Pulmonary edema is a medical emergency and
requires immediate care. Although it can sometimes
prove fatal, the outlook is often good when you
receive prompt treatment along with therapy for the
underlying problem.
Your lungs contain millions of small, elastic air
sacs called alveoli. With each breath, these air
sacs take in oxygen and release carbon dioxide, a
waste product of
metabolism. Normally, the exchange
of oxygen and carbon dioxide takes place without
problems. But sometimes increased pressure in the
blood vessels in your lungs forces fluid into the
air sacs, filling your lungs with fluid and
preventing them from absorbing oxygen - a condition
called pulmonary edema.
In most cases, heart problems are the cause of
pulmonary edema. But fluid can accumulate in your
lungs for other reasons, including lung problems
such as pneumonia, exposure to certain toxins and
medications, and climbing or living at high
altitudes.
Signs and symptoms
Depending on the cause, the signs and symptoms of pulmonary edema may
appear suddenly or develop slowly over weeks or months. Signs and
symptoms that develop over time may include:
-
Difficulty
breathing when you're lying flat as opposed to sitting up.
-
Awakening
at night with a breathless feeling.
-
Having more
shortness of breath than normal when you're physically active.
-
Significant weight
gain when pulmonary edema develops as a result of congestive heart
failure, a condition in which your heart pumps too little blood to
meet your body's needs. This causes fluid to accumulate in your
tissues.
Signs and symptoms that come on suddenly are usually severe and may
include:
-
Extreme
shortness of breath or difficulty breathing
-
A feeling of
suffocating or drowning
-
Wheezing
or grunting sounds when breathing
-
Anxiety and
restlessness
-
A cough that
produces frothy, pink sputum
-
Excessive sweating
-
Pale skin
If you develop any of these signs or symptoms, call for emergency
medical assistance right away. Pulmonary edema can be fatal if not
treated.
Causes
Your lungs are two spongy organs surrounded by a moist membrane (the
pleura). Stretched out, they would cover about 100 square yards the
size of a badminton court. Although your lungs can hold up to 4 quarts
of air, you generally inhale only about a pint of air with each breath.
Two major airways (bronchi) carry air into your lungs. These airways
subdivide into smaller airways (bronchioles) that finally end in
clusters of tiny air sacs. Your lungs have about 300 million of these
air sac clusters, which inflate like miniature balloons every time you
inhale.
Wrapped around each air sac are tiny capillaries that connect the
arteries and veins in your lungs. The capillaries are so narrow that red
blood cells have to pass through them in single file. Each red blood
cell absorbs oxygen, while the plasma the fluid containing the red
blood cells releases carbon dioxide.
But in certain circumstances the alveoli fill with fluid instead of air,
preventing oxygen from being absorbed into your bloodstream. A number of
factors can cause fluid to accumulate in your lungs, but most have to do
with your heart (cardiac pulmonary edema). Understanding the
relationship between your heart and lungs can help explain why.
How your heart works
Your
heart is composed of two upper and two lower chambers. The upper
chambers (the right and left atria) receive incoming blood. The lower
chambers, the more muscular right and left ventricles, pump blood out of
your heart. The heart valves which keep blood flowing in the right
direction are gates at the chamber openings.
Normally, deoxygenated blood from your body enters the right atrium and
flows into the right ventricle, where it's pumped through large blood
vessels (pulmonary arteries) to your lungs. There, the blood releases
carbon dioxide and picks up oxygen. The oxygen-rich blood then returns
to the left atrium, flows through the mitral valve into the left
ventricle, and finally leaves your heart through another large artery,
the aorta. The aortic valve at the base of the aorta keeps the blood
from flowing backward into your heart. From the aorta, the blood travels
to the rest of your body.
Cardiac pulmonary edema also known as congestive heart failure
occurs when the left ventricle isn't able to pump out enough of the
blood it receives from your lungs. As a result, pressure increases
inside the left atrium and then in the pulmonary veins and capillaries,
causing fluid to be pushed through the capillary walls into the air
sacs.
Several medical conditions can cause the left ventricle to become weak
or to fail, including:
-
Coronary artery
disease.
Over time, the arteries that supply blood to your heart (coronary
arteries) can become narrow from fatty deposits (plaques). A heart
attack occurs when a blood clot forms in one of these narrowed
arteries, blocking blood flow and damaging the portion of your heart
muscle supplied by that artery. The result is that the damaged heart
muscle can no longer pump as well as it should. Although the rest of
the heart tries to compensate for this loss, it's either unable to
do so effectively or it's weakened by the extra workload. When the
pumping action of the heart suddenly weakens, fluid backs up into
your lungs.
-
Cardiomyopathy.
When your heart muscle is damaged by causes other than blood flow
problems, the condition is called cardiomyopathy. Often,
cardiomyopathy has no known cause, although it sometimes runs in
families. Less common causes include infections (myocarditis),
alcohol abuse and the toxic effects of drugs such as cocaine and
some types of chemotherapy. Because cardiomyopathy weakens the left
ventricle your heart's main pump it may not be able to respond
to conditions that require it to work harder, such as a surge in
blood pressure or infections. When the left ventricle can't keep up
with the demands placed on it, fluid backs up into your lungs.
-
Heart
valve problems (mitral or aortic heart valve disease).
In mitral or aortic valve disease, the valves that regulate blood
flow either don't open wide enough (stenosis) or don't close
completely(aortic or mitral valve insufficiency). This allows blood
to flow backward through the valve. When the valves are narrowed,
blood can't flow freely into your heart and pressure in the left
ventricle builds up, causing the left ventricle to work harder and
harder with each contraction. The increased pressure extends into
the left atrium and then the pulmonary veins, causing fluid to
accumulate in your lungs. On the other hand, if the mitral valve
leaks, some blood is backwashed toward your lung each time your
heart pumps. If the leakage develops suddenly because of the
snapping of the valve cord, you may develop sudden and severe
pulmonary edema.
-
High blood
pressure (hypertension).
Untreated or uncontrolled high blood pressure causes a thickening of
the left ventricular muscle, and accelerates coronary artery
disease.
If pulmonary edema persists, it can raise pressure in the pulmonary
artery and eventually the right ventricle begins to fail. The right
ventricle has a much thinner wall of muscle than does the left side. The
increased pressure backs up into the right atrium and then into various
parts of the body, where it can cause leg swelling (edema), abdominal
swelling (ascites) or a buildup of fluid in the pleural space (pleural
effusion).
Noncardiac pulmonary edema
Not
all pulmonary edema is the result of heart disease. Fluid may also leak
from the capillaries in your lungs' air sacs because the capillaries
themselves become more permeable or leaky, even without the buildup of
back pressure from your heart. In that case, the condition is known as
noncardiac pulmonary edema because your heart isn't the cause of the
problem. Some factors that can cause increased capillary permeability
leading to noncardiac pulmonary edema are:
-
Lung
infections.
When pulmonary edema results from lung infections,
such as pneumonia, the edema occurs only in the part of your lung
that's inflamed.
-
Exposure to
certain toxins.
These include
toxins you inhale such as chlorine, ammonia or nitrogen dioxide
as well as those that may circulate within your body. For example,
women giving birth may develop pulmonary edema when amniotic fluid
reaches the lungs through the veins of the uterus (amniotic fluid
embolism).
-
Severe allergic
reactions (anaphylaxis).
You can have
serious allergic reactions to some medications as well as to certain
foods and insect venom.
-
Smoke
inhalation.
Children and older adults are especially vulnerable
to lung damage caused by breathing harmful vapors and gases in smoke
from structural fires. The smoke from these fires often contains
chemicals that irritate the lining of the lungs, causing the tiny
blood vessels to leak.
-
Near-drowning
and drowning.
-
Drug overdose.
Drugs ranging from narcotics, such as heroin, to aspirin can cause
noncardiac pulmonary edema. Aspirin-induced pulmonary edema can
occur in people who take increasingly large doses of aspirin to
relieve pain or other symptoms. For reasons that aren't clear,
smokers who use aspirin are at greater risk.
-
Acute
respiratory distress syndrome (ARDS).
This serious
disorder, which affects hundreds of thousands of people every year,
occurs when your lungs suddenly become unable to take in enough
oxygen. More than 30 conditions can cause ARDS, including severe
injuries (trauma), systemic infection (sepsis), pneumonia or shock.
ARDS sometimes also develops after extensive surgery. Symptoms
usually appear within 24 to 72 hours after the original illness or
trauma.
-
High altitudes.
Mountain climbers and people who live in or travel to high-altitude
locations run the risk of developing high-altitude pulmonary edema (HAPE).
This condition which typically occurs at elevations above 8,000
feet can also affect skiers who start exercising at higher
altitudes without first becoming acclimated. But even people who
have hiked or skied at high altitudes in the past aren't immune.
Although the exact mechanism isn't completely understood, HAPE seems
to develop as a result of increased pressure from constriction of
the pulmonary capillaries. Symptoms include headaches, insomnia,
fluid retention, cough and shortness of breath. Without appropriate
care, HAPE can be fatal.
When to seek medical advice
Pulmonary edema is life-threatening. Get emergency assistance if you
have any of the following acute signs and symptoms:
-
Trouble breathing
or a feeling of suffocating (dyspnea)
-
A bubbly, wheezing
or grunting sound when you breathe
-
Pink, frothy
sputum when you cough
-
Profuse sweating
-
Light-headedness
-
A blue or gray
tone to your skin
-
A severe drop in
blood pressure
Acute pulmonary edema is likely to be incapacitating, so don't attempt
to drive yourself to the hospital. Instead, dial emergency
medical care and wait for help.
Pulmonary edema
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