Edema represents the accumulation of excess liquid in the
interstitial (extracellular) spaces of a tissue or in pre-existing cavities. It
may affect any organ, but most often it appears in : subcutaneous tissues, lung
and brain. There are two main types of pulmonary edema, hydrostatic and
noncardiogenic pulmonary edema. Each occur in different clinical conditions
require seperate therapy and have a different prognosis. There are many key
symptoms that can lead to the diagnosis of pulmonary edema and reasons why the
condition would arise. Following diagnosis comes the treatment and prognosis
will be discussed.
Many come to believe that the lungs are a dry
organ and the only time where fluid is involved is when the lungs develop a
condition called pulmonary edema. When in fact the lungs have a fluid that is
called filtrate that is in the interstitial spaces of the lungs. There are two
main types of pulmonary edema. The first is cardiogenic from left sided heart
failure. The second is is from injury. Both require different treatments and
the outcomes are also different.
Hydrostatic and osmotic pressure
Hydrostatic pressure is the pressure
experienced by a point inside the fluid. This is the pressure of nonflowing
water. Osmotic pressure is the pressure that stops the fluid transfer of the
semi permeable membrane in the lungs. The concentrated solute tends to move to
the less concentrated side. Often this means moving either in or out of a semi
permeable membrane when it comes to the lungs. Fluid in the lungs move through
the pulmonary capillary membrane. Raising the hydrostatic pressure could have
an effect on the body and the lungs. Common actions such as exercise do not
normally effect the permeability of the membrane by making it more permeable.
When the hydrostatic pressure does increase the membrane becomes more porous.
Edema is a buildup of fluid in the lungs that
can come from either an increase in pressure from fluid or from a weakening of
the membrane that normally regulates the amount of fluid that moves back and
forth through the pulmonary capillary membrane. When the left ventricle fails
the left side of the heart cannot adequately eject blood and it thus builds up
in the lungs. An elevation in pulmonary capillary wedge pressure results from
the hearts inability to pump the blood out of the pulmonary circulation. When
the fluid entered the lungs, this makes fine crackles when being auscultated. An
increase of fluid in the lungs makes diffusion impaired as it is difficult to
diffuse oxygen into the blood stream through all the fluid.
Pulmonary edema can also be caused by
neurogenic causes such as head trauma or seizures. Injury to the lungs direct
or indirect can also cause pulmonary edema. There is a decently large list of
things such as aspiration, severe infection, inhalation of hot or toxic gases.
The hanta virus and having a blood transfusion all can cause pulmonary edema. Obesity
and an infection such as a pneumonia can also be causes. Often noncardiogenic
edema can lead to ARDS. ARDS is acute respiratory distress syndrome.
Flash pulmonary edema.
pulmonary edema is a rapid onset of pulmonary edema. Often caused by an acute
myocardial infraction or mitral regurgitation. Mitral valve regurgitation is
when the valve is letting blood leak backwards into the heart. Typically,
valves work as one way gates the mitral specifically allowing the blood flow
from the left upper part of the heart, the atrium, to the lower, the ventricle.
Signs and symptoms.
Symptoms may start suddenly and gradually get
worse. With cardiogenic pulmonary edema symptoms tend to have a slower onset
than with noncardiogenic pulmonary edema. Cardiogenic pulmonary edema can be
associated with the signs of peripheral edema which can often be “pitting
edema”. You often also see JVD jugular vein distention with cardiogenic
pulmonary edema. Many patients with pulmonary edema tend to have tightening of
the chest with difficulty breathing and extreme shortness of breath. Patients
tend to have cyanosis which is characterized as a bluish tinting of the
nailbeds and the lips. Paleness and sweating is also a sign of pulmonary edema.
Signs that signify pulmonary edema can be fine crackles upon auscultation of
the chest. To verify such findings a physician may order a chest x-ray among
other test such s an electrocardiogram. Echocardiogram and on some occasions a
CT scan may be ordered to confirm pulmonary edema.
In efforts to raise the patients’ oxygen
levels oxygen is typically one of the first treatments ordered by the
physician. If simple oxygen is not enough to bring up the patients hypoxia a
noninvasive positive pressure ventilation also known as BIPAP can be used to
offer extra pressure to help push oxygen into the blood into the blood stream.
This extra pressure is needed due to the fluid in the lungs making it difficult
for oxygen to diffuse into the blood. In severe cases intubation is the chosen
method of oxygenation. Often diuretics are given in efforts to reduce the
amount of fluids the patient is retaining. Usually this means an increase of
urine output once the medication is given. Often cardiogenic pulmonary edema
patients also receive inotropic drugs which help the contractibility of the
heart to help sustain blood pressure. This can be given as a temporary
treatment while the underlying cause is addressed. Prevention can be for those
with underlying heart disease, control of those symptoms can help to prevent
pulmonary edema for heart patients.