The investigators hypothesize that changes in blood circulation can be reflected by exhaled CO2 provided CO2-production in the tissues and ventilation from the lungs are stable. The investigators want to explore changes in cardiac output (the amount of blood being pumped out of the heart each minute) in patients using different devices: an esophagus ultrasound device measuring cardiac output, a finger cuff measuring blood pressure and cardiac output, and exhaled carbondioxide in the patients' breath measured by the ventilator.

The investigators investigate patients after bypass surgery or heart valve replacement, and induce changes in cardiac output with passive leg raise or ventricular pacing.

Measurements with the finger cuff (pulse contour analyses) were aborted due to technical difficulties.

Inclusion Criteria:

• Persons 18 years or older scheduled to undergo arteriocoranary bypass surgery or aortic valve replacement.

Exclusion Criteria:

• Esophageal pathology, EF <40%

No plan to share individual participant data.