If a passenger has a medical emergency on a flight and a physician or nurse on board responds and provides emergency medical care, what is the liability when the patient decides to sue?

I am wondering about this for international flights and also for flights between Canada and the U.S.

Does it matter what the nationality of the airline is, or the departure and arrival cities?

I have read that some jurisdictions have laws to cover the care provider in this situation, where and when would these laws apply?

If there is a medical emergency in the air I would like to respond. However I am not interested in putting my family and myself at risk of losing our entire savings to a lawsuit-happy patient.