Last month, a soldier stationed for training at high altitude was urgently transferred to Southwest Hospital of Army Medical University, where we are based. Upon admission, he presented with chest tightness, difficulty breathing, and low blood oxygen saturation. CT angiography revealed that a thrombus had occluded a major pulmonary vessel, and he was diagnosed with acute pulmonary embolism. Following timely thrombolytic therapy, the soldier is out of danger.
In recent years, we have seen a gradual increase in cases of high-altitude-related pulmonary embolism. Because its symptoms resemble those of high-altitude pulmonary edema and the common cold, it is easily misdiagnosed. High-altitude pulmonary embolism is not a rare disease, yet it is a "silent bomb" threatening the health of officers and soldiers. Simply put, pulmonary embolism occurs when a thrombus formed elsewhere in the body "travels" to the lungs and blocks the pulmonary artery. Most thrombi originate in the deep veins of the lower limbs. When blood flow slows and becomes viscous, it tends to "clot" in the leg vessels. Once a clot breaks free and enters the pulmonary circulation via the bloodstream, it causes pulmonary embolism, which in severe cases can lead to sudden death.
The special high-altitude environment may accelerate thrombus formation. At high altitude, the air is thin; to compensate, the body produces more red blood cells, making the blood more viscous and slowing blood flow. Low temperatures cause vasoconstriction, further slowing blood flow and increasing the risk of thrombosis. The dry high-altitude climate accelerates breathing and increases water loss; if fluids are not replenished promptly, blood viscosity rises further. Research shows that the incidence of venous thrombosis at high altitude is more than 30 times that at lower elevations.
The symptoms of pulmonary embolism are sometimes atypical and can easily be mistaken for altitude sickness or pulmonary edema. The following signs must be taken very seriously: unexplained difficulty breathing or shortness of breath, worsening with activity; chest pain that worsens on inhalation, like a stabbing sensation; hemoptysis or blood-streaked sputum; rapid heartbeat, dizziness, or even syncope; unilateral calf swelling, pain, or tenderness on palpation (suggesting possible lower-limb thrombosis). If any of the above symptoms appear at high altitude, do not simply assume fatigue or a cold—report immediately to the military physician and undergo blood oxygen monitoring and physical examination as soon as possible. Early diagnosis is the key to successful treatment.
Scientific prevention of pulmonary embolism lies in daily habits. Drinking one more cup of water, moving for a few more minutes, and paying closer attention to abnormal signals from the body can prevent pulmonary embolism from occurring. Comrades are advised to remember the following four points during high-altitude garrison training:
"Water" (水). Adequate fluid intake keeps blood from becoming viscous. Everyone should proactively drink sufficient fluids—approximately 3 liters per day—without waiting until thirsty. Drink in small amounts frequently; plain boiled water or lightly salted water is preferred.
"Movement" (动). Prolonged sitting weakens the muscle-pump action of the lower limbs and causes blood stasis. It is recommended that after every hour of sitting, everyone stand up and move for 3 to 5 minutes, performing actions such as ankle dorsiflexion, toe raises, and marching in place. During sleep, elevating the lower limbs can promote venous return. When conditions permit, engage in moderate aerobic training daily to activate the calf muscle pump.
"Warmth" (暖). The temperature difference between day and night at high altitude is large; pay attention to keeping warm, especially the legs and feet. During nighttime rest, a hot-water bottle (take care to prevent burns) can be used to warm the lower limbs.
"Check" (查). Individuals with a history of thrombosis, lower-limb trauma or surgery, obesity, or polycythemia are at high risk for pulmonary embolism. Before entering high-altitude areas, they should undergo lower-limb vascular ultrasound examination and, if necessary, wear compression stockings or take prophylactic anticoagulant medication under the guidance of a military physician.