OVERVIEW
Currently, mixed chronic mountain sickness (mixed chronic mountain sickness) is a chronic highland disease that is characterized by both hypoxic erythropoietic hyperplasia and highland heart disease due to pulmonary arterial hypertension. Mixed chronic mountain sickness mostly occurs in the plains migrants who have lived in the plateau for a long time and a few people who have lived in the world, and the incidence is generally higher in men than in women, and it is rare in children. It has been reported that the prevalence of the disease is significantly higher in people living in the Andean highlands of South America than in those living in the Himalayan region, and it has been hypothesized that this may be related to the fact that the population has lived in the Himalayan region longer than in the Andean highlands.
Etiology
Mixed chronic altitude sickness is common in people who have been living in the highlands above 3500 meters above sea level for a long time. The etiology is mostly associated with high altitude (≥3500m). In addition, smoking, obesity hypoventilation syndrome, and sleep apnea disorders are also important predisposing factors for the development of hypoxemia in highlanders.
Symptoms
The most common symptoms of this disease are headache, dizziness, abnormal sensation, memory loss, sleep disorder including insomnia or drowsiness, loss of appetite, and reduced exercise tolerance.
Tests
1. Blood tests
In routine blood test, the number of red blood cells and hemoglobin concentration in peripheral blood are elevated. The total number and classification of white blood cells are within normal range, and platelets are the same as those of healthy people at the same altitude. Bone marrow granulocyte system was mainly characterized by exuberant proliferation of erythroid cells, with erythroid cells occupying 33.3% of the nucleated cells, which was obvious in middle and late juvenile erythroid cells. The granulocyte and megakaryocyte systems showed no significant changes. Arterial blood gas analysis of acidity and alkalinity (pH) measured decreased pH. Blood gas analysis showed significant hypoxemia with decreased PaO2. increased PaCO2. increased A-aDO2. Standard bicarbonate relative hypercapnia. Pulmonary function was unremarkable except for mild abnormalities in small airway function. Small airway function was demonstrated by the patient’s increased closed volume. Exertional expiratory mid-range flow is decreased.
2. Electrocardiogram
The electrocardiogram mainly shows right ventricular hypertrophy, rightward deviation of the electrical axis, extreme paraclockwise transposition, pulmonary P waves or spike-shaped P waves, complete or incomplete right bundle branch block, right ventricular hypertrophy with myocardial strain, etc. The electrocardiogram also shows right ventricular hypertrophy. Only a few patients had prolonged P-R and Q-T gaps and biventricular hypertrophy. Right ventricular hypertrophy is positively correlated with pulmonary hypertension.
3. Maximum mid-expiratory flow rate
Maximum mid-expiratory flow rate, clinically, sometimes it is easy to confuse hypercardiosis and pulmonary heart disease, the former is a chronic hypoxia caused by pulmonary vascular injury disease, while the latter is caused by chronic inflammation of the bronchial tubes and their surrounding tissues of the airway obstructive disease, so pulmonary function tests have an important value in the differentiation of the two. Patients with hypercardia have only mild small airway dysfunction, which is mainly manifested in the reduction of forceful expiratory mid-range flow (FEF25%～75%) and closed air volume (CV/VC%).
4. Echocardiography
Echocardiography, especially Doppler echocardiography, is the ideal non-invasive quantitative diagnosis of pulmonary hypertension.
5. X-ray examination
On X-ray examination, most patients have increased pulmonary hemorrhage and pulmonary stasis at the same time, and some cases have enlarged pulmonary hilar shadows and increased pulmonary texture. Cardiac changes are convex pulmonary artery segments, conical expansion, some even aneurysm-like convexity; right atrium and/or right ventricle enlargement, the heart is mitral valve type, the right lower pulmonary artery outer diameter widening. Individual patients may also have both right and left ventricles enlarged. X-ray diagnostic criteria for hypercardia: transverse diameter of the right lower pulmonary artery trunk > 17 mm, ratio of the transverse diameter of the right lower pulmonary artery trunk to the transverse internal diameter of the trachea > 1.10.
Diagnosis
Diagnosis can be made based on etiology, clinical manifestations and laboratory tests.
Differential diagnosis
The disease mainly affects the right heart function, with significant right ventricular hypertrophy and enlargement, and even failure, but sometimes it can also involve the left heart function at the same time. Therefore, in addition to differentiating from emphysema, pulmonary heart disease and coronary heart disease, coronary arteriosclerotic heart disease, rheumatic heart disease and viral cardiomyopathy, the disease should also be differentiated from other diseases.
Treatment
The most effective treatment is transfer to a lower altitude or plain area. Rest and low-flow oxygenation are important therapeutic measures for light patients who remain on the plateau, but heavy patients should be counseled to leave the hypoxic environment if they develop right heart failure. Clinical symptoms have been reported to improve significantly 3 to 4 months after transfer to a lower altitude, but symptoms may reappear and may worsen if the patient returns to the plateau after recovering on the plains.
Prognosis
Hemorrhagic cerebrovascular disease in chronic highland disease is relatively rare, but when it occurs, the symptoms are severe and the prognosis is poor.