This study is a non-randomized, Phase 2 clinical trial designed to measure the cerebral blood flow (CBF) response to inhaled nitric oxide in acute ischemic stroke patients and healthy subjects. The monitoring is a 35 minute session during which cerebral hemodynamics will be monitored with both diffuse correlation spectroscopy (DCS) and transcranial doppler ultrasonography (TCD) while blood pressure, heart rate, cardiac output, respiratory rate, end oxygen saturation, and inhaled nitric oxide (NO)/nitrogen dioxide (NO2) concentration, are continuously monitored.

Inclusion Criteria:

Stroke Patients:

1. Age greater than 18
2. Acute ischemic stroke in the territory of the anterior, middle, or posterior cerebral artery, on either side of the brain
3. Study can be initiated within 72 hours of stroke symptom onset

3. Ability and willingness to sign informed consent

Healthy subjects:

1. Age greater than 18
2. Ability and willingness to sign informed consent

Exclusion Criteria:

Stroke subjects:

1. History of prior stroke or transient ischemic attack
2. Known cerebrovascular abnormality
3. History of congestive heart failure
4. Presence of pneumonia or active pulmonary infection
5. Current use of any NO donor medication (sodium nitroprusside or nitroglycerin)
6. Age less than 18 years
7. Skull defect that would interfere with CBF monitoring
8. Pregnancy
9. Structural brain lesion
10. Prior neurosurgical procedure
11. History of psychiatric disease
12. Any medical condition that the clinical investigator feels would pose a hazard to the subject if he/she participated in the study

Healthy subjects:

1. History of any neurological disease
2. History of stroke or transient ischemic attack
3. Known cerebrovascular abnormality
4. History of congestive heart failure
5. History of chronic pulmonary disease such as asthma or chronic obstructive pulmonary disease
6. Presence of pneumonia or active pulmonary infection
7. Current use of any NO donor medication (sodium nitroprusside or nitroglycerin)
8. Age less than 18 years
9. Skull defect that would interfere with CBF monitoring
10. Pregnancy (urine or blood tests will not be performed)
11. Structural brain lesion
12. Prior neurosurgical procedure
13. History of psychiatric disease
14. Any medical condition that the clinical investigator feels would pose a hazard to the subject if he/she participated in the study
15. Cognitive impairment