Obesity hypoventilation syndrome is a secondary complication of morbid obesity where the patient has difficulty breathing fully and deeply. It is believed to be caused by a combination of attempting to deal with the extra weight of fat over the ribcage as well as having fat interfere with the spaces into which the lungs normally expand. It is usually found together with sleep apnea. Patients often stop breathing altogether for a few seconds at a time. This causes extreme fatigue and daytime sleepiness.
The more familiar name of the condition, Pickwickian syndrome, is based on a character from Charles Dickens' The Posthumous Papers of the Pickwick Club (aka "The Pickwick Papers") who exhibited the same symptoms.
Although there are drugs that can increase airway pressure, they are not recommended as they have severe side effects. Although mechanical increases in airway pressure through a ventilator works as a short term solution, the only long term solution is weight loss.