PHRN Corner

Choosing a Home Oxygen System

Many considerations arise when selecting a long-term oxygen therapy (LTOT) system for a patient. The focus of this article is to increase clinicians' knowledge of the clinical and operational differences of LTOT systems so they are able to match those systems to the needs of the patient appropriately. While choices for stationary systems are limited, a multitude of choices exist for portability. Each LTOT patient has his or her own unique needs; therefore, not all of these systems are right for each patient.

Prior insurance approval is generally required for coverage, with most private plans following Medicare guidelines. Medicaid oxygen guidelines vary from state to state. Medicare requires that certain clinical and laboratory criteria be met to qualify a patient for oxygen. In general, laboratory criteria must provide documentation of hypoxemia (ie, PaO₂ ≤55 mm Hg or SaO₂ ≤88% in subjects breathing room air). If the laboratory criteria for hypoxemia are not met, then additional clinical qualifiers (eg, cor pulmonale, congestive heart failure, pulmonary hypertension, or erythrocythemia) are required.

As part of the qualification, the prescribing physician must complete a certificate of medical necessity (CMN). The CMN requires the documentation of an oxygen prescription, but it does not require the physician to specify the type or brand of oxygen equipment. In most cases, the home medical equipment (HME) provider will match the capabilities of the stationary and portable devices to the patients' needs and abilities. Oxygen requirements may change over time. Patients should be re-evaluated periodically while using their home portable system.

Stationary Systems

Liquid Oxygen (LOX) Reservoirs – Oxygen, which is normally a gas, becomes a liquid when stored at a very low temperature. Liquid oxygen is stored in a large insulated liquid reservoir system and it converts to a gas through a controlled evaporation system.

Oxygen Concentrator – Concentrators are electrically powered devices that separate oxygen from the other gases in room air. They deliver oxygen concentrations of ≥90%, which is considered clinically equivalent to 100% oxygen.

Table 1. LTOT Stationary Systems Comparisons

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Portable Systems

A portable system is defined as an oxygen system that weighs less than 10 pounds and can provide a minimum of 4 hours of oxygen therapy.

Compressed Gas Cylinders (CGC) – Small CGC coupled with an oxygen conserver are the most prevalent form of ambulatory oxygen. They are also used as a backup system for individuals who use electrically powered concentrators. Oxygen concentrators with external pressure boosters may be used to transfill (or refill) certain portable oxygen cylinders with pressurized concentrated oxygen.

Common CGC – Capacities and Weights

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Oxygen Conserving Devices (OCD) – Oxygen conserving device systems deliver oxygen to the patient during inhalation only, thus conserving the oxygen that would otherwise be wasted during exhalation. Continuous flow devices deliver oxygen throughout the entire breathing cycle. This consumes oxygen at a more rapid rate, which reduces the amount of time a patient can spend away from his or her stationary unit. Oxygen conserving devices are coupled with portable devices to reduce the weight of portable systems and increase their duration. Many makes and models of OCDs are available, but there are 2 general classifications: Pulse Dose Oxygen Delivery Systems (PDOD) and Demand Oxygen Delivery Systems (DOD).

Table 2. LTOT Portable Systems Comparisons

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Oxygen conserving device settings are depicted by numbers, but they are not equivalent to the settings on continuous systems. Continuous flow systems deliver oxygen in L/min and OCD systems deliver oxygen as a bolus (volume of gas) in mL/breath. To add to the confusion, product performance standardization is lacking. A setting on one OCD is not equivalent to the same setting on another OCD. Oxygen conserving devices have other performance characteristics such as trigger sensitivity and response time, which may affect the response and delivery of oxygen to the patient. Due to these differences and because not all patients can be effectively oxygenated with an OCD, titrating the patient on the specific portable and conserver combination to determine the setting that provides adequate oxygenation is important. Patients should be evaluated during rest, ambulation, and other activities of daily living.

Portable LOX – Liquid oxygen is transferred from the stationary reservoir system to a small portable LOX system. If you compare a similar size portable LOX with a CGC, more LOX than gas can be stored in the portable.

Portable Oxygen Concentrator (POC) – Portable oxygen concentrators are the newest form of portable oxygen technology, and they have gained popularity in the home oxygen market. When considering a POC, one should investigate the unit's battery life, weight, number of pulse dose settings, and oxygen delivery capacity. These can vary greatly among different models.