Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome
  
Definition/Description
 
Acute respiratory distress syndrome (ARDS) is breathing failure that can occur in critically ill persons with underlying illnesses. When one develops ARDS, severe fluid buildup occurs in both lungs and prevents the lungs from transfering oxygen from air into the body and carbon dioxide out of the body into the air. Noncardiogenic pulmonary edema; increased-permeability pulmonary edema; stiff lung; shock lung; and acute lung injury are its alternative names.
 
Causes
  
ARDS can be caused by any major swelling (inflammation) or injury to the lung. Some common causes include:
 
◆　Aspiration)
 
◆　Pneumonia
 
◆　Septic shock
 
◆　Trauma

ARDS leads to a buildup of fluid in the alveoli, which prevents enough oxygen from passing into the bloodstream.
 
The fluid buildup also makes the lungs heavy and stiff, and decreases the lungs' ability to expand. The level of oxygen in the blood can stay dangerously low, even if the person receives oxygen from mechanical ventilator through endotracheal tube.
 
ARDS often occurs along with the failure of other organ systems, such as the liver or the kidneys. Cigarette smoking and heavy alcohol use may be risk factors.
 
Symptoms/Signs

Symptoms usually develop within 24 to 48 hours of the initial injury or illness. Often, people with ARDS are so sick they are unable to complain of symptoms. However, the major signs and symptoms are:
 
◆ Dyspnea, tachypnea
 
◆ Hypotention and organ failure

◆ Cyanosis
 
Examinations/Tests
 
Listening to the chest with a stethoscope (auscultation) reveals abnormal breath sounds, such as crackles that suggest fluid in the lungs. Often the blood pressure is low. Cyanosis (blue skin, lips, and nails caused by lack of oxygen to the tissues) is often seen.

Tests used to diagnose ARDS include:

◆ Arterial blood gas

◆ Bronchoscopy

◆ CBC and blood chemistries

◆ Chest x-ray

◆ Sputum cultures and analysis

◆ Tests for possible infections

Occasionally an echocardiogram or Swan-Ganz catheterization may need to be done to rule out congestive heart failure, which can look similar to ARDS on a chest x-ray.

Treatment

Typically persons with ARDS need to be in an intensive care unit (ICU). The goal of treatment is to provide breathing support and treat the underlying cause of ARDS. This may involve medications to treat infections, reduce inflammation, and remove fluid from the lungs.

A breathing machine is used to deliver high doses of oxygen and a continuous level of pressure called PEEP (positive end-expiratory pressure) to the damaged lungs. Patients often need to be deeply sedated with medications when using this equipment.

Many different kinds of medicines are used to treat ARDS patients. Some kinds of medicines often used include:

◆ Antibiotics to fight infection

◆ Pain relievers

◆ Drugs to relieve anxiety and keep the patient calm

◆ Drugs to raise blood pressure or stimulate the heart

◆ Muscle relaxers to prevent movement and reduce the body's demand for oxygen

Complications

Common complications in ARDS patients are infections with hospital-acquired bacteria and leaks of air out of the lungs into other body spaces. These include:

◆ Lung damage (such as pneumothorax) due to use of high settings on the breathing machine needed to treat the disease

◆ Multiple organ system failure

◆ Pulmonary fibrosis

◆ Ventilator-associated pneumonia

Prognosis

About a third of people with ARDS die from the disease. Survivors usually get back normal lung function, but many people have permanent, usually mild, lung damage.

Many people who survive ARDS have memory loss or other problems with thinking after they recover. This is due to brain damage that occurred when the lungs weren't working properly and the brain wasn't getting enough oxygen.