Classic sleep apnea in the patient. Cessation of breathing causes nocturnal hypoxia and systemic hypertension/arrhythmic/sudden death can persist. PaO2 is normal during day and decreased during episodes and at night. Classically seen in Obese patients such as the patient in the question stem.
Lung volume will decrease in obesity hypoventilation syndrome. Even though this patient is obese, he has all the clinical features of sleep apnea
How does OSA lead to peripheral edema and loud S2?