Registered Cardiovascular Invasive Specialist (RCIS) Practice Test

What is the cardiac output of a patient with an arterial O2 saturation of 98%, pulmonary artery O2 of 74%, RV O2 saturation of 71%, hemoglobin of 14.7, PCWP of 12, O2 consumption of 250 ml/min, and a constant of 1.36?

1. 4.4 L/min

2. 5.2 L/min

3. 6.0 L/min

4. 3.9 L/min

The correct answer is: 5.2 L/min

To determine the cardiac output in this scenario, we use the Fick principle. The Fick equation that relates oxygen consumption (VO2), arterial oxygen content (CaO2), venous oxygen content (CvO2), and cardiac output (CO) is given by: \[ CO = \frac{VO2}{(CaO2 - CvO2)} \] In this case, we need to calculate the arterial and venous oxygen contents. The arterial oxygen content can be approximated using the formula: \[ CaO2 = (1.34 \times hemoglobin \times SaO2) + (0.003 \times PaO2) \] Where: - Hemoglobin is the concentration of hemoglobin in g/dL. - SaO2 is the arterial oxygen saturation. - PaO2 is the partial pressure of oxygen in arterial blood (not provided directly but can often be estimated). The venous oxygen content can be calculated similarly: \[ CvO2 = (1.34 \times hemoglobin \times SvO2) + (0.003 \times PvO2) \] Where: - SvO2 is the mixed venous oxygen saturation, typically sampled from the pulmonary artery. Given the values