1996 OPEN FORUM Abstracts
Oxygen Therapy in COPD
Brian L. Tiep, MD Sunday, November 3, 1996
Long term oxygen therapy (LTOT) improves mortality, morbidity and quality of life in hypoxemic patients with COPD. Recently LTOT has been demonstrated to also improve skeletal muscle metabolism and increase the energy index. The physiological goals of LTOT are to reverse or prevent tissue hypoxia and its disastrous consequences. For best results oxygen should be administered continuously. However, oxygen therapy is inconvenient, unsightly, expensive and lacks in portability and availability particularly for the large population of hypoxemic COPD patients. The lessons of pulmonary rehabilitation have taught that patients should be encouraged to be active and participate in life; likewise oxygen systems should be portable.
Portability has been successfully addressed via smaller and lighter weight containers with high storage capacities and by devices that maximize the efficiency of oxygen delivery. The storage containers come in the form of smaller liquid oxygen canisters and high pressure gas cylinders. Unfortunately, despite some valiant attempts, oxygen concentrators have not been made light enough or efficient enough to become portable alternatives to either gas or liquid. Three categories of oxygen conserving devices, reservoir cannulas (Oxymizer and Pendant), transtracheal catheters and demand pulsing devices improve the efficiency of oxygen delivery by providing it mainly during early inhalation when it can participate in alveolar-capillary gas exchange. This improves portability and range from home. Transtracheal catheters have additional benefits including better cosmetic acceptability and reducing minute ventilation. Even the carrying systems have improved with many patients able to carry their oxygen in fanny packs and pocketbooks. Some of these devices are expensive but they more than pay for themselves by reducing the frequency of oxygen service to the home. The small systems support the cosmetic advantages of transtracheal oxygen as they render the oxygen supply less noticeable.
The physiological and Medicare reimbursement guidelines that qualify a patient for long term oxygen relate to the patient's diagnosis and documentation of hypoxemia. However, there are gray areas, such as administering oxygen to improve exercise performance in normoxemic COPD patients or relieve dyspnea. The physiologic goals of oxygen therapy are to reverse or prevent tissue hypoxia under the various conditions of life including wakeful rest, sleep and exertion. Accordingly, the patient's oxygen prescription should be directed toward meeting those physiological goals.
Recent advances associated with pulmonary rehabilitation have also been complementary to LTOT. Exercise physiologists have improved our knowledge of the benefits of exercise and its relationship to oxygen delivery, uptake and utilization. The combination of small oxygen systems and exercise training for the patient with exercise hypoxemia has led to potent therapeutic reversal of the disability of chronic lung disease. These advances will enable more patients to travel including air travel. Airlines and other transportation carriers are beginning to understand the use of oxygen in its various forms and are better able to provide oxygen for the active and mobile patient.