Final answer:
Pulmonary vascular resistance (PVR) is calculated using the PVR formula that incorporates pulmonary artery pressures and cardiac output, which is the amount of blood pumped by each ventricle per minute. Cardiac output's normal range is crucial to understanding and computing PVR. Oxygen and carbon dioxide exchange in the body is driven by pressure gradients in the veins and systemic tissues.
Step-by-step explanation:
The term Pulmonary vascular resistance (PVR) refers to the resistance offered by the pulmonary circulation. It is calculated using the formula PVR = (PAMP - PAWP) x 80/CO, where PAMP stands for pulmonary artery mean pressure, PAWP is the pulmonary artery wedge pressure, and CO is cardiac output. Cardiac output (CO) is a measurement of the amount of blood pumped by each ventricle in one minute, which equals heart rate (HR) multiplied by stroke volume (SV). A typical range for CO is 4.0-8.0 L/min, with a mean value of 5.25 L/min for each ventricle individually. Understanding CO is essential when assessing PVR as it directly influences the calculation.
Oxygen and carbon dioxide exchange in the body occurs down pressure gradients exemplified by venous Po₂ (partial pressure of oxygen in the veins) which is 100 mm Hg in the pulmonary veins, while venous PCO₂ (partial pressure of carbon dioxide) is 40 mm Hg. These values represent the condition as blood leaves the lungs and enters the systemic circulation. The blood's content changes as it interacts with systemic tissues, oxygen diffusing out and carbon dioxide diffusing in, reflecting the differing pressure gradients between blood and tissues.