Q. An obese 50-year-woman presents to her PCP for fatigue and shortness of breath upon exertion. She states the SOB has worsened during the past nine months. About one year ago she was diagnosed with obstructive sleep apnea due to being overweight, but due to lack of insurance coverage was unable to purchase a CPAP machine. She has never smoked, denies any marijuana use, and does not let anyone smoke in her home. She is five feet, eight inches tall and weighs 295 pounds. There are no abnormalities on cardiorespiratory examination. Chest x-ray is unremarkable. Morning arterial blood gas shows: PaO2: 65 mm Hg PaCO2: 57 mm Hg pH: 7.35 Serum HCO3–: 30 mEq/L Which of the following is most likely the patient’s condition?