It’s great you are asking this question before a bedsore starts.

When a person is confined to bed because of a stroke, other illness or an injury, he or she may move very little, if at all. As a result, pressure builds up on specific areas of the body. Skin covering prominent bones is most vulnerable. Examples include:  

• The lower part of your back near the buttocks and your heels if you’re lying on your back
• Your hip and ankle if you are lying on your side

When the person does move, or moves incorrectly, friction may add to the problem of pressure.

In just a couple of hours, that pressure can squeeze shut the tiny blood vessels that deliver blood to the skin and underlying tissue. Without fresh blood to bring in oxygen and nutrients, skin and nearby tissues get weak and eventually break down. The result is a bedsore. Doctors refer to them as pressure ulcers or decubitus ulcers.

The best ways to prevent your father from developing bed sores:

Repositioning.

• Get him out of bed, even if it means just sitting in a chair.
• Encourage him to do what his physical therapist has instructed every day.
• Reposition him when he is in bed. Roll him to his side. Prop pillows under his back to keep him there. Change sides. Ideally, reposition him every 2 hours or as often as you and other family members can.

Nutrition. Insufficient nutrition increases risk of skin breakdown. Make sure he is getting enough calories and protein.

Skin care. Dry skin is a known risk factor for bedsores. Probably because it creates friction. Rub in a moisturizer on his back a couple times per day. This is also another chance to move him.

Support surfaces. Support surfaces include mattresses and added padding that goes over them. There are multiple options. None have been proven to be better than another. Also there are special beds with “dynamic” surfaces. They automatically change the pressure under the patient. They are usually very expensive. I would not recommend spending the money just to prevent bedsores.