Low-cost airline seats are usually cramped and uncomfortable, even for those who are fit and well. They can make it very difficult to administer care to medical passengers.
Sometimes it is better to have the extra room provided by a scheduled airline economy seat. However these only provide marginally more space and hence comfort.
One extra economy seat can provide much greater comfort in most situations. It is often more economical than a single business class seat.
To ensure extra seats are available they must be purchased in advance.
Two extra seats can allow for a leg to be elevated throughout a flight. This is often recommended by treating doctors and requires permission from the airline.
Some airlines will provide leg elevation by folding forward a seat in the row in front.