Oxygen Therapy

Oxygen (O2) is the primary fuel for the body. Every organ needs O2 to work. Just like gas for a car, if your body’s O2 level is too low, your organs won’t work. You won’t be able to think clearly, your heart may not be able to pump as well, your kidneys will not be able to filter and clean your blood effectively, etc. But unlike gas for a car, O2 is not just necessary for your body to perform. If a car runs out of gas it stops running. But it does not start to fall apart. It just sits there unable to move. If your body O2 level gets too low your organs start to actually shut down and even begin to be injured by lack of oxygen. Eventually, your organs can be permanently damaged or even die if O2 is low enough, long enough.

Patients with advanced chronic lung disease often have low blood O2 levels. If it is severely low, they get distressed and need immediate aggressive medical attention. But if it is mildly, or even moderately low, patients can often function, though usually not optimally. Most times patients with mild to moderately low oxygen feel bad. But occasionally they don’t, or at least they are not aware that they could be feeling much better if their oxygen was good.

We know from scientific studies that advanced lung disease patients with low O2, defined as a blood oxygen saturation of below 90%, benefit greatly by using supplemental O2 gas. In fact, these patients live significantly longer if they use O2 for at least 15 hours per day. As you might expect, hypoxemic patients (patients with low blood oxygen) feel better, are able to do more, and in general have better health, with oxygen use. So that is why physicians prescribe O2 for patients with advanced lung disease and low O2.

Oxygen is non-addictive. That is, using O2 does not make your lungs weak, or dependent upon the O2.

O2 use is really quite safe in general, but there are some basic precautions to take with medical O2 in the home. First, it is very important to know that O2 is flammable. So fire and ignition materials should be kept out of the immediate vicinity (at least 5 feet) of an O2 gas source. Naked wires or other fire hazards, as well, should be kept away from oxygen. Second, O2 delivery systems should be kept in well ventilated areas. By doing so, there is very little risk of raising the oxygen content of a room or building significantly, or enough to increase the chance of a general fire.

Oxygen for patients is usually ordered by physicians for patients meeting criteria, and delivered to the patient by a medical oxygen supply company. Nearly universally, patients inhale the O2 gas from a “nasal cannula”. Small tubing that delivers O2 into the nostrils. The gas travels up through the nose and then down into the back of the throat where it is inhaled without any conscious effort by the patient. Just normal breathing brings the extra oxygen into the lungs. The tubing is hooked up to one of several types of O2 gas supply sources. The O2 can come from a tank of concentrated oxygen, an oxygen concentrator, or from liquid oxygen.


  • Concentrated O2 gas – this is the oldest system of O2 for the home. Compressed O2 gas comes in various sized metal canisters. Large canisters are for use in the home and small canisters can be taken portable. The gas is let out into the oxygen tubing through a valve, with a “flow regulator” that determines how much comes out of the tank in liters per minute. New tanks get delivered to the home when the old tanks run low on O2.
  • Liquid oxygen – these systems run on liquid oxygen. A storage tank is refilled periodically with cold oxygen – which is in liquid form. When warmed up the liquid O2 turns into a gas that can come out of tubing. There are now portable systems that use liquid O2. They are the lightest of the portable O2 systems.
  • Oxygen Concentrator – this system runs on electricity. It pulls oxygen from the air and concentrates it to be let out into the oxygen tubing that goes to the patients. Traditionally this has been a workhorse of home O2. Recently light weight, battery operated systems have come out for portable use. These systems do not need to be serviced with O2 gas or liquid oxygen.


The O2 gas flow to nasal cannula can come from the oxygen source as continual flow, or intermittent flow. The usual way to deliver O2 is a continual flow from the source. For example, a common continual flow rate of gas through the nasal cannula is 2 liters of O2 gas per minute. This is happening through all parts of the respiratory cycle, even when patients are not breathing in. This may seem wasteful to have O2 flowing when not breathing in. Indeed, some of the O2 gas goes into the surrounding air. But also, some of the O2 gas, between breathes, goes into the nose and upper airway, and forms a “reservoir of oxygen”. When the patient does take a breath, a higher concentration of O2 is inhaled from this reservoir, in addition to the O2 from active flow. Intermittent O2 gas flow is designed to conserve O2 gas, especially for the portable systems, that have a limited O2 supply, or a limited battery life. There are several types of intermittent flow systems, but they all deliver O2 flow timed to inspiration. Theoretically the intermittent flow O2 systems can do as good a job at supplying O2 as the continuous systems. The reality is, though, that many patients just don’t do as well with the intermittent system.

The flow rate o f oxygen is usually adjusted to increase or decrease the amount of oxygen that patients are receiving. Standard oxygen sources can deliver from ½ liter per minute of O2 to 5 liters/minute (L/min). Every liter/minute of oxygen increases the percentage of O2 the patient breathes by 3 – 4 %. Room air is 21% O2. So if a patient is on 4 L/min O2 flow, then he or she is breathing air that is about 33 – 37% O2. The normal practice is to adjust O2 flow for patients to be comfortably above an oxygen blood saturation of 90% at rest. It is often, however, the case that patients need more oxygen for exercise. So for example a patient may use 2 L/min O2 at rest, but need 4 L/min with exertion.

Occasionally, for patients needing high flow rates we consider two other devices to increases the amount of oxygen a patient can get. One is an “oximizer”. These devices are, essentially, mini O2 reservoirs, that hang off the nasal cannula, and allow the patient a larger source of potential oxygen when taking a deep breath. A “transtracheal oxygen cannula” is a cannula, placed directly into the trachea that delivers O2 gas. The cannula is placed through a small tunnel created by an ENT surgeon, through the front of the neck, directly into the main breathing tube called the trachea. These devices have been frought with complications and our practice, does not use them any longer.

Lastly, many patients don’t like to be seen wearing oxygen. They find it embarrassing, and fear it to be socially isolating. Well, that’s where attitude makes all the difference. Think of oxygen as just another tool in your tool belt to do what you need to do. Some of us need medicines to do what we need to do, some need a knee brace. We all need cars, busses, or trains to get around. Well oxygen is just gas for the car, in some lung diseases. Don’t let O2 limit you, let it take you where you want to go.

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