Not saying it's the same, but after several neck dissections, even my latest mandibularlectomy surgery, I do feel swelling in my throat. At some point of times, I was sleeping on a recliner, felt like sleep apnea gasping for air when suddenly awaken. Once I went to the ER after all my teeth extractions, and was admitted, given anti-inflammatories. Also, I do sleep on an incline bed, which helps, but still can feel and see the swelling in the morning, and was sleeping on my side, usually non surgery dude down, seemed to collect less fluid, which usually goes down somewhat from the accumulated fluids buildup finding other pathways to go. Even last night. I tried resting on my side, but it felt like my throat was swelling, so I went back on my back on an incline.

The a/c also seemed to help. Without such, it seems I don't get enough air and feeling of throat tightness. Not sure if the cold helps with inflammation or I just got used to it.

I suggest mentioning such to his doctors and asking about exercise and physical therapy, which can help with the lymphatic flow since it was disrupted by surgery and takes a while to find alternate routes. Over time, fluid build-up, internal and expert so, can cause fibrosis, which happened to me and had a leather neck, which created problems with later surgeries. In some cases, there wasn't enough drainage after surgery with the drainage tubes/bulb, and Drs have to drain dome fluids by needle. His doctors are the best source since they know the patient and performed his surgery.

Good luck. Hope this helps