Use of public funds by a visitor on Holiday due to medical emergency

What are the obligations and implications for the visitor and sponsor, in case the visitor who is on holiday in UK meets with a Medical Emergency and is hospitalized for a long duration. Please throw some light on the same.

NHS hospital treatment:

To find out if you can get free hospital treatment, see information for those visiting or moving to England on the NHS Choices website.

The attachment details the eligible treatment etc.

I know they are not covered by NHS as they are visitor, They had come here with an insurance but the insurance does not cover the whole treatment and it was a medical emergency which was unexpected. So need to understand what are the obligations and implications of the situation as a visitor and a sponsor??

As I understand it, the visitor will be charged at 150% of cost by the NHS. S/he is expected to clear the NHS debt or have a repayment plan in place before any future visits as otherwise the debt, if exceeding £500, can be used as a basis for refusal of future visas. I do not know if the costs can be recovered from the sponsor.

A&E is exempt from charges, but not emergency treatment after being admitted to hospital.

Also see a whole stack of guidance documents in NHS visitor and migrant cost recovery programme.