This is a non-randomized phase 2 study designed to asses the mean flow velocity (MFV) and cerebral blood flow (CBF) response to non-invasive respiratory impedance.

Inclusion Criteria:

1. Age > 18 years
2. Ability and willingness to sign informed consent by patient or legally acceptable surrogate decision maker
3. Acute ischemic stroke within 72 hours of study enrollment
4. Imaging or examination confirming unilateral frontal lobe involvement in the stroke

Exclusion Criteria:

1. Hemorrhagic conversion of ischemic infarct

2. History or presence of congestive heart failure, as defined by any of the following:

   1. Any preceding diagnosis of congestive heart failure as per patient report or medical record
   2. Report of moderate or severe systolic or diastolic dysfunction on prior
   3. Reduced ejection fraction, <50%, on prior echocardiogram
   4. Jugular venous pulsations >10 cm
   5. Pulmonary edema on chest radiography Of note, an echocardiogram is not required prior to study enrollment.

3. History or presence of cardiomyopathy, as per medical record, patient report, or prior echocardiogram

4. History or presence of pneumothorax or hemothorax

5. History or presence of COPD

6. History of current use of home oxygen

7. Presence of pneumonia, as clinically determined by the primary medical team after admission chest radiography

8. Age < 18 years

9. Skull defect that would interfere with CBF monitoring

10. Pregnancy (urine or serum testing will required prior to enrollment of any pre-menopausal women)

11. Structural brain lesion, including known primary tumor, metastatic tumor, or vascular malformation

12. Prior neurosurgical procedure

13. Any medical condition that the clinical investigator feels would pose a hazard to the subject if he/she participated in the study