You can sleep in any position you are comfortable with – or not even comfortable, as in long-haul air journeys. Long term, it becomes important to avoid bed sores from pressure, but that isn’t an immediate issue. If you can use a recliner chair, experiment with him to find a comfortable position, make sure he is warm enough, and go with that for now. If you only have a chair and a foot stool, wrap up underneath his legs to cover the gap and keep him warm. I’ve slept like that many nights, with back pain. This counts as an emergency that justifies sleeping tablets, but if you can, limit to 3 nights in a row to avoid getting addicted.
