How do you handle a guest who collapses at the reception on arrival?

Your people sir should have a training in first aid so incase of emergencies in the reception they can help guest.  They should be knowlegeble in this field. Instead waiting for other departments or ambulance for50 years to rescue, it might be too late.

i try to be comfort with him and bring for him water and drink 

found fast way for hes problem 

If they can talk ask them if they need any help if its nothing serious? if they are not in a condition to explain what is wrong with them Try and put them in the recovery position, do not panic, call the ambulance and ask for assistance what to do while they arrive on the scene.