@davej I have been in this situation (sort of). A woman on the table behind me in a restaurant started choking on food. Her friends didn't know what to do. I've done some basic first aid courses over the years. I slapped her on the back a couple of times, and was hesitating to grab her and perform the Heimlich. Thankfully, she was able to get some air in and cough up the obstruction without any more help. I felt a fool afterwards, so hopefully I've learned my lesson.