Liquid Oxygen Therapy

Date: January 28, 2016

Updated February 4, 2026

What Is Medical Liquid Oxygen?

Medical liquid oxygen is a form of oxygen used in long-term oxygen therapy. The oxygen is cooled to very low temperatures until it becomes a liquid and is stored in insulated containers. When the liquid warms, it turns back into a gas that can be delivered through standard oxygen tubing and cannulas.

Because liquid oxygen is denser than gaseous oxygen, a small volume of liquid can provide a large supply of oxygen gas. One liter of liquid oxygen can produce about 860 liters of oxygen in gas form. This allows a portable liquid oxygen unit to hold many hours of oxygen in a container that is relatively small and light. Liquid oxygen systems are designed to provide continuous flow oxygen, and some setups may also support pulse flow, depending on the equipment and the prescription.

Liquid oxygen is stored under lower pressure than compressed gas cylinders. The insulated containers help keep the oxygen cold and reduce evaporation. Liquid systems have been used for many years in hospitals and are also used in some home oxygen programs, when ordered by a healthcare professional.

What Is Liquid Oxygen Therapy?

Liquid oxygen therapy is a form of supplemental oxygen treatment in which a patient receives oxygen from liquid oxygen containers instead of compressed gas cylinders or oxygen concentrators. It is prescribed for people whose lungs and heart cannot maintain adequate oxygen levels on their own.

Clinicians may consider liquid oxygen for some patients who need higher continuous flow rates, longer run times away from home, or a system that does not rely on household electricity. The choice between liquid oxygen, concentrators, or cylinders depends on the patient’s diagnosis, activity level, home setting, and medical guidance. Any decision about oxygen therapy must be made by a licensed healthcare professional.

A typical liquid oxygen (LOX) system has two main components. Both are insulated, Thermos-like containers that help keep the oxygen cold so it remains in liquid form until it is used.

The Two Major Components of Liquid Oxygen Therapy

  1. Storage reservoir
  2. Portable, refillable container

Liquid Oxygen Reservoir

The liquid oxygen reservoir is a larger stationary container that stays in the home. An oxygen supplier fills the reservoir on a regular schedule, often every one to three weeks, depending on the size of the tank and the prescribed flow rate. The reservoir does not use electricity and has few moving parts, which helps limit maintenance needs.

When filled, a typical liquid oxygen reservoir may weigh about 90 to 170 pounds and hold roughly 21 to 41 liters of liquid oxygen. When converted to gas, this range equals approximately 16,750 to 37,916 liters of oxygen. At a flow of 2 liters per minute, 37,916 liters of gas could last around 316 hours, or about 13 days of continuous flow, not including normal evaporation losses.

Reservoir Evaporation

Liquid oxygen will slowly warm and vent small amounts of gas even when the system is not in active use. This natural evaporation shortens the total time that the stored oxygen can last. For example, some HELiOS reservoirs lose about 1.2 pounds of oxygen per day through evaporation. Oxygen-conserving devices and pulsed delivery can reduce the amount of oxygen used during breathing, but evaporation from the reservoir still occurs.

HELiOS Liquid Oxygen Reservoir

Links to Liquid Oxygen Reservoir

Portable Liquid Oxygen Unit

The second part of a liquid oxygen system is the portable unit. This smaller container is filled from the home reservoir and can be carried in a shoulder bag, backpack, or built-in strap system. Patients typically use the reservoir as the primary source of oxygen when at home and switch to the portable unit when leaving the house.

The portable unit does not require electricity and receives oxygen directly from the liquid stored inside. Many portable units offer continuous flow settings, and some also offer pulse flow settings, depending on the model and prescription. The oxygen supplier refills the home reservoir, and the patient or caregiver refills the portable unit from the reservoir according to manufacturer instructions.

Because liquid systems are not dependent on household power, they may be considered in areas where electrical outages are common. Backup plans for all oxygen systems, including liquid oxygen, should always be developed with a healthcare professional and oxygen supplier.

Liquid Oxygen Maintenance Requirements

Liquid oxygen systems require routine care but little technical maintenance. The stationary reservoir should sit on a stable, level surface and may be secured to a wall if recommended. Any condensation bottles used to collect excess moisture need to be emptied and cleaned regularly. The outside of the tank can be wiped with a damp cloth to remove dust.

Only trained personnel should fill or exchange the main reservoir. Patients and caregivers should follow the manufacturer’s instructions when refilling portable units and when handling any freezing around connectors. Any concerns about performance, leaks, or ice buildup should be reported to the supplier.

Prescribing Portable LOX (Liquid Oxygen)

Portable liquid oxygen may be prescribed for patients who need long-term oxygen therapy and spend time outside the home. Its compact size, low weight, and ability to provide continuous flow can be helpful in certain situations, such as extended outings or higher-flow prescriptions. Pulse flow settings may also be available, depending on the unit.

Professional societies and clinical studies have examined liquid oxygen and other long-term oxygen systems in chronic lung disease. However, the decision to use liquid oxygen instead of concentrators or cylinders must be individualized. Only a licensed healthcare professional can determine the most appropriate oxygen delivery system for a specific patient.

Comparing Portable Liquid Oxygen to Portable Oxygen Concentrators

Portable liquid oxygen systems commonly support continuous flow and, in some cases, pulse flow. In contrast, many portable oxygen concentrators use pulse flow, and a smaller number are designed to provide both continuous and pulse flow oxygen when used as directed.

Examples of portable oxygen concentrators that have continuous flow capability include the following devices, which are intended for use under medical supervision:

  1. Oxlife Independence
  2. Eclipse 5
  3. SimplyGo
  4. DeVilbiss iGo2

The charts below on the original page compare typical sizes, weights, run times, and sound levels between selected portable oxygen concentrators and liquid oxygen products such as the HELiOS and Companion series. These comparisons are averages and do not replace product labeling or professional guidance.

Comparing Liquid Oxygen to Portable Oxygen Concentrators

Portable liquid oxygen units are often smaller and lighter than many portable concentrators that provide continuous flow. Liquid systems can provide long run times between refills because of the high density of liquid oxygen. When a portable unit is empty, it can usually be refilled from the home reservoir in a short period, often in a few minutes, following manufacturer instructions.

Liquid oxygen units themselves do not generate motor noise while delivering oxygen, because they do not compress room air. In contrast, portable concentrators draw in air and use internal compressors and filters, which produce sound during operation. The exact sound level varies by model.

Comparing LOX to Pulse Flow Portable Oxygen Concentrators

Pulse flow portable oxygen concentrators are generally designed to be compact and light, with small enclosures and low carry weights. In many cases, these concentrators are smaller and lighter than portable liquid oxygen units. However, liquid systems can provide higher continuous flow settings and longer run times in some situations. The best option depends on the prescribed oxygen flow, mobility needs, and clinical recommendations.

Liquid Oxygen Review

Like other oxygen systems, liquid oxygen has strengths and limitations. Understanding these trade-offs helps patients and caregivers discuss options with healthcare professionals and oxygen suppliers.

Advantages of LOX

  1. High oxygen concentration delivered from liquid storage
  2. Ability to support higher continuous flow rates with some systems
  3. Long oxygen supply duration between refills
  4. No motor noise during oxygen delivery
  5. Does not rely on household electricity for normal operation
  6. Large oxygen capacity in a relatively compact home reservoir
  7. Portable units that can be refilled from the home reservoir
  8. Short refill times for portable liquid units compared with battery charging
  9. Potential for more neutral appearance than some larger equipment

Disadvantages of LOX

  1. Limited availability of liquid oxygen suppliers in some areas
  2. Steady evaporation loss from the reservoir, even when not in active use
  3. Need for regular deliveries or refills from a medical oxygen provider
  4. Short, louder noise periods during the filling of portable units
  5. Risk of freezing at the connection between the reservoir and portable unit if filling is not done correctly

Summary of Liquid Oxygen Therapy

Liquid oxygen therapy is one option for long-term oxygen treatment. It offers high oxygen concentration, supports higher continuous flow in some systems, and can provide long run times without relying on household power. These features may be helpful for certain patients who need continuous flow oxygen at higher settings or who spend long periods away from home.

The main limitation of liquid oxygen therapy is access to a reliable service provider for home reservoir refills. In some rural or remote areas, liquid oxygen delivery may not be available, and other systems may be more practical. For patients in regions where liquid oxygen providers are active, LOX can be one of several options that a healthcare professional may consider when planning long-term oxygen therapy.

Resources

  1. Liquid Oxygen Use Time Duration Chart for several liquid oxygen devices manufactured in the United States.
  2. HELiOS and Companion LOX Specifications provided by Chart Industries.
  3. Cancaster B, Ranking the Top Portable Oxygen Concentrators with Pulse Flow includes concentrator review and comparison.
  4. Cancaster B, Ranking the Best Portable Oxygen Concentrators with Continuous Flow includes concentrator comparison chart.
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