A Brief History of Oxygen Therapy, Part 2 Print E-mail



In the 1950s, intensive research on oxygen therapy for COPD patients was carried out on both sides of the Atlantic. These early studies showed that certain COPD patients seemed to improve in many waysespecially in their exercise tolerancewhen they breathed pure oxygen instead of room air. But for some time, researchers could not find evidence of actual physiological change underlying these apparent benefits.

Two studies in the mid-1960sone in Denver, Colorado, and one in Birmingham, Englandplaced the use of oxygen on more scientifically solid ground. They found that:

Physiologic exercise tolerance increases.

Constriction of the lungs' blood vessels caused by chronically low oxygen disappears, taking a great load off the heart, which then functions more effectively.

Performance improves on a variety of neuropsychiatric tasks, for example: attention span, verbal ability, abstract ability, simple sensory and motor skills, complex perceptual and motor skills, and memory. In other words, the brain works better.

Oxygen had obviously improved the level of functioning of the patients who had been tested. But several important questions remained to be answered. First: in these two studies, each patient's responses to added oxygen were compared with his earlier responses, instead of with a similar patient who was not getting extra oxygen. Researchers could not know if someor mostof their improved exercise tolerance and neuropsychiatric performance were due to receiving the special attention research subjects get. These studies had to be repeated, using matching patient groups. They would receive that same attention and testing, but only one would be given extra oxygen to breatheand none of the patientsor the testerswould know which patients were getting oxygen and which weren't. Second: how many hours should a patient spend on oxygen for maximum benefit? Third: since oxygen is a drug, and so cannot be totally free of side effects, how can we clearly identify those patients who need oxygen?

Development of easily portable oxygen containers in the late 1970s made possible the two large-scale, three-year studies that would answer these questions. The Nocturnal Oxygen Therapy Trial (NOTT) in the United States was supported by the National Institutes of Health. The British Medical Research Council supported a similar study in the United Kingdom. Patients chosen for these studies showed chronic symptoms of seriously inadequate oxygen (very low arterial blood oxygen, evidence of cor pulmonale, and/or too many red blood cellspolycythemia). Each study divided these hypoxic patients into two groups. In the American study, one group breathed extra oxygen only during sleep (because oxygen reaches its lowest levels then), while the other breathed it 24 hours a day. In the English study, one group breathed extra oxygen 15 hours a day. The other group had no extra oxygen at all.

The most striking conclusion was that extra oxygen improves survival. Remember thatat the startall the participating patients had severe COPD. When the studies ended three years later: 75% of the patients getting oxygen 24 hours a day were still alive; 50% of the two part-time oxygen groups were still alive; and only 35% of those without any extra oxygen had not died.

Continuous extra oxygen is more effective than part-time use for at least two reasons. First, removing the burden of inadequate oxygen on the heart and lungs day and nightinstead of only during sleepmore substantially prolongs the capacity of these organs to function reasonably well. Second, the availability of an easily portable daytime oxygen supply enables these patients to get around much more than they had been able to in quite some time. They resume activities at home and outside, including participation in a pulmonary rehabilitation program. Increased physical activity, plus the rehabilitation program, improve physical tone and stamina, overall health and productivity, and are emotionally and psychologically rewarding.


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