Pulmonary Edema

The accumulation of fluid in the interstitial spaces.

Causes:

Increased hydrostatic pressure

Increased capillary permeability

Decreased plasma oncotic Pressure

Insufficient lymphatic drainage

Congestive Heart Failure and Edema

Failure of the fluid balance system due to heart's inability to pump blood volume.

Hydrostatic pressure increases may cause fluid filtration into the interstitial space that exceeds the lymphatic drainage, resulting in flooding of the interstitial spaces. Fluid will enter the alveoli if the interstitial fluid volume increases more than 100 ml - so even in mild pulmonary edema fluid can enter the alveoli - this causes the fine inspiratory crackles heard when listening to the chest. Increased fluid in the interstitial space between the capillary and alveolus, and fluid within the alveolus impair the diffusion of oxygen into the blood stream. As respiratory therapists, we can treat the symptom of the pulmonary edema by giving supplemental oxygen. The cause of the edema is treated by diet (decrease sodium intake - long story short - the kidneys misread what is going on and actually retain sodium), or improving cardiac funtion with medications. One of the quick ways to treat pulmonary edema is to give a diuretic such as Lasix and decrease the overall fluid volume.

Frequent causes:

Left ventricular failure - left side of the heart cannot properly eject blood and it builds up in the lungs

Mitral valve stenosis - narrowing of mitral valve between left atrium and left ventricle impedes blood return

Hypervolemia - too much IV fluid - called fluid overload.

Hydrostatic pressure increase is the only Cardiac related cause of pulmonary edema. (Also called CARDIOGENIC PULMONARY EDEMA)

Mechanisms of Pulmonary Edema

Factor

Value

Type

Clincal Problem

Hydrostatic Pressure

Increase

Cardiac

Left ventricular failure

Fluid overload

Mitral Stenosis

Capillary permeability

Increased

Noncardiac

Sepsis

Oxygen Toxicity

Acute Lung Injury

Oncotic Pressure

Decreased

Noncardiac

Protein starvation

Hemodilution

Renal loss of proteins

Lymphatic Drainage

Decreased

Noncardiac

Tumors

Pulmonary Interstitial Fibrosis

 

Increased capillary permeability is also called leaky capillary syndrome and referred to as noncardiogenic pulmonary edema. Usually have relatively normal heart function.