apnea), excessive soft tissue over the external neck, an elongated soft palate (one in which you can't easily see the tip of the uvula without a tongue blade), large tonsils, and a mandible that doesn't extend as far forward as the maxilla. Sleep apnea patients frequently are diagnosed as having depression, chronic fatigue syndrome, difficult to control hypertension, recurrent refractory headaches, unexplained edema (cor pulmonale), unexplained pulmonary hypertension, abnormal Holter monitoring (arrhythmias, tachycardia, bradycardia, heart block during sleep) and other disorders.


Testing
Patients are typically initially evaluated by the sleep consultant to gather historical information and to assess airway anatomy and potential medication related problems that can lead to sleep disorders or affect the effectiveness of various treatment options. Seeing the patient before the study results in a more meaningful study interpretation and makes it easier to recommend the right treatment for the patient. The initial office visit is also used to explain the pathophysiology and treatment options for sleep disorders to the patient and to make sure the patient understands the sequence of events in working up and treating his or her disorders if they are diagnosed.

Testing is normally done in a sleep laboratory under the supervision of a sleep technologist who can immediately correct technical problems such as misplaced leads etc and can make observations and interventions while the study is going on. Some studies can be performed in the home if there is clinically little doubt as to the diagnosis though the risk of having to repeat the study due to technical problems is higher in an unattended study. Home studies typically do not measure as many parameters as can be measured in the sleep laboratory but home studies are usually less expensive than lab based attended studies.

A preliminary report is made available to the sleep consultant within a day or two of the study with the full data report sent to the sleep consultant within a week. An interpretation report is then dictated and sent to the referring or personal physician. If intervention is needed, it may be initiated over the telephone before the patient returns for formal follow-up. This allows the follow-up visit to be used to evaluate the response to treatment in many cases.

If a patient has obvious significant sleep apnea, the sleep laboratory will interrupt the study and start a CPAP (continuous positive airway pressure) titration study where the patient is placed on the CPAP and allowed to go back to sleep while the technologist adjusts the pressure level while monitoring the patient's sleep to find the minimum pressure level needed to correct the sleep apnea and resultant hypoxia. If there isn't enough time to find the optimum level during the first night of study, a second night will be used for this purpose. If the patient is found to have significant abnormalities they may be started on CPAP at home empirically pending the formal CPAP titration study.


Treatment
In 90% of patients, nasal CPAP is the only treatment needed and results in dramatic improvement even after the first night of use. The worse the patient's initial disease, the more likely the clinical results will be dramatic as a minimally symptomatic patient might not see much subjective difference with treatment. Some patients require more time and work to get them used to using CPAP. There are a variety of masks and CPAP device programming issues that can get the difficult patient used to CPAP and once the patient gets a full night of sleep and sees the clinical effects they are highly motivated to continue. Some patients have obstruction so severe that CPAP isn't adequate treatment or loss off CPAP could be life threatening. In these cases, if their upper airway anatomy has a correctable defect, surgery to correct the defect may be appropriate and the sleep consultant would then refer the patient to an ENT for this purpose. After surgery the CPAP titration study would be repeated as CPAP requirements would likely be different. Unfortunately, surgery as primary therapy in unselected patients for sleep apnea is only about 50-60% effective and may only correct the snoring thus masking the actual severity of disease. By limiting surgery to those patients who fail CPAP and have an anatomical problem to correct, the effectiveness of surgery is much better.

Follow up
Once the patient is effectively treated, routine follow-up by the sleep physician is not normally required. Patients are advised they may need a repeat CPAP titration study if they gain or lose more than 25 lbs of weight or if they find they are again having symptoms of sleep apnea (perhaps medication related etc.)