Final answer:
Elevated PVR or PVRI signifies increased resistance in the pulmonary circulation and is seen in conditions such as hypoxemia, acute lung injury, ARDS, pulmonary hypertension, and pulmonary congestion, often complicating respiratory and cardiac function.
Step-by-step explanation:
Pulmonary Vascular Resistance (PVR) or Pulmonary Vascular Resistance Index (PVRI) becomes elevated in various conditions affecting the lungs and heart. For instance, hypoxemia can lead to pulmonary vasoconstriction, which contributes to increased PVR. Similarly, conditions such as acute lung injury, acute respiratory distress syndrome (ARDS), pulmonary hypertension, and pulmonary congestion are associated with elevated PVR or PVRI.
These conditions often involve increased water and sodium as seen in heart failure, leading to pulmonary edema due to excessive leakage of fluid into lung tissues. Respiratory conditions like hypercapnia, where CO₂ levels are abnormally high, or hypocapnia, where CO₂ levels are abnormally low, can also have an effect on blood gas levels and subsequently on the resistance offered by pulmonary vessels.