Pulmonary Edema Overview
Air enters the lungs through the mouth and nose, traveling through the trachea (windpipe) into the bronchial tubes. These tubes branch into progressively smaller segments until they reach blind sacs called alveoli. Here, air is separated from red blood cells in the capillary blood vessels by the microscopically thin walls of the alveolus and the equally thin wall of the blood vessels. The walls are so thin that oxygen molecules can leave air and transfer onto the hemoglobin molecule in the red blood cell, in exchange for a carbon dioxide molecule. This allows oxygen to be carried to the body to be used for aerobic metabolism and also allows the waste product, carbon dioxide, to be removed from the body.
If excess fluid enters the alveolus or if fluid builds up in the space between the alveolar wall and the capillary wall, the oxygen and carbon dioxide molecules have a greater distance to travel and may not be able to be transferred between the lung and bloodstream. This lack of oxygen in the bloodstream causes the primary symptom of pulmonary edema, which is shortness of breath.
Pulmonary Edema (cont.)
Pulmonary Edema Causes
Cardiogenic Pulmonary Edema
It may be helpful to understand how blood flows in the body to appreciate why fluid would "back up" into the lungs. The function of the right side of the heart is to receive blood from the body and pump it to the lungs where carbon dioxide is removed, and oxygen is deposited. This freshly oxygenated blood then returns to the left side of the heart which pumps it to the tissues in the body, and the cycle starts again.
Pulmonary edema is a common complication of atherosclerotic (coronary artery) disease. As the blood vessels that supply nutrients to the heart tissue progressively narrow, the heart muscle may not receive enough oxygen and nutrients to pump efficiently and adequately. This can limit the heart's ability to pump the blood it receives from the lungs to the rest of the body. If a heart attack occurs, portions of the heart muscle die and is replaced by scar tissue, further limiting the heart's pumping capability leaving it unable to meet its work requirements.
When the heart muscle is not able to pump effectively there is a back-up of blood returning from the lungs to the heart; this backup causes an increase in pressure within the blood vessels of the lung, resulting in excess fluid leaking from the blood vessels into lung tissue.
Examples of other conditions in which heart muscle may not function adequately include (this list is not all inclusive):
- cardiomyopathy (abnormally
functioning heart muscle);
- previous viral infection;
- thyroid problems,
and
- alcohol or drug abuse.
Another cause of pulmonary edema are mitral and aortic heart valve conditions. Normally, heart valves open and close at the appropriate time when the heart pumps, allowing blood to flow in the appropriate direction. In valvular insufficiency or regurgitation, blood leaks in the wrong direction. In stenosis of the heart valves, the valve becomes narrowed and doesn't allow enough blood to be pumped out of the heart chamber, causing pressure behind it. Failure of the mitral and aortic valves located in the left side of the heart can result in pulmonary edema.
Non-cardiogenic Pulmonary Edema
The following are some examples of causes of non-cardiogenic pulmonary edema.
- Kidney failure: In this
situation the kidneys do not remove excess fluid and waste products from the
body, and the excess fluid accumulates in the lungs.
- Inhaled toxins: Inhaled toxins (for example, ammonia or chlorine
gas, and smoke inhalation) can cause direct damage to lung
tissue.
- High altitude pulmonary
edema (HAPE): HAPE is a condition that occurs in people who
exercise at altitudes
above 8,000ft without having first acclimated to the high altitude. It commonly
affects recreational hikers and skiers, but it can also be observed in
well-conditioned athletes.
- Medication side effects: These may occur as
a complication of aspirin overdose or with the use of some
chemotherapy drug
treatments.
- Illicit drug use: Non-cardiogenic pulmonary edema is seen in patients who abuse illicit drugs,
especially cocaine and
heroin.
- Adult respiratory distress syndrome (ARDS):
ARDS is a major complication observed
in trauma victims, in patients with
sepsis, and
shock. As part of the body's attempt to respond to a crisis, the
antiinflammatory response attacks the lungs with white blood cells and other
chemicals of the inflammatory
response causing fluid to fill the air spaces of the lungs.
- Pneumonia: Bacterial or viral pneumonia infections are quite common; however, occasionally become complicated as a collection of fluid develops in the section of the lung that is infected.
Pulmonary Edema Symptoms
The shortness of breath may initially be manifested by difficulty doing activities that once were routine. There may be a gradual decrease in exercise tolerance, where it takes less activity to bring on symptoms. In addition to shortness of breath, some patients with pulmonary edema will also wheeze.
Orthopnea and paroxysmal nocturnal dyspnea are two variants of shortness of breath seen in association with pulmonary edema.
- Orthopnea describes shortness
of breath while lying flat. Some patients with orthopnea may use two or three
pillows to prop themselves up at night or resort to sleeping in a recliner.
- Symptoms of paroxysmal nocturnal dyspnea are generally described by the patient as wakening in the middle of the night, short of breath, with a need to walk around and perhaps stand by a window.
Pulmonary edema is due to left heart failure, in which pressure backs up into the blood vessels of the lungs, but some patients also have associated right heart failure. In right heart failure, the pressure backs up in the veins of the body, and fluid accumulation can occur in the feet, ankles, and legs as well as any other dependent areas like the sacrum, if the patient sits for prolonged periods of time.
Patients with high altitude pulmonary edema may also develop high altitude cerebral edema (inflammation and swelling of the brain). This may be associated with headache, vomiting, and poor decision making.
When to Seek Medical Care
Pulmonary edema can be a life-threatening situation. For persons in respiratory distress, emergency care should be sought immediately. In many places, 911 activates the emergency response system, and this may be appropriate if the patient is in distress. In addition to struggle with breathing, these individuals may be weak, lethargic, ashen or blue in color, pale,
and sweaty. They may be coughing up frothy sputum
Exams and Tests
Patient History
Past medical history may provide direction as to the cause. Patients at risk for cardiogenic pulmonary edema may have risk factors for heart disease, including high blood pressure, high cholesterol, diabetes, family history of heart disease, and smoking. Questions about signs of infection, medications and other complaints may be asked to access for reasons other than pulmonary edema that may be causing the shortness of breath.
Non-cardiogenic causes of pulmonary edema are also considered, especially in patients with no previous history of heart disease.
Physical Examination
Listening to the heart may reveal abnormal heart sounds or murmurs associated with valvular heart disease. If right heart failure exists, there may be swelling of the feet, ankles, and legs as well as jugular venous distention (a prominence of the veins in the neck associated with fluid overload).
Imaging and Other Tests
An electrocardiogram (EKG) may be helpful in diagnosing heart rhythm disturbances, previous heart attack, and ventricular hypertrophy (thickening of the heart ventricle muscle) associated with hypertension.
If there is concern about the structure and pumping capabilities of the heart, an echocardiogram may be considered. This uses ultrasound images which can help identify valve abnormalities, pumping efficiency of the heart, motion of the heart wall, and heart muscle thickness. The pericardium, the lining of the heart, can also be evaluated.
Blood Tests
Pulmonary Edema Treatment
Self-Care at Home
For high altitude pulmonary edema, the first treatment goal is to descend and bring the affected person to lower altitude if possible.
0 التعليقات:
إرسال تعليق