What Causes Pulmonary Edema
Pulmonary edema is the accumulation of fluid in the lung tissue. This situation can occur for multiple reasons. Pulmonary edema can be the consequence of various diseases. Heart failure is the most common cause in developed countries, followed by kidney disease.
Pulmonary edema is a serious illness characterized by difficulty in breathing, discomfort and coughing. Breathing is characterized by a sound that resembles the bubbling of water. The medical examination to determine severity of the edema consists of a radiograph of lung and a blood gas analysis. On the other hand, an additional diagnosis of the causes that accompany the edema is necessary. Treatment of pulmonary edema and prognosis will depend on the accompanying disease.
Pulmonary Edema Definition
Pulmonary edema is sudden (acute) or slow (chronic) accumulation of body fluid (serous fluid) in the lung tissue. The fluid initially accumulates between tissues of the lung. If process affects the air sacs (alveoli), it is alveolar pulmonary edema. Since gas exchange is dramatically reduced at this stage, pulmonary ventilation, circulation and such exchange are severely altered.
There are four stages of pulmonary edema:
- Stage I, interstitial pulmonary edema: Fluid is located only in the interstitial tissue.
- Stage II, alveolar pulmonary edema: Fluid is located in the air sacs (alveoli) and it is more advanced stage also in the bronchi.
- Stage III pulmonary edema: When there is a large amount of liquid, patients have a foamy sputum.
- Stage IV pulmonary edema: Cardiac arrest can occur due to the insufficient supply of oxygen in the body.
Pulmonary edema is a relatively common disease in developed countries because of the high prevalence of one of its causes (heart failure).
Pulmonary Edema Causes
Pulmonary edema is caused by an alteration in lung pressure. A balance between hydrostatic pressure and oncotic pressure is normally present in the lungs. The hydrostatic pressure ensures that blood flows through the capillaries and fluid flows through the blood vessels. On the other hand, oncotic pressure is given by the proteins in blood and ensures that the movement of the interstitial fluid is adequate. This will result in little fluid in the lung tissue.
Alterations caused by pulmonary edema usually occur when hydrostatic pressure increases or oncotic pressure decreases. The fluid can escape from capillaries and accumulate in the lung tissue or even in the alveoli. With an accumulation of more than two liters, lung can not perform its function properly and that is why, it will be limited.
Pulmonary edema can have different causes and it is distinguished between cardiogenic (due to heart disease) and non-cardiogenic edema, since cardiac problems are the main cause of pulmonary edema.
Cardiogenic Pulmonary Edema: Cardiogenic pulmonary edema is produced by a function of the heart. Heart can not pump enough blood into the body. This increases the pressure in the pulmonary veins or capillaries (hydrostatic pressure) from 8 mmHg to 25 mmHg. As a result, fluid from the blood vessels leave the interstices and alveoli.
This occurs when acute left ventricular failure occurs due to a heart attack, heart rhythm disturbances or inflammation of the heart muscle.
However, cause of cardiogenic pulmonary edema is also often chronic left ventricular insufficiency due to insufficient heart valve (valvular disease) or long-term stress caused by arterial hypertension.
Non Cardiogenic Pulmonary Edema: When there is pulmonary edema due to non-cardiogenic causes, other factors that come into play:
Lesions on the walls of the capillaries with the consequent increase of permeability with normal hydrostatic and oncotic pressure values. Possible causes are allergic reactions or gases of irritating action (chlorine or ammonia).
A decrease in oncotic pressure due to an absolute reduction of plasma proteins, either by malnutrition or by liver diseases.
A relative decrease of plasma proteins with reduction of oncotic pressure. It occurs in cases of increased fluid intake or decreased fluid excretion, as occurs in kidney diseases (pulmonary edema due to renal failure).
The one known as altitude sickness, which is produced by the difference between atmospheric pressure and body pressure.
Pulmonary Edema Symptoms
Pulmonary edema may cause different symptoms due to its stages. People who have pulmonary edema usullay feel discomfort, have difficulty breathing and restless breathing. People who have pulmonary often have coughs and may have a whitish and foamy substance. Pulse becomes very fast. As a result of the lack of oxygen cyanosis which consists of the blue coloration of the lips and areas(ears and tips of the fingers).
Pulmonary Edema Diagnosis
When pulmonary edema occurs, diagnosis can be made through a physical examination of patient. Significant signs of pulmonary edema are agitated breathing, rapid heart rate, cough and cyanosis.
Radiographs are especially useful for the diagnosis of interstitial pulmonary edema that are difficult to see. In addition, computed tomography (CT) may be useful in some cases, but it is usually not necessary.
If diagnosis of pulmonary edema is confirmed, causes of the disease should be sought. The electrocardiogram (ECG) may reveal cardiac arrhythmias or a heart attack. An ultrasound of the heart can show how heart works. With a blood gas analysis, doctor can find out the degree of oxygen deficiency. In addition, blood tests or tests of kidney function may be needed.
How To Treat Pulmonary Edema
When acute pulmonary edema occurs, intensive medical treatment is necessary. At all times keep your trunk erect and legs down. Breathing can be improved through the introduction of oxygen (O2) through nasal goggles. In advanced stages of the disease, positive pressure ventilation is sometimes necessary.
The pharmacological treatment is directed to the causes that produce the edema. When left ventricular heart failure is given, intravenous drugs that promote heart contraction and diuretics are given. If the cause of pulmonary edema is due to toxic products (edema from inhalation of toxic products), glucocorticoids will be used, either by inhalation or by intravenous application.
Continued treatment will depend on the cause of the disease. Chronic diseases such as heart or liver failure need to be treated properly. When pulmonary edema is due to renal disease which cause fluid accumulation, dialysis should be performed.