Headache is one of the common causes of emergency department admissions and constitutes approximately 2%. Although the exact mechanism is not clear, It is known that high-flow oxygen therapy is effective in headache treatment. There are limited studies related to the use of oxygen therapy in headaches and its derivatives in the literature. In this study, the investigators aimed to compare the high and medium flow oxygen therapies with placebo in primary headache disorders.

Four different treatment methods were determined; 1) high-flow oxygen (15lt/min oxygen), 2) medium-flow oxygen (8lt/min oxygen), 3) high-flow room air as placebo (15 lt/min room air), 4) medium-flow room air as placebo (8 lt/min room air). All four treatment methods will be applied to all patients included in the study. One of the four treatments will be randomly applied at each separate ED admission with a gap of 1 week or more in between. This randomization will be performed by a computer at the time of admission. A study nurse will administer the patient's therapy according to the computer's current decision for 15 minutes. Patients and treating physicians will be blinded to the selected therapy. After 15 minutes of the end of treatment (at the 30th minute of the start of treatment), the treating physician will ask patients if they need rescue analgesia and analgesia will be administered if necessary. Additional analgesia is at the discretion of the treating physician. Patient data, including demographics, medical history, and findings of a physical examination performed before and after therapy will be recorded by the treating physician.

Inclusion Criteria:

• age 18-55 years
• frequent attacks of primary headache disorders according to International Headache Society (IHS) criteria

Exclusion Criteria:

• secondary headache disorders
• oxygen-dependent chronic illnesses such as chronic obstructive pulmonary disease
• a history of cerebrovascular disease
• pregnancy
• active smokers or living with a smoker.

all patients had one to six headache attacks per month which were started before 50 years old and were present for more than one year.