The brain is such a metabolically active organ that it consumes about 20% of oxygen burned every minute by an average adult even though it only contributes about 2% of the body weight. As a result, the brain produces a disproportionately high amount of CO2 every minute in comparison with the rest of the body.

The researcher can use Diffuse Optical Spectroscopy Imaging, cerebral non-invasive oximetry instrument, to determine cerebrovascular reactivity during surgery procedure. Specifically, the cerebral tissue O2 saturation can measure by Diffuse Optical Spectroscopy Imaging can use for cerebral blood flow in the evaluation of cerebrovascular reactivity.

Adequate brain perfusion is critical not only to supply oxygen and nutrients but also to wash out metabolic end products including CO2. Blood flow depends on perfusion pressure and vascular bed resistance. It is well known that multiple physiological and pathological factors affect cerebral vasculature, and the resistance to blood flow. The cerebrovascular responsiveness to those factors determines how well the brain can maintain and adjust its perfusion.

Inclusion Criteria:

1. Male or Female 20 years of age and older
2. Female non-pregnant
3. Subject scheduled for elective surgery under general anesthesia with intubation.
4. Subject who is able to give informed consent.

Exclusion Criteria:

1. Less than 20 years old of age
2. Pregnant woman
3. Subjects currently diagnosed with severe hypertension, myocardial ischemic disease, symptomatic valvular disease(s), symptomatic arrhythmia, uncompensated congestive heart failure, intracranial aneurysm.

Elective surgery