context: One of the many important jobs of your blood is to deliver oxygen throughout your body. But when you have heart failure, your heart muscle might be weaker and may not pump blood the way it normally would. That means your body doesn't get the oxygen it needs. If that happens, your doctor might suggest that you start oxygen therapy. This therapy lets you breathe in extra oxygen to make sure you get what your body needs. And you can do it in your own home. It's not a cure for heart failure, but it may prevent serious issues caused by low oxygen, such as damage to your heart and brain. It may also help with symptoms like shortness of breath and swelling in your ankles. Your doctor will usually suggest oxygen therapy when heart failure causes very low levels of oxygen. But if your levels are closer to normal, it's more of a gray area. In this case, recent studies seem to show that oxygen therapy may be harmful because you get too much oxygen. More research is needed, so ask your doctor what you should get. The basic idea is that you have a source of oxygen that you breathe in through either a: Mask that goes over your mouth and nose Nasal cannula -- two small tubes that sit just inside your nose The oxygen itself may come as a liquid or a gas in a tank. Or you may get a machine called an oxygen concentrator. Which one is best for you depends on: How much oxygen you need How often you need it -- day, night, or both Costs and what your insurance covers As a gas or liquid, oxygen comes in metal tanks that need to be refilled once they run out. Some tanks are small enough to carry around with you, but they're not usually suggested when you have heart failure. The advantage of liquid oxygen over gas is that the tanks are lighter and hold more oxygen so you don't need as many refills. If you need oxygen often throughout the day and night, an oxygen concentrator may be the better choice, since constant tank refills can be costly and a hassle. This machine pulls oxygen directly from the air so you don't need to worry about tanks or running out of oxygen. It does require electricity, so you'll need a backup plan in case you lose power in your home or something goes wrong with the machine. An oxygen concentrator can weigh over 30 pounds, but it's got wheels, so it can be moved between rooms. Your doctor will measure your oxygen level with either a blood test or a device called a pulse oximeter. The pulse oximeter goes on your finger, toe, or earlobe. It's quick and painless, but not always as accurate as a blood test. Your doctor will then give you a prescription for oxygen therapy, just like you'd get for medicine. It tells you how much oxygen you need and when to take it. Follow these directions closely. Too little oxygen can damage your heart and brain. Too much could slow your breathing and cause other issues. As long as you follow your doctor's directions, oxygen therapy is generally considered safe. You may get minor problems such as: Dry or bloody nose Headaches in the morning Tiredness Oxygen can lead to fires. So you and the people around you need to take steps to stay safe. For example: Avoid open flames, such as candles, lighters, and lit cigarettes or cigars. Don't use lotions and creams that have petroleum in them -- use water-based ones instead. Keep the oxygen at least 6 feet from any heat sources, such as heaters and ovens. No one around you, including you, can smoke while you're taking oxygen. Stay away from substances that easily catch fire -- like paint thinners and aerosol cans -- while using oxygen. It also helps to: Have a fire extinguisher close to you. Make sure your smoke detectors work. Stand oxygen tanks upright -- don't lay them on their sides. Tell your fire department you have oxygen in your home.