Mixed chronic altitude sickness

Introduction to mixed chronic high altitude disease At present, the definition of mixed chronic high altitude disease has been basically consistent in China. It is a manifestation of high altitude hyperplasia of hypoxic red blood cells and high altitude heart disease caused by pulmonary hypertension. Mixed chronic high altitude sickness occurs mostly in plain settlers and a few natives who live in the plateau for a long time. The incidence of males is higher than that of females, and children are rare. According to reports, the prevalence of settlers in the Andean highlands of South America is significantly higher than that of the Himalayas, which may be related to the fact that the human body lived longer in the Himalayas than the Andean highlands. basic knowledge The proportion of illness: 0.002% Susceptible people: mostly occurred in plain settlers and a few inhabitants who lived in the plateau for a long time. Mode of infection: non-infectious Complications: pulmonary edema

The cause of mixed chronic high altitude disease

(1) Causes of the disease

Mixed chronic high altitude sickness occurs mostly in plain settlers and a few natives who live in the plateau for a long time. The incidence of males is higher than that of females, and children are rare. In addition, smoking, obesity and hypoventilation syndrome, and sleep-disordered breathing are also common. It is an important predisposing factor for the occurrence of hypoxemia in high altitude people.

(two) pathogenesis

Mixed chronic high altitude disease is characterized by excessive red blood cell hyperplasia, pulmonary hypertension and severe hypoxemia (Fig. 1), and alveolar hypoventilation caused by weakened respiratory drive is the basic factor in the development of this disease.

Compared with normal people at the same altitude, the red blood cell count, hematocrit and hemoglobin concentration of the disease were significantly increased, and various clinical symptoms appeared. Winslow performed bloodletting treatment on 8 patients with severe erythrocytosis, after 5 weeks of treatment. Hematocrit decreased from 75% to 45%, pulmonary arterial pressure decreased, cardiac output increased, and exercise capacity increased significantly, but the improvement of clinical symptoms has great individual differences. Due to excessive red blood cell hyperplasia, blood viscosity increases and blood flow is slow. Even microvascular thrombosis in small blood vessels, the ability to transport oxygen is weakened, and at the same time, due to the abnormal increase in the concentration of red blood cells 2,3-DPG, the hemoglobin oxygen dissociation curve shifts significantly to the right, and the blood oxygenation capacity in the lungs is weakened. Oxygen saturation is further reduced, and the cause of erythrocyte proliferation may be related to alveolar hypopnea caused by attenuated ventilation.

Significant pulmonary hypertension is another characteristic of this disease. Hultgren examined the hemodynamic changes of three chronic high altitude sickness, mixed chronic high altitude sickness in Peru (4540m), with an average pulmonary artery pressure of 50mmHg and a right atrial pressure of 9mmHg. 72%, normal lung function, when the patient inhaled 100% oxygen, the average pressure of the pulmonary artery dropped to 30mmHg, but still higher than the normal level of the same altitude, high altitude hypoxia is the root cause of pulmonary hypertension, long-lasting pulmonary hypertension Increases right heart load, right heart hypertrophy and failure; at the same time, hypoxic pulmonary vasoconstriction and pulmonary hypertension can cause morphological changes in the pulmonary arterioles, smoothing of smooth muscle in the middle layer of the blood vessels, resulting in stenosis, increased resistance to pulmonary circulation, and lack of The mechanisms of oxygen-induced pulmonary hypertension and morphological changes in pulmonary vessels are complex, including neurohumoral fluids, chemical mediators, and ion channels (see the section on hypertensive disease).

Ventilation/blood flow (V/Q) ratio abnormality and intrapulmonary shunt: A-aDO2 in patients with chronic high altitude disease is significantly larger than normal, which may be related to V/Q ratio imbalance. Under normal circumstances, alveolar ventilation and pulmonary blood flow distribution must be Uniform coordination, ie V/Q ratio of 0.8, mixed chronic high altitude disease, due to irregular contraction of hypoxic muscular pulmonary arterioles, uneven perfusion of blood flow, thickening of pulmonary vascular wall, narrowing or even complete occlusion of the lumen , and / or increased blood viscosity, intravascular thrombosis, etc., can lead to a large reduction in the total area of pulmonary capillaries, increased physiological void volume, in this case, alveolar ventilation is normal and pulmonary blood flow is reduced, The ratio of the two is increased, the gas in the lesion is not fully exchanged, and hypoxemia occurs. In addition, some patients cannot improve hypoxemia even if inhaled with high concentration of oxygen, which may be caused by significant pulmonary hypertension. Intrapulmonary movement. Caused by venous shunt.

Mixed chronic high altitude disease prevention

It is important to actively and effectively prevent and control respiratory infections.

Mixed chronic high altitude disease complications Complications pulmonary edema

Complicated with pulmonary infection, pulmonary edema, combined with right heart failure.

Mixed chronic high altitude sickness symptoms Common symptoms Tired loss of appetite, loss of appetite, erythrocytosis, dizziness, snoring, lethargy, edema, liver enlargement, right ventricular hypertrophy

Symptom

The disease is common in long-term living in the plateau above 3500m above sea level. Hultgren describes the clinical manifestations of a typical Monge disease: the patient is 43 years old, a British engineer who started a headache and dizziness after working in Morocco (4500m) in Peru for 1 year. Loss of appetite, fatigue, insomnia, work ability and efficiency are significantly reduced, physical examination blood pressure and heart rate are normal, cheeks and lips are severely cyanotic, pulmonary artery second tone hyperthyroidism and division; hematocrit 72%, white blood cell count is normal; ECG right ventricular hypertrophy, chest X-ray pulmonary artery segment protruded, right ventricle moderately enlarged; right heart catheterization, pulmonary systolic pressure 52mmHg, diastolic blood pressure 26mmHg, average pressure 40mmHg, right atrial pressure 7mmHg, his symptoms disappeared after leaving Peru, the pulmonary artery pressure returned to normal The most common symptoms of this disease are headache, dizziness, paresthesia, memory loss, sleep disorders including insomnia or lethargy, loss of appetite, decreased exercise tolerance.

2. Signs

Due to significant erythrocytosis and hypoxemia, the patient's face, lips, nose, ears, fingers (toes) are significantly blemishes, even dark red or black, individual may have clubbing, normal or low blood pressure, diastolic The pressure is increased slightly, the pulse pressure becomes smaller, and the heart rate is slightly increased, but generally it does not exceed 100 times/min. The right sternal edge apex beats, the ophthalmoscope sees arterial tortuosity, the vein dilates, the second sound of the pulmonary artery is hyperthyroidism or division, and the pulmonary artery The valvular area and / or apical area and the systolic murmur of the II-III level of the hair, the severe cases of oliguria, liver enlargement, facial and lower extremity edema.

Hybrid chronic altitude sickness examination

The number of red blood cells in the blood is abnormally increased, the concentration of hemoglobin in the blood is also abnormally increased, the total number of white blood cells and the classification are normal, and the platelets are the same as those in the same altitude. The main features of the myeloid granulocyte system are the hyperplasia of the red system and the possession of the red system. 33.3% of the cells, medium and young red blood cells were obvious, granulocyte and megakaryocyte system did not change significantly, pH was measured by pH value, blood gas analysis showed significant hypoxemia, PaO2 decreased, PaCO2 increased, A-aDO2 increased, standard bicarbonate relative hypercapnia, lung function in addition to mild airway function abnormalities, other no significant changes, small airway function in the patient's closed volume increased. Forced exhaled mid-flow decreased.

The electrocardiogram is characterized by right ventricular hypertrophy, right axis deviation, extreme clockwise transposition, pulmonary P wave or spike P wave, complete or incomplete right bundle branch block, right ventricular hypertrophy with myocardial strain Etc., only a small number of patients with PR and QT gap prolongation and double-chamber hypertrophy, right ventricular hypertrophy and pulmonary hypertension were positively correlated.

The maximum middle expiratory flow rate is sometimes confused with pulmonary heart disease. The former is a pulmonary vascular injury caused by chronic hypoxia, while the latter is an airway obstructive disease caused by chronic inflammation of the bronchus and its surrounding tissues. Therefore, pulmonary function tests have important value for the identification of the two. Patients with high heart disease have only mild small airway dysfunction, mainly in the forced exhalation mid-flow (FEF 25% to 75%), closed volume (CV/VC%), etc. reduce.

Echocardiography: In particular, Doppler echocardiography is the most ideal non-invasive method for the diagnosis of pulmonary hypertension. Echocardiography is mainly characterized by right ventricular outflow tract dilatation, right ventricular diameter, right ventricular outflow tract. The width of the left atrium did not change significantly, the ratio of the right ventricular outflow tract to the left atrium increased; the thickness of the right anterior wall also increased. The diagnostic criteria for high altitude heart disease developed by the Chinese Medical Association Plateau Medical Association is: right ventricular outflow tract > 33mm, right ventricular end diastolic diameter > 23mm.

X-ray examination: Most patients with pulmonary blood and pulmonary congestion can exist at the same time. In some cases, the lung portal enlarges, the lung texture increases, the heart changes to pulmonary artery segmentation, cone bulging, and some even aneurysm-like convex; right atrium and (or) the right ventricle is enlarged, the heart is mitral, the outer diameter of the right lower pulmonary artery is widened, and the left and right ventricles are also increased in individual patients. The diagnostic criteria for high-cardiac disease X-ray: the transverse diameter of the right lower pulmonary artery is >17 mm. The ratio of the transverse diameter of the right lower pulmonary artery to the transverse diameter of the trachea was >1.10.

Diagnosis and diagnosis of mixed chronic high altitude disease

Diagnostic criteria

1. Incidence above 3,500 m above sea level, can occur in plain settlers and a few plateaus living in the plateau for a long time. The clinical symptoms include headache, dizziness, fatigue, weakness, paresthesia, insomnia or lethargy, and cyanosis.

2. Hemoglobin > 200 g / L, hematocrit > 65% and red blood cell count > 6.5 × 1012 / L.

3. Significant pulmonary hypertension and extreme right ventricular hypertrophy, including echocardiography, right ventricular outflow tract > 33 mm, right ventricular end diastolic diameter > 23 mm; chest X-ray, right lower artery dry transverse diameter > 17 mm, right lung The ratio of the transverse diameter of the inferior artery to the transverse diameter of the trachea was >1.10; the right heart catheter was examined, and the mean pulmonary artery pressure was >25 mmHg.

4. Exclude other chronic cardiopulmonary diseases.

5. Turn to a low altitude area and the condition gradually improved.

Differential diagnosis

The disease mainly affects right heart function, and there is significant enlargement of right ventricular hypertrophy and even failure, but sometimes it can also affect left ventricular function. Therefore, in addition to identification with emphysema, pulmonary heart disease, congenital heart disease, etc., it should also be Coronary arteriosclerotic heart disease, rheumatic heart disease, and viral cardiomyopathy.

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