In this study, the concentration of hemoglobin within the subject's blood will be reduced in a controlled manner by administering fluids intravenously. The accuracy of a noninvasive hemoglobin sensor(s) will be assessed by comparison to hemoglobin measurements from a laboratory analyzer.

Inclusion Criteria:

• Male or female
• 18-40 years of age
• Weight of at least 110 lbs and less than 250 lbs or a BMI under 36 for subjects taller than 6 feet.
• Physical status of ASA I of II
• Able to read and communicate in English
• Has signed written informed consent
• Female, non pregnant. Female subjects will be provided with a pregnancy test free of charge.

Exclusion Criteria:

• Age less than 18 yrs and greater than 40 years
• Weight of less than 110 lbs or more than 250 lbs. or a BMI of 36 or greater for people over 6 feet tall.
• Hemoglobin less than 11 g/dL
• ASA physical status of III. IV, V.
• Pregnant
• Subject has known drug or alcohol abuse
• Subject has skin abnormalities affecting the digits such as psoriasis, eczema, angioma, scar tissue, burn, fungal infection, substantial skin breakdown, nail polish or acrylic nails.
• Subject has experienced a head injury with loss of consciousness within the last year.
• Subject has known neurological and psychiatric disorder that interferes with the subjects' level of consciousness.
• Known or concurrent chronic usage of psychoactive or anticonvulsive drugs within the last 90 days, or any use in the last 7 day (i.e. tricyclic antidepressants, MAO inhibitors, Lithum, neuroleptics, anxiolytics or antipsychotics, except SSRIs).
• Subject has any medical condition which in the judgment of the investigator, renders them inappropriate for participation in this study, such as Reynauds Syndrome.
• Systolic BP >140 mmHg or Diastolic BP > 100 mmHg.
• Baseline heart rate < 50 bpm.
• Inability to tolerate sitting still or minimal movement for up to 90 minutes
• Discretion of investigator