The use of ambulatory supplemental oxygen has been around for much longer than you might think. In fact, we can go all the way back to 1959 when Alvan Barach, MD, published his pioneering work titled “Ambulatory oxygen therapy: Oxygen inhalation at home and out of doors.”1 We have come a long way in the past 50 years. Huge strides have been made in understanding the physiology of the body’s use of oxygen. At the same time, oxygen equipment and the related technology have evolved at a breathtaking pace.

Today we have available a variety of small, lightweight systems under 10 pounds, and, with oxygen-conserving devices extending duration, these have become the standard for ambulatory oxygen.2 Whether small compressed oxygen tanks, liquid oxygen portables, or battery-powered portable oxygen concentrators, these devices are opening up new and exciting possibilities for chronic respiratory patients. There are more and more referrals to pulmonary rehabilitation (PR) of patients who are already on long-term oxygen therapy (LTOT) and also patients who are not currently on home oxygen but would benefit from supplemental oxygen during exercise and activity.

To help understand the role of supplemental oxygen in PR, let’s begin with the American Thoracic Society/European Respiratory Society definition3:

“Pulmonary rehabilitation is an evidence-based, multidisciplinary, and comprehensive intervention for patients with chronic respiratory diseases who are symptomatic and often have decreased daily life activities. Integrated into the individualized treatment of the patient, pulmonary rehabilitation is designed to reduce symptoms, optimize functional status, increase participation, and reduce health care costs through stabilizing or reversing systemic manifestations of the disease. Comprehensive pulmonary rehabilitation programs include patient assessment, exercise training, education, and psychosocial support.”

Denise Heitzman crossing the finish line in a 5k run in Santa Cruz, Calif; 6 lpm O2 from a tank that is in the “baby” stroller keeps her running.

Can the use of supplemental oxygen during PR exercise training “reduce symptoms” and “optimize functional status” and “increase participation”?

The experienced respiratory care professional would answer “Yes” without hesitation, but, in today’s world, spending precious dollars (especially tax payer dollars) on any and all forms of health care is sure to be closely questioned. We have the obligation to examine the evidence and make the case for using supplemental oxygen based on strong evidence and objective data.

Reducing Symptoms and Optimizing Functional Status

In acute care, respiratory professionals daily see the beneficial results of placing a hypoxic patient on oxygen: the decreased work of breathing, decreased respiratory rate, decreased anxiety, improved color, and improved cognition. In PR, we are tasked with conducting exercise training of the stable chronic respiratory disease patient who is usually very deconditioned and often hypoxemic.

Over the past few years, many studies have been done to explore the benefits of using supplemental oxygen during exercise training. The 2005 ATS/ERS Statement on Pulmonary Rehabilitation4 summarized it well:

“Oxygen supplementation during pulmonary rehabilitation, regardless of whether or not oxygen desaturation during exercise occurs, often allows for higher training intensity and/or reduced symptoms in the research setting.”

Pulmonary rehabilitation is often thought of as a treatment for COPD, but we are seeing restrictive disease patients referred to PR in ever-increasing numbers. A 2002 study5 that focused on cystic fibrosis patients again confirmed the benefits of supplemental oxygen:

“Results indicate that supplemental oxygen improves submaximal exercise in patients with moderate-to-severe cystic fibrosis. Oxygen therapy may be an important intervention to improve participation and maximize the benefits of pulmonary exercise rehabilitation programmes.”

Real World Clinical Practice

So, how does this all translate into clinical practice, ie, conducting PR exercise in the real world?

Hypoxemia at rest. Many PR patients have identified resting hypoxemia and are already on home O2. They should already have an ambulatory system when referred. Often these patients will have been supplied with an E cylinder as a “portable” system.

There is an issue here worth discussing: Please note that an E cylinder on a wheeled cart is not an ambulatory oxygen system. In 1999, the 5th Oxygen Consensus Conference defined an ambulatory oxygen system as follows: “Ambulatory—Available for daily use, carried by the patient, weighing less than 10 pounds, minimum oxygen duration of at least 4-6 hours, a 2 lpm continuous flow or equivalent.”6

Peter M. Wilson, PhD, takes it a step further, calling for “5 x 5” portables: “First of all, consider portables that weigh less than 5 pounds and have a duration of more than 5 hours. These portables are light enough to be carried by most people. Heavier portables, weighing more than 5 pounds, are too heavy to carry and, for long distances, should be transported in a carrier. Let us also consider portables that have durations of 5 hours or more. Those with less than 5 hours duration will run out during extended shopping at the mall or a sightseeing excursion.”7

Decreased Medicare reimbursement for durable medical equipment oxygen suppliers has resulted in a trend back to the old +20 pound E cylinders with a cart. As health care professionals, we need to advocate for our patients by citing Wilson’s definition as the standard of care and insisting on true ambulatory systems.

The patient with resting hypoxemia will desaturate to some degree with exercise or increased activity. The question is, how much? As with all PR patients, early and thorough assessment is the key. A 6-minute walk test (6 MWT) usually results in a greater degree of desaturation than the low level to moderate intensity exercise typical of PR. This allows the PR clinician to anticipate the need to increase O2 lpm flow and/or to switch from an oxygen-conserving device (OCD) to continuous flow. The 6 MWT should always be done according to a written procedure for reproducibility and validity. I recommend following, as closely as possible, the ATS Statement: Guidelines for the Six-Minute Walk Test.8 In any case, every PR program should have a written policy and procedure for their own facility’s 6 MWT.

Another very helpful tool is the Borg 10 point scale, which may be used to assess perceived level of dyspnea (PLD) and perceived level of exertion (PLE). It should be used during the 6 MWT8,9 and during exercise sessions. Once the patients become comfortable with scoring themselves, the Borg scale provides them with a simple no-cost way to self-monitor during exercise and activity.

Exercise, especially beginning exercise, should be monitored by continuous oximetry, if available, or frequent spot checks so that O2 may be titrated appropriately. The goal should be to maintain Sao2 at or above 90%.10 Oxygen flow may need to be adjusted and/or changed from OCD to continuous to keep the saturation >90%. Some patients will desaturate below 90% even with increased O2 delivery. With guidance from your PR physician medical director and your PR policy and procedure manual, you may choose to 1) terminate the exercise; 2) reduce the exercise intensity; or 3) continue if the exercise is being otherwise tolerated. Exercise should not be continued if the Sao2 remains below 88% after increasing the lpm flow, reducing exercise intensity, and actively coaching the patient’s breathing techniques.

James Warren into the weight work aided by 4 lpm O2

Normoxic at rest. Some PR patients have a resting Sao2 above 90% on room air, but show some degree of desaturation with exercise or activity. These patients may already have an ambulatory O2 system if the desaturation with exercise or activity was identified prior to PR. Your assessment and the 6 MWT may be the first time the need for oxygen is identified, however. Although these patients tend to be at a higher functional level (than the hypoxic at-rest patient), the same criteria for an ambulatory O2 system mentioned earlier still apply: E cylinders with carts are not ambulatory oxygen systems.

Again, monitoring with continuous or frequent oximetry is essential and the goal is to maintain Sao2 >90%. Oxygen flow should be titrated and/or modality changed as needed to keep the Sao2 >90%.

Some patients with moderate or even severe COPD do not experience significant desaturation during exercise. Can these patients benefit from oxygen during exercise? The research team at Harbor-UCLA Rehabilitation Clinical Trials Center in Torrance, Calif, set out to answer that question. In 2003, they published a very convincing study11 in which the authors stated: “We conclude that supplemental oxygen provided during high-intensity training yields higher intensity and evidence of gains in exercise tolerance in laboratory testing.”

Further studies are needed to confirm and expand on these results, but an interesting door has been opened. There may be real physiological benefits to using supplemental oxygen during exercise even in the absence of hypoxemia.

One of the primary goals of PR is for the patient to have an exercise plan that is safe and effective for them to continue at home or in the community. That home exercise plan must include what lpm flow settings to use and when, whether continuous flow is needed or an OCD is adequate, and how to self-monitor for signs of hypoxia. Use of the Borg to help the patient self-monitor should be reinforced during every exercise session.

The cost of finger oximeters has decreased so dramatically that some patients are choosing to purchase their own. In these cases, the PR clinician should provide repeated instruction and guidance to ensure the patients understand what the readings mean and how to use the information.

As the patient progresses through PR, the possible need to adjust lpm flow, change modality, and even to change to a different delivery system will usually become apparent. By the end of PR, usually 8 to 12 weeks of visits two to three times per week, the patients and their family members or spouses should be confident and comfortable with self-managing their oxygen equipment.

Finally, ambulatory oxygen can play a major role in improving health-related quality of life (HRQL). This was documented by a well-designed 2002 study12 comparing oxygen and air. “The major finding of the randomized, controlled double-blind study was improvement in HRQL with ambulatory O2 compared to cylinder air in dyspneic COPD subjects with exertional desaturation.”

The ultimate goal of pulmonary rehabilitation is an improved quality of life for individuals living with chronic respiratory disease. Adding supplemental oxygen to the mix can result in better outcomes to the benefit of both patients and their families.

Carl Willoughby, RRT, RCP, is pulmonary rehabilitation coordinator, Mad River Community Hospital, Arcata, Calif. For further information, contact [email protected]


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