Patients with pulmonary embolism primarily suffer from emboli within the venous system, which travel back to the right heart and then become lodged in the pulmonary artery, forming a pulmonary artery thrombus. This reduces pulmonary blood flow and impacts the exchange of air in the lungs, leading to hypoxia in the patient. Following hypoxia, the brain tends to enter a sleepy state, thus many patients with pulmonary embolism exhibit sleepiness. This sleepiness is related to the pathophysiological mechanisms of pulmonary embolism. At this point, it is crucial to provide sufficient oxygen to the patient to address their hypoxemia. Ultimately, the most fundamental treatments are prompt thrombolysis or anticoagulation therapy to resolve the embolus, addressing the condition fundamentally.