VO2 max refers to the maximum amount of oxygen in mille litres you can use in one minute per kilogram of body weight. The fitter you are, the higher your VO2 max will be thus enabling you to exercise more intensely.
Studies show that you are able to alter your VO2 max by raising your heart rate to between 65-85% of your MHR (maximum heart rate - 220 minus your age) for a minimum of 20 minutes 3-5 times a week.
Although you should be able to raise your VO2 max there are a number of genetic factors which will affect this. Some physical limitations are restrictive on the rate at which energy can be released aerobically.