The Science Journal of the American Association for Respiratory Care


August 2002 / Volume 47 / Number 8 / Page 879

New Technologies for Lighter Portable Oxygen Systems

Dr Tiep's report in this issue of RESPIRATORY CARE which describes a new oxygen-conserving device, helps to draw attention to new trends in portable oxygen therapy.1 As patients have moved from hospital to home, oxygen therapy has provided a cost-effective alternative for payers and an improved quality of life for patients. The Nocturnal Oxygen Therapy Trial2 demonstrated the value of continuous oxygen therapy, and industry has provided systems to administer oxygen in the home. The Third Oxygen Consensus Conference concluded that most long-term oxygen therapy (LTOT) patients are ambulatory, and so portable oxygen should be available for patient mobility.3

See The Original Study on Page 887

Fig 1

Initially, portable oxygen was available in small cylinders (Figure 1), but the operating times were not sufficient to meet patients' needs for longer times away from the stationary system. Larger (E-size) cylinders provided the volume for longer operating times but were too heavy to carry and not ambulatory, according to the Third Oxygen Consensus Conference.3

In 1965 the first liquid oxygen (LOX) system was introduced for home use. Union Carbide, working with Dr Tom Petty, developed a small portable system that had the weight and range to meet the patient's need for ambulation and that could be refilled from a base unit (Figure 2).4 This started a major shift in home oxygen therapy, towards LOX as the first choice for mobile patients. In 1986 Medicare changed the way oxygen was paid for, moving from a fee-for-service program to a flat-rate, prospective payment method. Since LOX has a higher cost, associated with the service necessary to refill the base unit, home medical equipment providers moved to oxygen concentrators and small cylinders to control expenses.

The standard had been set, and patients and clinicians expected provision of a portable oxygen system with weight and range similar to a LOX portable. Oxygen-conserving devices (OCDs) thus became a viable alternative (Figure 3). OCDs had been available since 1984, but with a fee-for-service payment system there was no incentive for their use. Now an OCD can make a small cylinder last 3 times longer than was possible with continuous-flow oxygen and can compete with LOX portables.

Fig 2

Initially OCDs were not well received.5 Many patients and clinicians said they tried the OCD, and it did not work. Some problems were related to technical issues of the sort that occur with any new product on the market. Recent research provides another possible cause for poor results.6 Each manufacturer determines what volume of gas to provide at each setting and reports that to be equivalent to continuous flow. Bench testing found that one device set on 4 was delivering 66 mL/breath, and another device set on 4 was delivering 34 mL/breath. That volume difference created confusion and the perception that the units did not work. With the focus on oxygen savings ratio rather than patient oxygenation, OCDs had an acceptance problem. Now it is recommended that the patient be tested with the prescribed OCD unit, at the expected activity levels.7

There is a lesson to be learned from this experience. Clinicians need to be informed of the performance capabilities of each piece of prescribed equipment. The respiratory products industry is growing rapidly, and, without direction from clinicians, the manufacturers determine how a product should operate. In home care, marketing materials claim, for instance, that one oxygen device lasts longer than another or that the oxygen savings ratio is better than a competitor's. Those are important points if the patient is to be adequately oxygenated. If patient oxygenation is not the primary goal, you can conserve oxygen by reducing the flow from 2 L/min to 1 L/min and not have to purchase an OCD.

Fig 3

The LTOT market is growing rapidly, and patients are being placed on oxygen systems earlier in the course of disease.8 The baby boom generation is moving into the years when many of them will become LTOT candidates. This younger patient group will be better informed of options for demand oxygen systems that meet their individual needs.

Recently-introduced products include lightweight, portable LOX systems that weigh less than 4 pounds and have an operating range of 6-8 hours at a typical setting of 2 (Figure 4). Concentrators that can fill cylinders in the home have been available for several years and are becoming good financial alternatives for providers of highly ambulatory patients (Figure 5). One manufacturer has received Food and Drug Administration clearance for a product that can liquefy oxygen from a concentrator and fill a LOX portable. Such home systems that can refill portable oxygen devices will give unrestricted freedom to patients who have in the past budgeted their oxygen supply based on the number of portable systems delivered by the provider.

Fig. 4

Single-source systems that provide for both stationary and ambulatory needs will bring LTOT to a new level. A portable concentrator that has recently received Food and Drug Administration clearance for sale to the market weighs 9 pounds and can operate on battery for up to 50 minutes at a setting of 2 (Figure 6). This is the first step towards a single-source system, but this unit would not meet the recommendations of the Third Oxygen Consensus Conference for ambulatory oxygen.3 New alternatives such as ceramic or electrochemical generation of oxygen may allow the development of oxygen systems that are light enough to carry and provide for the oxygen needs of highly ambulatory patients both at home and away.

Oxygen patients are becoming more involved in their therapy and are using the Internet to learn about their diseases and the therapy products available.9 Quality of life is important to a patient, and knowing the options for care helps them to discuss their needs with the physician. Consumer-driven LTOT care is new to the industry and creates opportunities and challenges for clinicians. An informed patient will force the clinician to stay current on products and procedures.

Fig 5

The respiratory therapist needs to understand the operation of any piece of home-use respiratory equipment and to use that knowledge and his or her clinical skills to maximize the patient's benefit from that equipment. Each manufacturer will attempt to provide educational material on the operation, benefits, and value of its product, but the manufacturer's motive is to sell equipment. We have seen that claims of superior oxygen savings ratio or operating time were valuable for marketing but complicated the application of OCDs. With the rapid development of new LTOT products, the clinician needs to be involved and informed of the clinical efficacy of the products and their potential value to the patients.

Robert W McCoy RRT
Valley Inspired Products
Burnsville, Minnesota

Fig 6


  1. Tiep BL, Barnett J, Schiffman G, Sanchez O, Carter R. Maintaining oxygenation via demand oxygen delivery during rest and exercise. Respir Care 2001;47(8):887-892.
  2. Continuous or nocturnal oxygen therapy in hypoxemic chronic obstructive lung disease: a clinical trial. Nocturnal Oxygen Therapy Trial Group. Ann Intern Med 1980;93(3):391-398.
  3. Conference Report. New problems in supply, reimbursement, and certification of medical necessity for LTOT (Summary of the third consensus conference held in Washington, DC, Mar 15-16, 1990). Am Rev Respir Dis 1990;142:721-724.
  4. Petty TL. Historical highlights of long-term oxygen therapy. Respir Care 2000;45(1):29-36; discussion 36-38.
  5. Block AJ. Intermittent flow oxygen devices; technically feasible, but rarely used (editorial). Chest 1984;86(5):657-658.
  6. Bliss PL, McCoy RW, Adams AB. A bench study comparison of demand oxygen delivery systems and continuous flow oxygen. Respir Care 1999;44(8):925-931.
  7. Petty TL, Casaburi R. Recommendations of the Fifth Oxygen Consensus Conference. Respir Care 2000;45(8):957-961.
  8. Frost and Sullivan. United States Oxygen Therapy Devices Market. 2001. Available at (accessed June 6, 2002).
  9. Emphysema Foundation For Our Right To Survive (EFFORTS). (accessed June 6, 2002).

Correspondence: Robert W McCoy RRT, Valley Inspired Products LLC, 14301 Ewing Ave S, Burnsville MN 55306. Email:

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