ARDS Three Times More Deadly Than Heart Attack

A critical lung condition called acute respiratory distress syndrome (ARDS) might not be familiar to you, but it probably should be. ARDS, a breathing failure that can occur in critically ill people with an underlying illness or injury, kills three times as many people as a heart attack, according to a study conducted at the University of Washington and reported in the New England Journal of Medicine late last year.

"ARDS is not a disease; it's a constellation of signs and symptoms. It affects both lungs and can be the result of direct lung injury or disease elsewhere in the body," says Randolph J. Lipchik, MD, Professor of Medicine at the Medical College of Wisconsin, Division of Pulmonary and Critical Care Medicine. "ARDS typically occurs in people who are being treated for another serious illness or those who have had major trauma or extensive burns to their body," he said.

ARDS is the most severe form of ALI (Acute Lung Injury) and is relatively common, with about 190,000 cases reported each year in the US alone. It can affect people of all ages. The number of deaths caused by acute lung injury in the US each year is about the same as deaths caused by breast cancer.

"ARDS first came to light during the Vietnam conflict when soldiers who were being resuscitated developed this syndrome," Dr. Lipchik said. At one time, about six out of ten people who developed ARDS died. Fortunately, today, with good care in a hospital intensive or critical care unit, that number has shrunk to about one in three, according to the National Institutes of Health.

Causes Unclear
What is behind this often deadly illness? "The cause of ARDS is not always well understood," Dr. Lipchik said. "It can occur in many situations, in persons with or without a lung disease. It is not clear why some patients develop ARDS and others do not."

To understand ARDS, it helps to understand how the lungs work. Air flows through tubes called bronchi into microscopic air sacs called alveoli. Very small blood vessels (capillaries) are imbedded in the walls of these air sacs. Oxygen passes through the thin walls of the alveoli into the bloodstream. Carbon dioxide, a waste product of cellular function throughout the body, passes from the bloodstream into the alveoli and then is exhaled.

"When alveoli are damaged by an injury or infection, some collapse and can allow abnormal influx of fluid, resulting in a severe limitation of the lung to take in oxygen. When the alveoli are flooded with fluid, it becomes difficult to breathe. The integrity of the lung tissue is lost," Dr. Lipchik said.

Signs and Symptoms
"Injury leading to ARDS can occur in two primary ways, direct lung injury such as breathing in vomited stomach contents, toxic inhalation, or severe pneumonia; and indirect lung injury such as major trauma or other critical illness such as bloodstream infection," Dr. Lipchik said.

The major signs and symptoms of ARDS are:

• rapid onset shortness of breath
• fast, labored breathing
• high blood pressure in the pulmonary arteries
• bluish skin color due to a low oxygen level in the blood

Diagnosis Sometimes Difficult
In the past, doctors were not always able to differentiate ARDS from other common illnesses. It can be confused with congestive heart failure, another common condition that can also cause acute respiratory distress. "In recent years, diagnosis has improved. We have come up with better, more standardized criteria. You can identify patients more easily," Dr. Lipchik said. Doctors often diagnose ARDS when:

• A person suffering from sepsis (severe infection) or injury develops breathing problems
• A chest x-ray shows fluid in the air sacs of both lungs
• Other conditions that could cause breathing problems have been ruled out

Treatment
Patients who develop ARDS are usually treated in the intensive or critical care unit of a hospital. The primary treatment consists of administering oxygen to increase its levels in the blood. "Treatment requires the use of mechanical ventilation," noted Dr. Lipchik. "Patients also must be treated for their underlying disease, whether it is an infection or other injury," he explained.

Treatment methods for ARDS have been improving as physicians learn more about the syndrome. "The way in which we administer mechanical ventilation is very important. If we overstretch the lungs, we can aggravate the lung injury instead of improving it," Dr. Lipchik said.

The University of Washington study regarding ARDS revealed some important information. "If we use smaller volumes of air to inflate the lung, it is beneficial to the patient's survival," according to Dr. Lipchik. "We use something called PEEP (Positive End-expiratory Pressure) to expand the parts of the lungs that can participate in exchanging oxygen for carbon dioxide."

Recovery Can Be Slow
Some individuals who survive ARDS heal quickly and recover completely in a relatively short time, but that is not always the case. "Many people who survive take six months to get back to normal. In fact, for many people, it may take a year for life to normalize for them, while some people never completely return to normal. Smokers who develop acute lung injury seem to do worse than non-smokers," Dr. Lipchik said, adding that mortality increases with the age of the patient.

ARDS is often associated with the failure of other organs and body systems. "Death usually is not caused by failure of the lungs; it is caused by the failure of other organs such as the liver and kidneys. Improved care in the ICU is important," Dr. Lipchik said.

Dr. Lipchik foresees a greater incidence of ARDS in the future. "As our population ages, we are likely to see an increase in ARDS," he said. Research continues as to why ARDS develops and how to prevent it.

JoAnn Petaschnick
HealthLink Contributing Writer

This article contains information from the US Department of Health and Human Services, National Institutes of Health.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.