Brain stroke with hiccups and low spo2.

My father in law is diagnosed with brain stroke due to high sugar and the brain stem has affected. This has caused his inability to stand due to balance issues and very little speech disability. His sugar, BP is all controlled and the latest CT scan hasn't reported any further damage and is recovery. But since recently he now needs oxygen support as his saturation goes low. As low as 78 at times. When he got stroke he also got this continuous hiccups which are not cured yet and comes and goes in batches. At times the UREA goes up and at times the Ceratin goes high. Need to consult for these things 1. Hiccups - why are they and are they because of the stroke and it's medication? And why isn't it stopping 2. The Oxygen saturation going low is new. What is the reason? Is the brain stroke medication making the lungs relaxed which is causing this? 3. What are the next set of diagnosis need to be taken with respect to chest and lungs for hiccups and oxygen low?