Hypoxemia is common in acute ischemic stroke and associated with neurological deterioration and mortality. However, the benefit of oxygen therapy is controversial. Severity of stroke may affect the benefit of oxygen supplementation. Abnormal breathing patterns are commonly found among stroke patients and may increase the risk of hypoxemia. High flow nasal cannula (HFNC) has several advantages from controllable fraction of inspired oxygen (FiO2), reduction of nasopharyngeal resistance and positive end expiratory pressure effect. In this study, we aimed to assess the therapeutic effect of HFNC on oxygen desaturation index (ODI) and neurological outcomes in stroke patients with moderate and severe severities, compared with no and low flow oxygen supplementation.

Inclusion Criteria:

1. Age of 18 or more
2. Clinical and radiographic findings including computerized tomography of brain compatible with acute ischemic stroke
3. Presentation within 72 hours after the stroke onset
4. National of Health Stroke Scale (NIHSS) of 5 or more,
5. Limb weakness defined as motor power grade of 4 or less,
6. Able to give informed consent, or the next of kin was willing to give assent

Exclusion Criteria:

1. Recognized indications for oxygen treatment, such as oxygen saturation on room air of less than 92%, acute left ventricular failure, severe pneumonia, pulmonary emboli, and chronic respiratory failure treated with home oxygen supplementation
2. Recognized contraindications for oxygen treatment including chronic hypercapnia and type II respiratory failure
3. Subjects with previous diagnosis of obstructive sleep apnea (OSA) or highly suspicious of OSA, screened by STOPBANG score of 5 or more