3 Types of Low-Flow Oxygen Delivery Systems

Low-flow oxygen is a standard treatment option for anyone of these cardiopulmonary diseases:

However, once your doctor prescribes low-flow oxygen, finding a reliable oxygen delivery system can be challenging. There are many different options on the market, and they all have various features—so how do you know which is best?

There are several things to consider before purchasing a low-flow oxygen delivery system. However, before we examine the pros and cons of the 3 main oxygen delivery systems for home use, let us briefly define what a low-flow oxygen delivery system is.

Low-Flow Vs. High-Flow Oxygen Delivery Systems

Oxygen delivery systems are categorized as either:

  • Low-flow
  • High-flow

For the most part, low-flow oxygen includes devices that deliver a small amount of oxygen into your airways that does not result in pressure build-up in your lungs. The amount of oxygen is so tiny that aside from the nasal cannula sitting in your nostrils, you will not notice the oxygen coming through the cannula for the most part.

On the other hand, there are oxygen delivery systems that deliver high-flow rates anywhere from 8–40 liters per minute through a nasal cannula. At these high-flow rates, there is usually a small amount of pressure that builds up in your lungs, which helps you breathe easier during acute episodes of shortness of breath. Due to the highly-dynamic nature of these devices, they are usually used in hospitals under 24-hour supervision by a respiratory therapist.

Also, high-flow oxygen therapy includes positive pressure ventilation via a mechanical ventilator or a noninvasive positive airway pressure device like a CPAP or BIPAP machine. These devices are generally used in hospitals, but in more severe cases, they can be prescribed and used at home under the regular supervision of a pulmonologist (a doctor who specializes in the respiratory system).

For this article, we will be focusing on low-flow oxygen delivery systems.

Which Low-Flow Oxygen Delivery System is Best?

While no system is necessarily better than another, your circumstances will dictate which is best for you. Here are some questions to consider before purchasing an oxygen delivery system:

  • Is the device capable of delivering the exact amount of oxygen prescribed by your doctor?
  • Do you leave your home often?
  • When you leave your home, do you stay out for a long time?
  • Do you exercise regularly?
  • When you are out of your home, are you engaging in strenuous activities?
  • Does your home have any mobility challenges (such as two stories or limited walk space)?
  • Do you have enough strength to carry or pull a portable oxygen device?
  • Do you breathe mostly through your nose or your mouth?

The answers to these questions will help guide your decision on which oxygen delivery system is best for you.

3 Types of Low-Flow Oxygen Delivery Systems

There are 3 types of low-flow oxygen delivery systems to consider: compressed oxygen cylinders, liquid oxygen, and oxygen concentrators.

Types of Low-Flow Oxygen Delivery Systems

1. Compressed Oxygen Cylinders

Oxygen cylinders, or oxygen tanks are the most common delivery system and are widely used. Since they function pneumatically by slowly releasing pressurized oxygen to achieve a steady flow, they do not need electrical power to work.

As mentioned above, one of the main benefits of owning a compressed oxygen cylinder is that it does not need a power supply to work. Since it does not have any electrical parts, there is no need for a battery or electrical power.

Compressed oxygen cylinders can also be equipped with a pulse-dose flow meter to manage the flow rate of the cylinder. Without a pulse-dose flow meter, an E-cylinder (the most common cylinder type for portable use) only lasts about 5 hours at 2 liters per minute. However, with a pulse-dose flow meter, you could extend the life of an E-cylinder, at the same flow rate, for up to 17 hours.

Another benefit of oxygen cylinders is that they come in 2 different sizes: a D-cylinder and an E-cylinder. The D-cylinder is small enough to carry over your shoulder in a pouch, while the E-cylinder is small enough to carry in a wheeled carrier.

Without a pulse-dose flow meter, compressed air tanks only last between 2–5 hours depending on the size and the liter flow. So if you need portable oxygen for an extended period, you will have to plan and take multiple tanks with you, which can be cumbersome.

Another disadvantage is that compressed air tanks are heavier than most other oxygen delivery devices, especially the E-cylinder. If this is the tank you are given, you will also need a wheeled carrier to transport your tank to avoid having to pick it up and potentially injuring yourself.

Also, you will always have to carry a key to open the cylinder if it is not already open with a flow meter attached to it. If you already have the tank open with the liter flow turned off, then you will not need the key. However, if you need to use a new tank, you will have to use the key to open the new cylinder.

Educate yourself with our Free Oxygen Therapy Guide

2. Liquid Oxygen Systems

Liquid oxygen systems are unique because they use a liquefied form of oxygen that turns into a gas when released. To use this system, you must also have a sizeable liquid oxygen reservoir in your home to refill your portable device before extended use.

With liquid oxygen, you can refill your portable tank from your large reservoir at home whenever you need to. With this backup reservoir, you will not need to make frequent calls to your supplier for refills.

While it might seem like a benefit to having a large reservoir in your home for easy refills, the refill procedure is relatively complicated. There is a definite learning curve to using liquid oxygen, and there are some severe hazards such as cold burns or fires if mishandled.

Also, since liquid oxygen evaporates quickly, you will always have to refill your tank just before you leave your home to avoid losing too much oxygen from evaporation.

3. Oxygen Concentrators

Oxygen concentrators are a unique oxygen delivery system. They function like air filters that remove everything except oxygen from the air. Once this filtration occurs, you can reach almost 100% pure oxygen with the device. And since this filtration occurs inside the unit itself, there is no need to refill tanks.

As mentioned above, oxygen concentrators do not need to be refilled. These devices run on electrical power and can be used on-the-go with a battery pack, resulting in up to 10 hours of continuous use for some models. And once the battery runs out, all you have to do is plug the device into an electrical outlet to recharge.

Over the long term, concentrators are more cost-effective. As long as your device is well-maintained, they are known to last up to 1,500 hours of straight use. Also, most portable oxygen concentrators have a continuous and pulse-dose setting built into the device, so you can quickly move from continuous to pulse-dose flow with a touch of a button.

The only significant disadvantage of an oxygen concentrator is that it needs electrical power to function, and while electrical power is far easier to access and deal with than scheduling a tech to refill your tanks, it is wise to prepare for unscheduled power outages by setting up a backup power generator in your home.

Comparison of Oxygen Delivery Systems

Compressed Oxygen Cylinders
Compressed Oxygen Cylinders Delivery Systems
Liquid Oxygen Systems
Liquid Oxygen Oxygen Delivery Systems
Oxygen Concentrators
Portable Concentrators Oxygen Delivery Systems

None Required
Standard Home outlet for Reservoir
Rechargeable Battery

Refill Process:
Home Delivery Available
Transfer from Home Reservoir
None Required

Air Delivery:
100% Oxygen
100% Oxygen
95% Oxygen, 5% Ambient

Bulky and Heavy
Handbag to Backpack Size
Handbag to Rolling Suitcase Size

Flow Rate Adjustment:
Analog via Valve Gauge
DAnalog via Valve Gauge
Digital Setting

Oxygen Capacity:
Dependent on Tank Size
0.7 - 1.0 Liters for Portable Tank

FAA Approved:
Most meet FAA requirements

Important Things to Consider

Your insurance provider plays a role in determining which oxygen delivery system you ultimately qualify for. However, that decision is also determined by your specific oxygen needs and what your daily activities are.

If you plan to purchase a device out of pocket, then your insurance coverage will not be a factor. However, if you plan to ask your insurance to cover your device, it is vital that you clearly explain your symptoms and daily activities to your doctor. The last thing you want to happen is to be prescribed a stationary oxygen concentrator if you are still very active and regularly leave the house for extended periods of time. In this case, a portable oxygen concentrator with a long battery life will give you more freedom to continue your active lifestyle.

Final Thoughts

These 3 oxygen delivery systems all dispense oxygen sufficiently for medical treatment but with varying levels of maintenance and portability. Before accepting the first option that is given to you, consider the pros and cons of each device. Then, be sure to request a device that will accommodate your lifestyle.

Page last updated: October 10, 2018


About Scott Ridl: Scott joined American Medical Sales and Rentals in 2008 as a Web Manager and Content Writer. He is a writer and designer. He is extensively trained on oxygen therapy products from leading manufacturers such as Inogen, Respironics, Chart, Invacare, ResMed and more. Scott works closely with respiratory therapists and oxygen specialists to educate the community about oxygen therapy products, COPD, asthma and lung diseases. He writes weekly columns and is passionate about educating the community on oxygen therapy and respiratory issues.

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