In acute state of ischemic stroke，if patients with sleep apnea hypopnea syndrome may need additional respiratory management such bi-level positive airway pressure.We supposed the patients with stroke can take benefit of functional recovery form bi-level positive airway pressure. We choose the patients who suffered ischemic stroke in 48 hours ，then evaluate the respiratory status. Stroke patients who were diagnosed as sleep apnea hypopnea syndrome will accept additional treatment with bi-level positive airway pressure for 7 night（per night 6 hours）.Then the modified Rankin scale score and NIHSS will be recorded at 30 days and 90 days after stroke.