Breathing Easier Through the Years

Vol. 17 •Issue 2 • Page 43
Breathing Easier Through the Years

Reimbursement and patient convenience drive oxygen therapy’s evolution.

More Than 225 years ago, English clergyman and chemist Joseph Priestley discovered oxygen by heating red mercuric oxide and capturing a colorless gas discharge. When he inhaled the gas he labeled “dephlogisticated air,” he noticed a “light and easy feeling.”

“Who can tell but that in time this pure air may become a fashionable article in luxury?” he remarked. That comment is not far from true, as people today use oxygen for both medical and recreational purposes.

However, it only was in 1922 that innovative storage and delivery techniques enabled oxygen’s use in medical therapy. Alvin Barach, MD, was the first clinician to systematically employ oxygen tents to treat bacterial pneumonia. Oxygen delivery has evolved dramatically since then, becoming a medical necessity for a growing number of patients. Already, approximately one million patients with chronic obstructive pulmonary disease receive supplemental oxygen treatment.

Making oxygen

Engineers and clinicians have developed several other methods of separating oxygen from the atmosphere since Priestly’s initial experiment. The two most common, liquefaction and filtration, form the foundation of today’s long-term oxygen therapy.

Cooling gas compounds to a liquid state allows for the separation of the gases. In this state, they have the most efficient storage capability, which is why most gases used in volume today are stored and transported in this manner. Liquefied oxygen’s expansion ratio of 860 to 1 has opened new possibilities for the home oxygen patients’ benefit. Filtration, or pressure swing adsorption, is a method gaining popularity because it allows for small amounts of oxygen to be generated as needed.

Early hospital oxygen systems

Originally, hospitals used high-pressure compressed gas cylinders to store oxygen. Large cylinders were moved to the patient’s bedside for therapy, while smaller cylinders were used to transport the patient within the hospital for special procedures or emergencies. When hospitals began using a piping system to deliver oxygen to each patient’s room, they retained the large cylinders as a backup system in case the piping failed. When patients moved home for LTOT, they continued using large cylinders until more sophisticated systems became available.

Improving portable oxygen delivery

In 1965, Thomas Petty, MD, Master FCCP, introduced a new era of portable oxygen for LTOT patients who previously had relied on compressed gas cylinders. He worked with chemical and polymer company Union Carbide to develop a small liquid oxygen portable device that was paid for by the local Medicare provider.

The weight-to-operating time ratio and greater storage capacity of liquid oxygen (LOX) allowed for a lighter system that lasted approximately twice as long as compressed gas systems. This has afforded patients greater freedom to leave their homes and engage in exercise and recreation.

Hospitals that had replaced their piping system with liquid oxygen also began using small LOX units for basic patient transport because the lightweight, long-lasting portables could be filled on site.

Before long, cylinder manufacturers tackled the reimbursement and competitive challenges presented by the more agile LOX systems. They developed aluminum cylinders, regulators, and carts to compete with the weight efficiency and price of LOX systems. Their new cylinder sizes and options changed as patients pressed for lighter, easier-to-carry systems that allowed for greater mobility during daily activities.

The arrival of concentrators

However, neither device could maintain a hold on the home delivery market. In the late 1970s, home oxygen concentrators began offering a more convenient method of providing stationary oxygen.

Concentrators did not need regularly scheduled refills, which reduced the provider’s expense of visiting homes. And while compressed oxygen cylinders still needed to be refilled, they remained less expensive than LOX systems, which needed to be refilled about every 10 days.

The race was on to see which system would win the battle for LTOT in the home. Patients and physicians often favored LOX portables because of their long operating time and light weight, yet concentrators were effective for stationary oxygen.

A turning point

Oxygen conserving devices revolutionized the home LTOT competition by changing the oxygen delivery method from flow-base to volume-base delivery. In the flow-base method, oxygen dose is dependent on inspiratory time to provide a prescribed amount of oxygen that varies with respiratory rate. Volume delivery with a conserving device can give the entire effective oxygen dose early in the inspiratory cycle then turn off — which allows the delivery of a specific oxygen dose to the patient’s airway.

One of the first commercial conserving devices was the reservoir cannula. This device increased the oxygen storage around the patient’s airway, allowing a lower oxygen flow to accomplish the same oxygenation goal as a higher setting. The next available piece of equipment, a pulse dose system, was the first electronic conserving device. This unit’s technology made oxygen last three times longer than it would have on the same continuous flow setting.

These oxygen-conserving devices allowed compressed gas cylinders to compete with LOX portables by efficiently dosing oxygen and eliminating the wasted oxygen flowing when a patient was not inhaling.

Equivalency claims bring confusion

Comparing these devices was complicated. Manufacturers seeking physician, payer, and Food and Drug Administration approval claimed dose equivalency between the systems. However, the settings on conserving devices were similar but not the same as continuous flow system settings. This circumstance created a great deal of prescription dosage confusion. While one conserver set on its “2” setting could dispense 16 mL of oxygen, another conserver could release 32 mL of oxygen on the same setting.

No dose volume standards existed for oxygen therapy, so manufacturers determined what they felt was equivalent. Most often they used a lower-dose volume in order to claim a higher saving ratio. This created confusion and the perception that conserving devices did not work.

Two classes of conservers emerged based on market demands for better equivalency. The less expensive pneumatic conserver did not require batteries. It often used a dual-lumen cannula, with one lumen to sense inhalation and exhalation and the other channel to deliver flow. Electronic conservers controlled doses better, yet were more expensive and required a power source. While each method has been proven effective, dosing variability and other practical issues need to be understood to ensure proper patient oxygenation.

Hybrid oxygen systems

The increase in the number of LTOT patients and the subsequent economic pressure has stimulated the development of new home oxygen systems. The goal of therapy is to keep the patient out of the hospital by maintaining effective blood oxygen levels during all activities. This requires oxygen systems flexible enough to meet patients’ needs, yet efficient enough to provide cost-effective care. Pressure from payers, providers, and patients have driven new product development for home oxygen therapy.

Portable oxygen remains one of LTOT’s greatest challenges. The more active oxygen therapy patients want light and long-lasting systems. Yet while refilling a portable system is the greatest cost to the home care provider, it persists as the payers’ lowest reimbursement. New hybrid options have been manufactured to address this complex issue.

Home concentrators that fill portables

Concentrators that fill compressed gas cylinders in the home entered the market a few years ago. Models differ among manufacturers, but the principles remain the same. A concentrator generates oxygen then transfers the oxygen as compressed gas in the portable cylinder. Oxygen monitoring equipment ensures the gas’s purity. This allows patients to refill cylinders themselves, and it saves the home care provider from visiting patients’ homes to exchange cylinders.

Concentrators that fill LOX portables now are available. Again, the concentrator generates oxygen for the portable, but rather than pressurizing the gas, the gas is liquefied and trans-filled to the portable. This gives patients the advantage of both a lightweight and long-term use portable.

Portable concentrators

After numerous clinician requests, manufacturers finally have introduced portable oxygen concentrators. These machines give patients the benefit of making oxygen rather than storing it, which allows them to use electricity to charge batteries to use the concentrator when they travel from home.

Those advantages are tempered by other constraints on the system’s operation. The portable oxygen concentrators use the same technology as stationary oxygen concentrators only in smaller sizes. That means that the maximum oxygen produced and dosing of the oxygen differ by concentrator. Those two variables restrict the system, as the concentrator cannot make more oxygen than it was originally intended to produce. If the patient increases the demand with a higher dose setting or respiratory rate, either delivered dose, oxygen purity, or both will decrease. These limitations must be considered when prescribing and monitoring patients on this system.

Patient preference

With all of the new options for LTOT in the home, the main issue with equipment is clinical effectiveness. Many clinicians emphasize the equipment is not an end-point because of the significant variability in patient outcomes. Despite technical improvements, equipment remains merely a tool in the hands of knowledgeable clinicians. Until today’s technology demonstrates measurable benefits, payers and providers will continue to promote less-expensive systems to control costs.

Economics has driven product development. People using LTOT have become consumers rather than patients. They demand features and benefits targeted toward their preferences. For example, when a lightweight, portable LOX system became available, patients wanted this more expensive system even though many distributors did not. Patients got what they wanted by shopping for providers who carried the product. This same force continues to impact the sale of portable oxygen concentrators.

Looking to the future

The future of LTOT offers endless possibilities. Oxygen delivery systems need to address the dynamics of a patient’s oxygen requirement. An oxygen system with a feedback loop could monitor patients’ oxygen saturation and adjust to their oxygen needs.

Earlier disease detection and oxygen prescription could prevent the complications of chronic hypoxemia, which would require adequate oxygen delivery during sleep, exercise, and travel.

Patients who want to use their systems in public will need more practical and fashionable systems to meet their clinical requirement of oxygenation at all activity levels.

Robert McCoy, BS, RRT, FAARC, is the managing director of Valley Inspired Products Inc., Apple Valley, Minn., and also manages ValleyAire Home Respiratory Services Inc., a home medical equipment provider.