What Causes Extreme Sleepiness After A Meal With The History Of Narrowed Carotid Arteries?

My husband has obstructive sleep apnea and uses a CPAP. He also has narrowed carotid arteries. As soon as he eats his first meal of the day, he s overcome by extreme, almost debilitating sleepiness which lasts for several hours. Is this because of the blood shunt to his gut after eating which leaves even less blodd flowing to his brain through the narrowed arteries?