Why is the best way to wake someone from a deep sleep?

Why is the best way to wake someone from a deep sleep?

Chris Idzikowski (Director of the Edinburgh Sleep Centre) gives expert video advice on: What happens to my brain when I sleep?; What happens to my muscles when i sleep?; What happens to my breathing when I sleep? and more...

The best way to awaken somebody is really just to call out their name, do that sort of quietly and repeatedly.