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Pulmonary System

Critical Care

The Pulmonary System includes the lungs and the muscles of breathing, such as the diaphragm, which pump air into and out of the lungs. The purpose of the lungs is to get enough oxygen into the body and to get rid of carbon dioxide that is a waste product of the body.

Respiratory failure - Respiratory failure happens when a machine is needed to help with breathing.

Respiratory failure may happen if not enough oxygen is getting into the blood. The most common reasons for this are pneumonia (lung infection, see below), heart failure (called "pulmonary edema") and inflammation of the lungs (sometimes called ARDS that stands for "acute respiratory distress syndrome").

Respiratory failure may also happen if the lungs fail to get rid of carbon dioxide. You can think of the lung muscles, such as the diaphragms, as a pump that gets air into the body and carbon dioxide out of the body. If the lung muscles tire out, carbon dioxide can build up in the body and a breathing machine (see Information Sheet on Mechanical Ventilators) may be needed to get rid of it while the muscles rest. Some common reasons for this type of failure include asthma and other obstructive lung diseases such as emphysema.

Breathing machines don't fix the reasons for respiratory failure and there are many risks of staying on a machine. Doctors and hospital staff try to understand the reasons for respiratory failure, treat the causes as fast as possible and then try to get the patient off the breathing machine. This is reviewed in the Information Sheet on Weaning from Mechanical Ventilation.

Pneumonia - is an infection of the lungs and a very common cause of critical illness. It happens when a germ, such as a bacteria or virus, enters the body, usually through the nose or mouth, and then goes down into the lungs causing them to flood with pus and fluid. Pneumonia can be a problem that leads to the need for hospitalization or it can occur as a complication in the hospital. Pneumonia often causes fever, cough and shortness of breath. Most pneumonias can be treated with drugs called antibiotics. Some pneumonias can be so serious that they stop enough oxygen from getting into the body, and the patient must be admitted to the hospital. If the pneumonia is very serious, a machine may be needed to help the patient to breathe until antibiotics and the patient's body fight off the infection (see Information Sheet on Mechanical Ventilators).

When a patient has respiratory failure (see explanation above) and has a tube in the lungs connected to a breathing machine, there is a risk of germs entering the lungs through the tube. These types of pneumonias can make patients very sick because the germs in the hospital are often more difficult to treat than those outside the hospital (see section on Multiple Drug Resistant infections).

Pulmonary embolus - Many patients who are admitted to the hospital don't get up and walk around every day because they are so sick. As a result of staying in bed, sometimes blood clots can form in the legs and pieces can break off and move to the lungs where they cause shortness of breath and chest pains. This is called pulmonary embolus. Very serious pulmonary embolus can cause respiratory failure (see explanation above) or even death. Blood thinners (medicines like heparin and coumadin) are used to treat pulmonary embolus and may be used to prevent blood clots of patients who are at risk.