The goal of this observational study is to find out if researchers can measure oxygen consumption in the body without having to draw blood from lines in arteries and central veins.

Participants will undergo measurements of arterial blood oxygen saturation using both finger and neck pulse oximeters.

TOUCAN-1 is a study to estimate the accuracy and precision of pulse oximetry as a noninvasive tool for oxygen consumption measurement. Researchers will use a pair of commercially-available, noninvasive pulse oximeters to estimate the oxygen saturation of blood in the internal jugular vein, and compare it to the directly measured oxygen saturation in sampled jugular blood. Researchers will then measure the arterial oxygen saturation in a finger, and compare it to the directly measured oxygen saturation in sampled radial arterial blood.

Inclusion Criteria:

• Inpatient at the University of Wisconsin University Hospital
• Has an internal jugular venous central line
• Has a radial arterial line

Exclusion Criteria:

• Currently receiving extracorporeal membrane oxygenation (ECMO)

• Currently receiving continuous renal replacement therapy (CRRT/CVVH)

• All usable lumens of the participant's jugular catheter are in use, and interruption of any medical or therapy through any lumen would, in the view of the primary care team, compromise the participant's care.

• Jugular venous catheter is not functional or position is not confirmed by radiography

• Arterial cannula is not functional

• Known history of sickle cell anemia or other hemoglobinopathy

• Therapy with any of the following medications:

  • Nitroprusside
  • Hydroxocobalamin
  • Indocyanine green
  • Norepinephrine
  • Vasopressin
  • Epinephrine
  • Any other medication or therapy that, in the judgement of the study investigators, may affect the accuracy and precision of the noninvasive oximetry results

Intensive care patients who already have internal jugular vein and radial artery catheters in place as part of routine clinical care.