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Hypersomnolent, Hypercapnic, and Morbidly Obese

Reviewed By Sleep and Respiratory Neurobiology Assembly

Submitted by

Stephen W. Littleton, MD

Fellow in Sleep Medicine

University of Chicago

Chicago, IL

James A. Rowley, MD

Associate Professor of Medicine

Wayne State University School of Medicine

Detroit, MI

Babak Mokhlesi, MD, M.Sc.

Assistant Professor of Medicine & Director, Sleep Disorders Center and Sleep Medicine Fellowship Program

University of Chicago Pritzker School of Medicine

Chicago, IL

Submit your comments to the author(s).


A 54 year old morbidly obese man was referred to the Sleep Disorders Clinic because of hypersomnolence and suspicion of obstructive sleep apnea. He complained of habitual loud and disruptive snoring, frequent nocturnal choking episodes and witnessed apneas for the past 8 years. He started developing excessive daytime sleepiness in the last 5 years. He had gained approximately 45 kg in the last 10 years. The Epworth Sleepiness Score was 16/24. He also complained of mild dyspnea on exertion. He retires to bed at approximately 11 pm with a short sleep latency. He wakes up at 7:30 am. He experiences an average of three awakenings per night but is able to fall asleep in less than 10 minutes.

Past medical history is significant for hypertension and type 2 diabetes. His medications include metformin 1000 mg twice daily, hydrochlorothiazide 25 mg daily, and lisinopril 40 mg daily. He denies drinking alcohol and he is a nonsmoker. There is no significant family history.

Physical Exam

The patient was in no distress and the vital signs were normal. Height was 170 cm; weight 132 kg pounds with a BMI of 45.4 kg/m2. Oral examination demonstrated Mallampati class 4 airway and no overbite or overjet. The neck circumference was 51 cm. Lungs were clear to auscultation. The heart was regular in rate and rhythm without any murmurs or gallops. There was 1+ symmetric lower extremity edema. Room air pulse oximetry was 91% while sitting and resting. Laboratory data from a routine basic metabolic panel obtained few weeks prior to clinic visit revealed a serum bicarbonate level of 34 mEq/L (normal 24-28 mEq/L).

Question 1

Which of the following features has been shown to be predictive of obesity hypoventilation syndrome (OHS)?


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