All you need to know about Oxygen Cylinders

During the second wave of the COVID-19 pandemic, one of the major issues was the oxygen deficiency and lung infections faced by COVID patients. Due to this, more and more patients underwent oxygen therapy – which is the use of medical devices like oxygen cylinders and concentrators to help make breathing easier.

So, let us take a look at oxygen cylinders, what they are used for, how they work, and the risks and dangers associated with them as well.

What is an oxygen cylinder?

Oxygen cylinders (or oxygen tanks) are medical devices meant to provide supplemental oxygen to patients. It helps people who are facing respiratory issues or those who have low blood oxygen levels.

An oxygen cylinder, or tank, stores oxygen, which is then dispensed to the patient using an oxygen mask, nasal tubes, or an oxygen rebreather.

Types of oxygen cylinders

The oxygen in the tank is either kept in gaseous form in a pressured gas cylinder, or in liquid form in a cryogenic storage tank. Both store 99.5% pure oxygen.

Compressed oxygen gas – in such cylinders, oxygen is extracted from the air, and it is compressed and filled inside aluminium tanks up to 2,200 pounds per square inch (PSI) of pressure. When the gas is released, this high pressure forces the oxygen out and into the oxygen delivery device (like the oxygen mask or nasal tubes).
Liquid oxygen – in these tanks, oxygen is cooled to -182.8°C until it is in liquid form. This is then stored in a special tank that keeps the liquid cool. When this liquid oxygen is exposed to warmer temperatures, it converts back into a gas that immediately flows outwards through the oxygen delivery device.

While liquid oxygen is less bulky to store, it requires special equipment and training to use; hence it is not commonly used as compressed oxygen gas.

How does an oxygen cylinder work?

An oxygen cylinder is essentially a vessel that stores oxygen. When it is used in medical facilities or at home, they help to deliver supplemental oxygen to patients who cannot get the needed amount of oxygen on their own (these levels can be checked using a pulse oximeter).

At the top of the cylinder, a flow regulator converts the pressurized oxygen in the tank into a specific flow that can be measured, known as litres per minute (LPM). There are two main types of flow regulators: continuous flow and pulse-dose flow.

Continuous flow – such regulators allow one to set a specific LPM and dispense the same level of oxygen until either it is shut off or the tank runs out. It is usually used for patients who require oxygen on an intermittent basis.
Pulse-dose flow – these regulators allow one to increase the effectiveness of their oxygen cylinder. It does this by releasing short bursts of oxygen when the patient inhales. This way there is oxygen wasted when they exhale. The machine must still be set to the prescribed LPM as in the continuous flow regulator.

Oxygen cylinders also come in various sizes based on the volume of gas contained within (and thus how long a person can use the oxygen in the tank before it runs out). The most common ones include:

Type of Tank	Height (in inches)	Capacity (in litres at 2,200 PSI)
ML-6 (Transported with carrier bag)	7.6	165 litres
B (or M-6) (Transported with carrier bag)	11.5	164 litres
C (or M-9) (Transported with carrier bag)	11	255 litres
D (or M-15) (Transported with carrier bag)	16.5	425 litres
E (or M-24) (Transported with a cart or wheelchair bag)	25.5	680 litres
M-60 (Not portable)	23	1738 litres

When should you use an oxygen cylinder?

An oxygen cylinder is to be used only when recommended by a registered medical professional. This is usually done when a person requires supplemental oxygen due to having low blood oxygen levels.

Blood oxygen levels can be monitored using a device like a pulse oximeter. It measures SpO2 or oxygen saturation. Normal levels of SPO2 are above 95-92% in a healthy individual. If it falls below this, supplemental oxygen might be recommended.

If the use of an oxygen cylinder is recommended, the doctor will also decide if it needs to be in the hospital or if it can be done at home. They will also determine how frequently or for how long oxygen therapy is needed.

What is the difference between an oxygen cylinder and an oxygen concentrator?

Like an oxygen cylinder, oxygen concentrators are also used to provide supplemental oxygen to patients. But they are different in a number of ways:

	Oxygen Cylinders	Oxygen Concentrator
How it works	Stores a fixed amount of pressurized oxygen, which is gradually used until the tank empties	Filters oxygen from the surrounding air
How the oxygen is delivered	Using a nasal tube or a mask	Using a nasal tube or a mask
Refill or replacement	Need to be replaced or refilled once the tank is empty	Do not need to be replaced or refilled
Portability	Portable versions are available	They are portable

Since oxygen cylinders need to be refilled, smaller portable models (such as the M-6 or M-9) may be used in conjunction with an oxygen concentrator. The concentrator can then be used to refill the cylinder using a "home-fill" system.

How are oxygen cylinders helpful in fighting COVID-19?

Those who are suffering from COVID-19 often develop a number of respiratory and lung problems. According to the WHO, about 14% of patients show severe symptoms that require hospitalization and oxygen support.

Thus, oxygen cylinders have become an important tool in the fight against COVID-19, especially when used with a pulse oximeter to monitor levels of oxygen in the blood. Oxygen cylinders help to provide supplemental oxygen to those who require it.

Unfortunately, they serve as a temporary measure in short-term acute situations like COVID-19. They are used to help ease the burden of breathing for patients so that they have the time to heal. It is also important to remember that oxygen therapy cannot instantly restore a patient's oxygen levels to normal.

What are the steps for using an oxygen cylinder?

An oxygen cylinder is to be used only when recommended by a doctor. While some types of cylinders can be used at home, they are more commonly used in hospitals and other medical facilities. If they are being used at home, there are some steps to be followed:

Step 1: Before handling the cylinder, ensure your hands are clean, and that the cylinder is also clean and free from any damage, and from oil or grease.
Step 2: Attach the regulator to the valve at the top of the tank.
Step 3: Turn on the tank using the valve on the top (you can use the provided cylinder wrench to do so).
Step 4: Check the contents gauge to ensure that there is sufficient gas content in the cylinder.
Step 5: Adjust the flow of oxygen to the prescribed LPM using the control on the regulator, and check that oxygen is flowing.
Step 6: Attach the nasal tubes or oxygen mask to the oxygen outlet.
Step 7: Ensure your mask or tubes are in working order and put them on.

If using a mask: Place the mask over your mouth and nose, securing the band behind your head or around your ears and making sure there are no gaps around the edges.

If using nasal tubes: Position the nasal tubes upward into your nostrils and loop the tubes over your ears. You can use the tube adjuster to tighten the tubes under your chin.

Step 8: When not in use, turn off the oxygen tank and ensure that you store the cylinder in a horizontal position in its carrier and firmly secured so that it does not roll around.

Are there any risks in using an oxygen cylinder?

Never use an oxygen cylinder without guidance from a medical professional, as getting too much (or too little) oxygen may do more harm than good. Some of the risks include:

Too much oxygen can lead to oxygen toxicity.
Too little oxygen can lead to hypoxia. This can cause damage to the heart, brain, and other organs.
Not cleaning the tubing regularly can lead to a build-up of bacteria and fungi, and thus to serious infections.
Oxygen is highly combustible. Thus, oxygen cylinders should never be used around open flames, heaters, or people smoking.
Aerosols (like hairspray or perfume), oil-based face creams, or petroleum products (like Vaseline) should not be used while using oxygen cylinders.

What to keep in mind before getting an oxygen cylinder?

Since there are a number of oxygen cylinders of various types and sizes available in the market, there are some things you need to keep in mind before getting the device:

Check with a doctor whether an oxygen cylinder or an oxygen concentrator is better for your needs.
Ask your doctor how many litres per minute of oxygen is required for you, as oxygen cylinders can supply up to 10 LPM.
Choose the size of the cylinder (ex. M-6, M-9, M-15, etc.) based on how much oxygen you require (i.e., the prescribed LPM) and on how portable you need the device to be.
If you cannot regularly get your oxygen tank refilled, see if you can also acquire an oxygen concentrator to create a home-fill system.
Based on your oxygen needs, choose a nasal tube or an oxygen mask. While masks can be used for higher oxygen needs, the tubing will allow for more freedom of movement.