Obstructive Sleep Apnea (OSA) is an extremely common public health problem present in 2% to 4% of the general population. It has been linked to the development of hypertension and is a risk factor for the incidental development of stroke, coronary artery disease, congestive heart failure, and atrial fibrillation (a common irregular heart rhythm).
Obesity & Sleep Apnea
About 70% of people with OSA are obese. Conversely, the prevalence of the disorder among obese people is approximately 40%. In morbidly obese patients (BMI≥45 kg/m2 ), the prevalence of OSA ranges from 50% to 77% and in those with BMI of 60 or more, the disorder occurs in 90%. For every 20lb increment in weight, the risk for OSA increases by more than two-fold while an increase in the body mass index by one standard deviation is associated with a four-fold increase in the prevalence of OSA. It is accepted that central obesity exacerbates OSA because of fat deposits in the upper airway.
Research confirms that OSA is more common in men than women. Obesity can lead to critical narrowing of the upper airway. Excess body weight affects the mechanics of the airway. Fat deposits have a negative impact on the neural control of respiratory muscles. Genetic factors may affect fat distribution.
The increased fat deposits in the upper airway (pharyngeal and the submental regions) cause soft tissue enlargement and contribute to a critical narrowing of the airways. Airway swelling (mucosal edema secondary to vibration trauma related to snoring, vascular congestion, and the inflammatory status related with obesity per se) contribute to anatomical narrowing.
Diagnosing Sleep Apnea
Screening and treating OSA should be an integral part of the preoperative and postoperative care of the bariatric surgical patient because of the high prevalence of OSA in bariatric patients and the consequences of undiagnosed and untreated OSA in the postoperative period (respiratory complications).
Polysomnography at an accredited sleep center is appropriate to identify treatable comorbid sleep disorders for obese patients presenting with sleep disturbances. Weight loss in those who are obese reduces the severity of OSA regardless of the method used, although surgical procedures may produce more objective results.
The two main reasons to detect and treat OSA are to improve symptoms and to decrease cardiovascular risks. Data shows that treatment of OSA improves symptoms and quality of life.
There are two common ways to diagnose obstructive sleep apnea, in lab testing known as a Polysomnography or PSG (gold standard) and Home Testing known as HSAT.
OSA severity is rated by the sleep study AHI, the hourly rate of apneas (cessations in breathing) and hypopneas (upper airway blockages or obstructions) averaged over the total sleep time, or, in the case of HSAT, by the REI. An AHI of 4 per hour or less is considered normal. Mild OSA is diagnosed with an AHI of 5 to 14 per hour, moderate OSA with AHI of 15 to 29 per hour, and severe OSA with AHI being 30 per hour or higher. In most laboratories, correlation of the AHI with specific sleep stages and body positions is usually performed to determine whether positional therapy may be offered, as many patients have OSA only during the supine sleep position (position-dependent OSA), and some manifest OSA only during REM sleep in the supine position.
Mild OSA is diagnosed with an AHI of 5 to 14 per hour, moderate OSA with AHI of 15 to 29 per hour, and severe OSA with AHI being 30 per hour or higher. In most laboratories, correlation of the AHI with specific sleep stages and body positions is usually performed to determine whether positional therapy may be offered, as many patients have OSA only during the supine sleep position (position-dependent OSA), and some manifest OSA only during REM sleep in the supine position.
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