The Epworth Sleepiness Scale (ESS) is used to provide a patient self-report of likelihood to fall asleep in a set of hypothetical situations, and has only a modest ability to predict OSA. Although an ESS score of 12 or greater is can be considered abnormal, patients with ESS scores lower than 12 with known risk factors for OSA should still raise clinical suspicion. However, the sensitivity of the ESS to detect clinically important OSA is insufficient to be used as a screening tool in the absence of other clinical data.
Maintenance of wakefulness test (MWT), in which the time it takes the patient to fall asleep or stay awake (respectively) is recorded via electroencephalographic readings over the course of a day.
The Berlin questionnaire addresses the presence and frequency of snoring, waketime sleepiness or fatigue, and history of obesity or hypertension, and has a sensitivity of 86% to detect sleep apnea (RDI>5) among patients who have persistent and frequent symptoms in any 2 of these domains.
The STOP-BANG questionnaire assesses the 8 most common factors associated with OSA: Snoring, Tiredness during daytime, Observed apneas, high blood Pressure, Body mass index (>35), Age (>50 years), Neck circumference (>40 cm), and Gender (male); research has shown that a BMI cutoff of 30 instead of 35 can be used in certain ethnic groups. STOP-BANG can be used preoperatively to assess patients who might be at higher-than-normal risk for surgical complications. A score of 5 to 8 has a high probability that a surgery candidate has moderate to severe OSA.
The NAMES assessment is a novel approach that combines neck circumference, airway classification, comorbidities, ESS score, and snoring, along with physical exam findings and patient history, to identify patients with moderate to severe OSA.
The goals of the PSG are (1) to quantify how much time is spent in the various sleep stages, and (2) to document any abnormalities or changes that occur during these stages.
Polysomnography results are reported using the AHI (Apnea-hypopnea index). An AHI score of less than 5 is normal. A patient can be diagnosed with OSA syndrome with an AHI of 5 to 14 along with daytime symptoms or an AHI of 15 or greater independent of other symptoms. Apnea-hypopnea index scores can also be used to assign severity: an AHI of 5 to 15 indicates mild OSA; 15 to 30 indicates moderate OSA, and scores greater than 30 indicate severe OSA.
The mainstay of therapy for OSA involves positive airway pressure (PAP). The most common form of PAP is continuous PAP (CPAP); other forms include variable or bilevel PAP (BiPAP or BPAP) and automatically-adjusting PAP (APAP).
CPAP uses continuous pressurized airflow to keep the patient's airway open during sleep using a compressor that has a snug-fitting mask covering the nose (or nose and mouth) to stabilize the upper airway and prevent collapse.
Typically, the initial amount of pressure is identified through the titration portion of the diagnostic PSG, while taking into consideration the patient's comfort. Titration should be to the lowest pressure required to decrease apneic and hypopneic episodes.
BiPAP may be used for patients who cannot tolerate CPAP or for patients with neuromuscular diseases who require assistance with nighttime ventilation. It employs 2 levels of pressure: a higher inspiratory PAP and lower expiratory PAP for easier exhaling. Automatically-adjusting PAP devices automatically titrate as necessary. Some of the newer models of CPAP also humidify the air, which diminishes dry mouth and may afford more comfort over the original models.
The optimal duration of CPAP use per night appears to be variable. A study involving nearly 150 patients with severe OSA reported that nightly CPAP use of longer durations -- but only up to a maximum of 7 hours -- leads to a greater percentage of patients achieving normal function.[52] Currently, patients are generally considered adherent if they use CPAP for at least 4 hours per night on at least 70% of all nights.
Patient complaints typically focus on dry mouth or throat, nasal irritation, discomfort with the pressure, and air leaks or problems with the masks.
CSA (Central sleep apnea) is characterized by episodes of disrupted breathing throughout the night; other symptoms include daytime sleepiness, restless sleep, and chronic fatigue, and may include morning headaches. Patients may report swallowing difficulties or changes in their voice; they may also report other symptoms based upon the causative pathophysiology of the disorder. Medical conditions that might lead to CSA include stroke or encephalitis affecting the brain stem, heart failure, some neurodegenerative disorders (Parkinson disease and multiple sclerosis), obesity, and the use of certain medications -- particularly narcotics. Patients with CSA may benefit from oxygen, nasal CPAP, or, in some cases, BiPAP. Treating the underlying comorbidity is imperative. Patients should avoid sedative medications, but may be prescribed medications to stimulate breathing. Adaptive servoventilation has been shown to be an effective treatment for CSA patients without heart failure.
Patients who live at higher altitudes and have moderate to severe OSA are significantly more difficult to treat with PAP. In addition, central apnea becomes significantly more common at increasing altitude in both diagnostic and treatment portions of PSG in patients with significant OSA. An alternative treatment approach for these patients is low-flow oxygen followed by titration with CPAP/BiPAP in patients who develop central “complex” apnea on PAP treatment. This approach can lead to overall good or optimal titration in 95% of titrated patients. One danger associated with central apnea that develops in OSA patients is an intolerance to PAP therapy. This can result in a higher level of untreated OSA among these patients, which can, in turn, have negative effects on multiple disease processes, potentially leading to higher morbidity and mortality.
