If unexplained shortness of breath, pleuritic chest pain, tachycardia, and decreased oxygen saturation occur, one should be highly vigilant about pulmonary embolism. Generally, pulmonary embolism has no direct relationship with pneumonia. High-risk factors for pulmonary embolism include obesity, prolonged immobilization, stroke, congestive heart failure, malignant tumor, inflammatory bowel disease, lower limb fracture, anesthesia time exceeding 30 minutes, and acquired or genetic hypercoagulable state. It usually manifests as difficulty breathing, rapid breathing, and pleuritic chest pain.