Final answer:
Pulmonary embolism (PE) is a condition where a blood clot blocks the flow of blood to the lungs. It can be a serious and potentially life-threatening condition. High alveolar arterial gradient in a blood gas analysis can be indicative of PE.
Step-by-step explanation:
Pulmonary embolism (PE) occurs when a blood clot travels through the blood vessels and lodges in a pulmonary artery, blocking the flow of blood to the lungs. It can cause serious consequences such as lung damage or even death. In the case of a patient with a swollen leg, PE could be the cause if there is a high alveolar arterial gradient observed in the blood gas analysis.