Overview
The human body is unable to adapt quickly to the low pressure and low oxygen environment in the plateau area and the disease is caused.
Symptoms include difficulty in breathing, coughing, coughing up white or frothy sputum, rapid heartbeat, dizziness and headache.
Bed rest, oxygen therapy, lowering the altitude, combined with medication.
Untimely treatment can lead to death, but most of them can be cured with timely treatment.
Definition
Altitude sickness refers to a group of diseases characterized by hypoxia that occur in people who move from the plains to the plateau and stay there for a short period of time due to insufficient adaptation to the plateau environment.
Highland disease can be divided into acute highland disease, chronic highland disease, the former can be divided into three types, which can cross each other or co-exist with each other, including acute highland reaction, highland pulmonary edema, highland cerebral edema.
High-altitude pulmonary edema (HAPE) is a serious plateau disease with an acute onset, rapid development and fatal outcome, which develops from acute altitude reaction, and is a non-cardiogenic pulmonary edema, which usually develops within 1-3 days of rapid entry into a plateau area (often above 3000 meters above sea level) [ 1,2 ].
Plateau pulmonary edema begins with an acute plateau reaction, followed by typical symptoms such as tachycardia, dyspnea, worsening of dry cough, and coughing up pink foamy sputum.
The faster the altitude gain and the higher the altitude reached, the more common the onset and the more severe the symptoms.
Morbidity
The incidence of high altitude pulmonary edema (HAPE) has been shown to range from 0.6% to 6% at an altitude of 4,500 meters, and from 2% to 15% at an altitude of 5,500 meters.
Patients with a previous history of HAPE have a recurrence rate of up to 60% [ 1 ].
Etiology.
The underlying cause of highland pulmonary edema is acute hypoxia, and the pathogenesis is complex.
Pathogenesis.
Anyone who travels to a plateau may develop the disease because of the inability to adapt quickly to the low-pressure, low-oxygen environment [ 3 ]. Excessive salt intake, rapid climbing, overexertion, cold, respiratory infections, use of sleeping pills, and a past history of highland pulmonary edema are more likely to develop the disease.
Pathogenesis
The pathogenesis of plateau pulmonary edema is complex.
Due to the reduction of atmospheric pressure and partial pressure of oxygen in the plateau region, hypoxia occurs after entering the plateau region from the plains. In order to adapt to the low oxygen environment, the body needs adaptive changes. However, the adaptive ability of human to plateau hypoxia is limited, and hypoxia easily occurs when the altitude is too high and the elevation is too fast.
Acute hypoxia to pulmonary small artery spasm, sustained small artery spasm leads to increased pulmonary circulation resistance, pulmonary capillary pressure significantly increased, vascular wall permeability increased, plasma exudate increased, the occurrence of pulmonary hypertension, causing plateau pulmonary edema.
Due to the obstacle of coagulation and fibrinolytic mechanism, micro thrombus is formed in small pulmonary arteries and capillaries, thus the blood flow is blocked, resulting in the transfer of all the blood of the lungs to the unobstructed area, resulting in a sudden increase in the blood flow and pressure of the local capillaries, and the water leaks out to the interstitium and alveoli.
In addition, acute hypoxia can cause alveolar wall and pulmonary capillary damage, reduction of alveolar surface active substances, release of vasoactive substances, aggravation of pulmonary capillary endothelial damage and leakage, and contribute to the aggravation of pulmonary edema [ 4-7 ].
Symptoms.
When patients enter plateau area, they first have acute plateau reaction manifestation, and typical plateau pulmonary edema symptoms mostly appear within 1~3 days, and a small number of people can develop after 10 days [ 4-5 ].
Acute plateau reaction
Dizziness, double frontal pain, transient or slightly accelerated heartbeat, chest tightness, shortness of breath, anorexia, nausea, vomiting, fatigue and other symptoms may occur. Some people develop bruising of the lips and nails.
Mild cases usually resolve after 24 to 48 hours on the plateau and disappear after a few days.
A few may develop plateau pulmonary edema and/or plateau cerebral edema.
Typical Symptoms
Main Symptoms
Dyspnea
From the early stage of chest tightness and shortness of breath, gradually aggravated to the emergence of dyspnea, which is more obvious after climbing slopes and fast walking.
As the condition worsens, dyspnea at rest gradually develops. The patient often needs to sit on the edge of the bed or on a chair to alleviate the dyspnea.
Cough
Early on, it may be a mild dry cough, mostly when climbing or walking fast; when the condition worsens, dry cough may also appear when resting.
It is often mistaken for a cough caused by an upper respiratory tract infection due to climate change in the highlands.
As the disease progresses, white sputum is coughed up, and in severe cases, pink frothy bloody sputum is coughed up.
Rapid heartbeat
In the later stages of the disease, severe hypoxemia may occur, causing compensatory tachycardia, which is characterized by a persistent rapid heartbeat, which may be accompanied by a significant increase in the heart rate, or even by a sense of panic.
Other symptoms
Some patients may develop low-grade fever, with body temperature usually not exceeding 38°C.
Exacerbation of symptoms such as fatigue, headache and dizziness may occur, and in severe cases, unresponsiveness, drowsiness, or even coma may occur.
Complications
Acute mountain sickness
Also known as acute altitude sickness.
The proportion of patients with acute mountain sickness combined with plateau pulmonary edema can be as high as 50% [1].
Patients mainly present with headache, fatigue, loss of appetite, nausea or vomiting symptoms [8].
It usually resolves after 24-48 hours of stay at the plateau.
Plateau cerebral edema
Also known as neurogenic altitude sickness.
About 14% of patients with plateau pulmonary edema can be complicated by plateau cerebral edema [1].
Patients mainly present with severe headache, persistent vomiting, difficulty in movement, rigidity, drowsiness, impaired consciousness and even coma, which can be life-threatening in severe cases [9].
Seek medical attention
It is recommended to consult a doctor when acute altitude sickness occurs in the early stage, instead of waiting for the typical symptoms of altitude pulmonary edema to appear.
Department of Medicine
Respiratory medicine
When dizziness, headache, chest tightness and other suspected acute plateau reactions occur at higher altitudes, it is recommended to seek prompt medical attention from the Department of Respiratory Medicine.
Emergency Department
If symptoms such as severe dizziness or headache, difficulty in breathing, or unconsciousness occur, it is recommended that you be sent to the Emergency Department in time or call the 120 emergency number.
Preparation for medical treatment
Preparing for medical treatment: registration, preparation of documents, common problems
Tips for medical treatment
It is recommended to wear loose-fitting clothes and avoid wearing clothes made of metal to facilitate medical checkups or examinations.
Patients who are pregnant or preparing for pregnancy should inform the doctor in time.
Preparation Checklist
Symptom Checklist
Pay special attention to the time of onset of symptoms, special manifestations, etc.
What are the discomforts now? What are the most serious symptoms?
Is there dizziness, headache, chest tightness, panic, dyspnea, is it worse when lying down, is there any edema in both lower extremities? Is there a significant correlation with elevation?
Is there a cough? How long has the cough been present? What makes it worse or relieves it?
Is there sputum? What does the sputum look like?
Are there any other discomforts such as fever, malaise, nausea, loss of appetite?
Medical History Checklist
Has there been a recent trip from a low altitude area to a high altitude area? Has a similar condition occurred on previous trips to high altitude areas?
Any previous physical discomfort while at low altitude?
Any previous chronic respiratory disease such as COPD, bronchial asthma?
Any chronic cardiovascular disease, such as heart failure, hypertension?
Any recent exposure to cold?
Checklist
Test results in the last 1 week, which can be brought to the doctor’s appointment
Laboratory tests: blood test, troponin, brain natriuretic peptide, coagulation function.
Imaging tests: chest X-ray, chest CT, chest ultrasound, echocardiography.
Electrocardiogram.
Medication list
Medication used in the last 1 week, if available in a box or package, bring with you to the doctor’s office
Calcium channel blockers: e.g. nifedipine, amlodipine, etc.
Glucocorticoid: e.g. dexamethasone, hydrocortisone, etc.
Diuretics: e.g. hydrochlorothiazide, spironolactone tablets, furosemide, etc.
Diagnosis
In the process of diagnosis of altitude sickness, it is necessary to ask the medical history, observe the signs and symptoms, and carry out some necessary medical examinations, as well as pay attention to the differentiation.
Diagnostic basis
Medical history
The patient has recently (mostly within 10 days) arrived at a high altitude (mostly over 3000 meters) from a low altitude.
Clinical manifestations
Symptoms
Coughing, dyspnea, dizziness, headache, rapid heartbeat.
Physical signs
Auscultation reveals widespread wet rales in the lungs bilaterally, often accompanied by sputum sounds, which are often masked by rales.
The heart rate is markedly increased, and some patients have a grade I-III wind-blowing systolic murmur in the tricuspid valve area and pulmonary valve auscultation area.
The lips, earlobes, face, tongue, and nails appeared to varying degrees of bruising.
Very few severe patients have jugular venous rage, hepatomegaly and bilateral lower extremity edema.
Laboratory Tests
Blood count
Mild leukocytosis may be present.
If the disease persists for a long period of time, it may result in a red blood cell count of more than 7.0 x 1012/L, a hemoglobin concentration of more than 180 g/L, and a hematocrit of more than 60%.
Troponin
It is mainly used to determine whether hypoxia has resulted in myocardial damage due to ischemia and hypoxia.
Patients who present with myocardial damage may have elevated serum troponin.
Brain Natriuretic Peptide
Used primarily to assist in the assessment of cardiac function.
Patients may have elevated serum brain natriuretic peptide (BNP) levels and brain natriuretic peptide precursor (pro-BNP), suggesting cardiac insufficiency.
Chest Imaging
Chest X-ray
Chest X-ray is the most commonly used screening tool.
Chest radiographs of patients with high plateau pulmonary edema show diffuse patchy or cloudy shadows in the lung fields bilaterally, as well as punctate or nodular shadows.
The most obvious areas of shadow distribution are adjacent to the lung hilums, which are fan-shaped and have the shape of “bat wings” or “butterfly”, while the lung apices and lung bases are seldom involved.
In mild cases or early stages of the disease, there may only be thickening of the lung texture, while in severe cases, it may be accompanied by pleural effusion.
Chest CT
Chest CT examination can more clearly show the patchy lobular glassy and solid shadows in the lungs, which is mainly used to identify with other diseases, and is not a routine examination.
Chest ultrasound
Chest ultrasound is commonly used to identify highland pulmonary edema in remote areas where chest imaging is not available.
Chest ultrasound shows a “comet’s tail sign” (a fan-shaped spread from the surface of the lungs), which confirms the diagnosis of highland pulmonary edema.
Electrocardiogram
An electrocardiogram (ECG) is a mandatory test for highland pulmonary edema to assess heart rate and myocardial ischemia and hypoxia.
Patients may have a variety of ECG changes, including sinus tachycardia, rightward deviation of the electrical axis, right bundle branch block, pulmonary P-wave or P-wave cusp, inverted T-wave, and decreased S-T segment.
As the clinical symptoms improve or recover, the ECG returns to normal.
Echocardiography
Echocardiography can be used to determine the patient’s cardiac function, the presence or absence of increased pulmonary artery pressure and abnormal septal motion.
Diagnostic Criteria
A diagnosis of altitude sickness can be made if the following conditions are also met
Onset after entering a higher altitude or plateau area.
Presence of typical symptoms as described in the preceding paragraphs, with symptoms clearly associated with altitude, speed of climbing, and failure to undergo an acclimatization period.
Except for related illnesses that resemble the manifestations of altitude sickness.
Oxygen therapy or euthanasia is clearly effective.
Differential diagnosis
It should be differentiated from pneumonia, plateau bronchitis, pulmonary embolism, pulmonary infarction, pneumothorax, and other causes of pulmonary edema (e.g., pharmacologic or neurogenic pulmonary edema), only two of which are listed below.
Lung infections
Similarities
Both patients may present with clinical manifestations such as cough, sputum, dyspnea, and fever.
Examination may reveal hypoxemia, with increased white blood cell counts seen on routine blood tests, and patchy lung images seen on chest imaging.
Differences
Patients with pneumonia may present with high fever (temperature >39°C), often accompanied by coughing up yellow sputum.
Patients with pneumonia have a more pronounced elevated white blood cell count, and inflammatory markers such as calcitoninogen and C-reactive protein may be significantly elevated.
Evidence of pathogenesis is present, such as positive sputum cultures and nucleic acid tests.
Empiric antibiotic therapy is often effective.
Pulmonary embolism
Similarities
Both may present with chest pain, rapid heart rate, and dyspnea.
Differences
Patients with pulmonary embolism often have severe chest pain.
Serum D-dimer is significantly elevated.
Chest X-ray has no obvious lung patchy shadow, only a small number of patients with pulmonary infarction can be seen wedge-shaped lesions.
CT of the pulmonary artery suggests a localized filling defect in the diseased pulmonary artery. Venous ultrasound of both lower extremities often suggests thrombosis.
Treatment
Aim of treatment: improve symptoms, eliminate pulmonary edema, prevent complications and reduce mortality.
Treatment principles: early recognition, early treatment, absolute bed rest, active oxygen therapy, reducing altitude, combined drug therapy to reduce pulmonary artery pressure and improve pulmonary edema [4-5,9-10].
General treatment
Rest and warmth
Absolute bed rest, adopt semi-sitting position or high pillow position.
Pay attention to keep warm and avoid getting cold.
Oxygen therapy
Oxygen therapy is the first line of treatment for highland pulmonary edema. All patients should be given oxygen, often through a mask.
For severe hypoxia, high-flow continuous oxygen (10 liters/minute) can be given, usually for no more than 24 hours, and then changed to low-flow continuous oxygen (2-4 liters/minute) to avoid oxygen toxicity [5].
For those who are hiking or trekking at high altitude, the portable hyperbaric oxygen chamber with light weight is more convenient than conventional compressed oxygen cylinder. It can effectively relieve the condition.
Transfer to lower altitude
Reducing altitude is not a necessary measure for treatment.
However, in remote areas where oxygen therapy is not available, it is recommended that once highland pulmonary edema is suspected, a rapid transfer to an area below 3,000 meters above sea level where oxygen therapy is available is recommended.
If oxygen therapy is not effective, immediate transfer to a lower altitude is also recommended.
Medication
Nifedipine
In patients who cannot be transported in time, sublingual or oral nifedipine can reduce pulmonary artery pressure and improve oxygenation, thus reducing symptoms.
Aminophylline injection
Administered by slow, uniform intravenous injection.
Aminophylline is bronchospasmolytic, cardiotonic, diuretic, and significantly reduces pulmonary artery pressure.
Glucocorticoids
Commonly used drugs include hydrocortisone and dexamethasone.
They are administered by intravenous drip and the duration of treatment should be controlled.
Diuretics
Hydrochlorothiazide or spironolactone tablets can be given orally in mild cases, and furosemide injection is mostly used intravenously in severe cases.
It can reduce blood volume, reduce cardiac load and improve cardiac function.
Other drugs
In the presence of rapid atrial fibrillation, digitalis and antiplatelet drugs (aspirin, dipyridamole, ticlopidine or cilostazol) are applied.
Prognosis
The prognosis is not identical in different patients and is influenced by a number of factors.
Cure
Highland pulmonary edema is acute, severe, and has a high mortality rate. It has been shown that up to 50% of patients with highland pulmonary edema die without active treatment. If actively treated, the mortality rate can be reduced to about 14% [1].
Prognostic factors
The prognosis of plateau pulmonary edema is influenced by a number of factors, and the following factors can help to improve the prognosis, of which early recognition and early treatment are critical.
Early recognition and treatment.
Less severe disease.
Excellent hospital care.
Experienced doctors.
The patient’s cooperation with treatment is good.
Daily
Daily Management
Dietary management
Light and easy-to-digest diet, avoiding foods such as fatty meat, bacon, fried food, chocolate, etc., which may aggravate the symptoms of nausea and vomiting.
Life management
Absolute bed rest, avoid exercise for the time being.
Avoid catching cold.
Maintain a stable mood, avoid anger and impatience.
Disease monitoring
By looking in the mirror, observe whether the bruising of the mouth and lips improves, and directly observe whether the color of the nails gradually returns to red.
Self-observe whether symptoms such as dizziness, headache and dyspnea improve.
Pay attention to changes in blood oxygen saturation.
Prevention
Prevention of highland pulmonary edema is essential. The following measures can help reduce the risk of the disease.
Before entering the plateau, you must undergo a rigorous health examination, and should not enter the plateau if you suffer from serious cardiovascular or respiratory diseases.
Take high altitude illness seriously, but do not be overly fearful of it.
Know the altitude of your destination in advance and control the speed of entering the plateau. If there is enough time, it is recommended not to exceed 300 meters/day.
Within one week of entering the plateau, avoid strenuous exercise and gradually increase the amount of activity.
Take sufficient rest and avoid fatigue.
Keep warm and avoid cold.
Carry a portable oxygen cylinder.
If there is a history of plateau pulmonary edema in the past, the possibility of reoccurrence is high, preventive medication can be used, and the drugs of choice are dexamethasone, acetazolamide, nifedipine and so on.
Once acute plateau reaction occurs, treat it promptly to avoid aggravation to plateau pulmonary edema.