By George H. Sands, M.D.
Beth Israel Medical Center
New York, New York
Oxygen treatment of headaches was first mentioned in literature in 1939. Mr. Charles E. Rhein, Linde Air Products Co., reported to Dr. Alvarez at the Mayo Clinic in Rochester, MN the successful treatment of severe "migraine" attacks by breathing pure oxygen. Subsequently, Dr. Alvarez noted that the treatment with 100 percent oxygen at a flow of six to eight liters a minute would often produce relief. Sometimes patients would not be able to obtain relief with this treatment, whereas at other times they would. In 1940, Dr. Alvarez reported the treatment of over 100 persons suffering from headache attacks. They were treated with oxygen with a nasal type of mask and a flow of six to eight liters a minute. He found that 80 percent of "migrainous" headaches were completely or significantly relieved. Dr. Alvarez also found that patients with other types of headaches were often helped through the use of oxygen inhalation and that the prompt institution of therapy had a better chance of resulting in relief than if it was delayed. This work was much less rigorous than that done recently.
The first significant work done on oxygen inhalation was that of Dr. Kudrow who investigated patients with cluster headaches. Fifty-two out-patients were treated with 100 percent oxygen at a flow of seven liters per minute. 75 percent of these patients had "complete or almost complete cessation of head pain within 15 minutes: for at least seven of 10 attacks." Dr. Kudrow found that there is greater effect of oxygen inhalation in patients with episodic cluster. Patients younger than 50 years of age appeared to have a better response than those above age 50. However, this was not considered statistically significant. Also of interest was that 62 percent of those responding to oxygen had their attacks relieved within seven minutes of starting therapy. Dr. Kudrow did a second trial in a crossover fashion, comparing sublingual ergotamine tartrate and oxygen inhalation in the abortive treatment of cluster headache. Fifty patients selected at random used either 100 percent oxygen or the ergotamine to treat their headaches. After 10 cluster headaches were treated with one modality the patient then used the other treatment for 10 headaches. Eighty-two percent of the subjects found at least seven out of 10 cluster headaches were successfully relieved by the oxygen, while 70 percent treated their headaches successfully with ergotamine. These results were not considered statistically different.
Dr. Fogan studied 19 patients with cluster headache in the most rigorous fashion possible through a double-blind crossover study comparing oxygen versus air inhalation. He found there was a significant difference in the relief obtained in those patients inhaling oxygen versus air. By making this comparison Dr. Fogan was able to be sure that the oxygen was the significant factor in successfully treating the cluster headaches. He eliminated the other associated factors involved with the inhalation of a gas, such as the gas tank and the oxygen mask.
The way in which oxygen inhalation reduces headache pain is unknown. Researchers have shown that there is an increased blood flow in the brain in both cluster and migraine headaches, although both headaches do not have the same degree of increased flow. It has been shown that oxygen causes a marked decrease in cerebral blood flow that is coincident with the reduced degree of pain in cluster headache.
While it is clear that oxygen is a very useful therapy in cluster headaches, its utility in migraine headaches is less well documented. It is unlikely that the literature of the 1930s and 1940s was able to distinguish between migraine and cluster headaches. Thus, any belief ascribed to migraine headaches in that era could have confused patients with cluster headaches with those of migraine headaches. Some investigators have found it useful, however, to use oxygen therapy in patients with migraine headaches. I have found approximately 50 percent of my patients with migraine headaches will be able to achieve some relief with oxygen therapy. They use 100 percent oxygen for eight to nine liters a minute for up to 30 minutes. If no effect has been achieved by that time, it is unlikely that one will occur.
The side effects of oxygen inhalation are rare. Cluster headache patients are very often smokers and if one should happen to light up while an oxygen tank is open, the result can be explosive. Another side effect of oxygen use was found by Dr. Kudrow who noticed that 25 percent of his study patients had rebound cluster headaches after oxygen inhalation therapy. No other side effects have been found and therefore, oxygen therapy is safe. Oxygen could be preferred to ergotamine's use since ergotamine often causes nausea and vomiting as well as a sense of unreality and leg cramps. Ergotamine cannot be used in patients with hypertension, peripheral vascular disease or infections when oxygen obviously can be. It has been suggested that oxygen therapy when used together with ergotamine will give greater relief than the sum of the effect found by using either one alone.
Oxygen therapy is not a well-known modality for headache patients. Many physicians are unaware of the benefits of oxygen therapy, as are third-party payers who hesitate to reimburse for its use. Sometimes this can be overcome by a letter from the treating physician. Since approximately 50 percent of patients respond to oxygen therapy, it is worth trying it before going to the expense and effort of having an oxygen tank installed in one's home.