Where to sell oxygen machine in Chongqing?

My family's situation and you check not much, I was in the Daping Hospital to the elderly to see the disease, discharged from the hospital when the doctor said must be at home oxygen, would like to buy an oxygen concentrator, I was in the Daping Hospital next to the Pharmacy and Pharmacology Bureau downstairs Rehabilitation Home medical equipment store to buy, I bought the Invicta Oxygen Concentrator can be turned on continuously for 24 hours, they are guaranteed for 3 years, door-to-door, I looked up on the Internet, it is true that, on the Internet, there is a Cheaper, did not dare to buy, in case of bad, how to do, they told me that the Invicta oxygen concentrator is the best oxygen concentrator, the return rate is very low, very low, almost no, since it is for the elderly to use, buy a good point, use also assured, you can also go to them to see.