Stroke Oxygen Study


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. We recently completed a pilot study of the effect of oxygen treatment during the first 72 hours after a stroke which suggested that oxygen could improve neurological recovery at 7 days and may reduce the level of disability at 6 months. The pilot study included 301 patients and was not large enough to show clinical benefits, but helped us to design this study. The Stroke Oxygen Study (SO2S) will enrol a much larger number of participants to confirm or exclude a definite benefit from oxygen treatment.

SO2S will recruit 6,600 patients from over 100 hospitals throughout the UK. Adult patients who have had a stroke within the last 24 hours before hospital admission will be eligible, if they have been in hospital for no longer than 24 hours and if, in their doctor’s view, they have no indications for or against oxygen treatment. Patients will be given information about the trial and included if they agree to take part and fit the inclusion criteria.

Participants will be 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

The trial treatment will be started immediately after allocation. If a reason for starting oxygen, increasing or decreasing the dose develops while the patient is on the study, treatment will be given as clinically indicated, irrespective of trial group.

Outcomes will be 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 will assess how well the patient has recovered by doing a standardized neurological examination and comparing the results with those on admission. The questionnaires will examine subsequent recovery by asking standard questions shown to be reliable in assessing stroke outcome. These will include how well the patients have recovered from the stroke, quality of life, the ability to perform simple activities of daily living (e.g. washing, dressing, walking) and extended activities of daily living (e.g. cooking, shopping, driving). In addition to clinical outcomes we will also collect data which allow us to make a health economic assessment of the costs and benefits of routine oxygen treatment.

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.