Agreed. But if the doctor clears you for exercise, you might wanna try boxing. It jump starts your cardio because it's immediately strenuous, and it also toughens your leg muscles. Might help with the double bass drumming.
While boxing is great excercise,as with any excercise,after you're medically cleared,and given age factors,you need to start GRADUALLY,then work your way up to full out cardio.You don't start out running 6 minute miles,when first starting to run,and you don't summet Everest when first learing mountian climbing........... right?
The same as you don't pick a Dream Theatre tune with Portnoy thundering away on double bass,for a first song to learn,when first picking up the sticks.
See a doctor first,who'll give you a complete exam ,and with breating problems,a lung function test(totally painless) to determine pulmonary fitness..
There is no short cut or magic pill to cardio/pulmonary fitness.You have to do the work.While the O2 may give a temporary,short term solution,it is .....temporary.So, you need to put the controllers down,put away the video games,and do some excercise.....pronto.There are some programs like Billy Banks Tai-Bo workouts that build muscle and cardio/pumonary fitness.Remember,you're also not in your twenties anymore.
But...see a doctor first....and do it now.If you smoke....stop.And put down the cheese burgers,soda and tocos.You'll be doing yourself,and your future self ......a big favor.
Steve B