You should have your doctor or home care company provide an appropriate backup solution. You should confirm the selection of any inverter with the manufacturer of your CPAP equipment. Before attempting to implement a battery system for your CPAP, you should verify the electrical information with a person competent in electrical device power supplies, and confirm with the manufacturer of your specific CPAP device that your device will not be harmed or the warranty voided by the proposed setup. You should have a qualified person help install your system and instruct you in the safe and proper use of it. Follow carefully the instructions and cautions of the manufacturers of the CPAP, battery, battery charger, and inverter in addition to normal cautions when using electrical current.
Batteries contain sulfuric acid which can cause serious burns and blindness.
In case of splashing on to a person with battery acid, wash off with copious amounts of clean water and get medical attention. Neutralize spills with baking soda. Before measuring the specific gravity, disconnect the battery from the charger and inverter, open the cell cover and and use a large piece of paper or cardboard to fan away any gas. Avoid splashing or spilling the fluid. Wear eye protection.