Stroke Oxygen Study

Summary

Stroke is a common and disabling condition and there is a need to find out more about how to treat patients early after the stroke. Breathing problems frequently occur, and blood oxygen levels often fall below normal. Such falls can easily be missed, especially at night, and are clinically significant. Patients with low oxygen levels are less likely to recover well. Routine oxygen treatment could prevent low blood oxygen levels and subsequent worsening of the brain damage.

Oxygen is used widely in hospitals and in ambulances throughout the UK. It is a safe and well established treatment. The main adverse effect is that attachment to the oxygen tubing will restrict mobility. This may be less of a problem if oxygen is given at night only. Since stroke patients are most likely to have low blood oxygen levels at night restricting oxygen treatment to night only may provide oxygen when it is most needed without interfering with rehabilitation. Since oxygen can be given safely to most stroke patients, is cheap and easily available, even small longer-term improvements in outcome will result in significant gains in health and quality of life.

SO2S has enrolled 8,003 patients from over 100 hospitals throughout the UK. Adult patients who had no indication for oxygen treatment to be given and who had a stroke within the last 24 hours before hospital admission were eligible to participate.

Participants were allocated randomly to one of 3 treatment groups:

Group 1: usual clinical care, oxygen is given when clinically required

Group 2: oxygen treatment overnight for 3 nights

Group 3: continuous oxygen treatment for 72 hours

Outcomes were assessed by a member of the research team at the hospital at one week and by postal questionnaire at 3, 6, and 12 months. At one week we assessed how well the patient had recovered by doing a standardized neurological examination and comparing the results with those on admission. The questionnaires examined subsequent recovery by asking standard questions shown to be reliable in assessing stroke outcome. These included how well the patients recovered from the stroke, quality of life, the ability to perform simple activities of daily living (e.g. washing, dressing, walking), extended activities of daily living (e.g. cooking, shopping, driving), and outcomes considered particularly important by a patient and carer focus group (sleep, eyesight, speech, and memory.

The results of the stroke oxygen study show that giving oxygen to stroke patients with normal blood oxygen levels does not improve outcome.

This means that it is not necessary to give oxygen routinely to stroke patients who have no breathing problems.

Patients who have low oxygen levels or breathing problems were not included in the study and should be given oxygen as needed.

The results are important, because they allow us to stop giving oxygen, when not needed. They also made us focus on causes of low oxygen levels. Our next study is looking at methods of preventing pneumonia, a major cause of death after stroke.