Acute Respiratory Distress Syndrome (ARDS)

Any disease or condition that injures the lungs can cause ARDS. More than half of the people with ARDS develop it as a consequence of a severe, widespread infection (sepsis Sepsis and Septic Shock Sepsis is a serious bodywide response to bacteremia or another infection plus malfunction or failure of an essential system in the body. Septic shock is life-threatening low blood pressure ... read more ) or pneumonia Overview of Pneumonia Pneumonia is an infection of the small air sacs of the lungs (alveoli) and the tissues around them. Pneumonia is one of the most common causes of death worldwide. Often, pneumonia is the final... read more . Some other causes include

When the small air sacs (alveoli) and tiny blood vessels (capillaries) of the lungs are injured, blood and fluid leak into the spaces between the air sacs and eventually into the sacs themselves. Collapse of many alveoli (a condition called atelectasis Atelectasis Atelectasis is a condition in which all or part of a lung becomes airless and collapses. Blockage of the bronchial tubes is a common cause of atelectasis. Shortness of breath can develop if... read more ) may also result because of a reduction in surfactant, a liquid that coats the inside surface of the alveoli and helps to keep them open.

Fluid in the alveoli and the collapse of many alveoli interfere with the movement of oxygen from inhaled air into the blood. Thus, the level of oxygen in the blood decreases sharply. Movement of carbon dioxide from the blood to air that is exhaled is affected less, and the level of carbon dioxide in the blood changes very little. Because respiratory failure in ARDS results mainly from low levels of oxygen, it is considered hypoxemic respiratory failure Causes Respiratory failure is a condition in which the level of oxygen in the blood becomes dangerously low or the level of carbon dioxide in the blood becomes dangerously high. Conditions that block... read more .

The decrease in the level of oxygen in the blood caused by ARDS and the leakage into the bloodstream of certain proteins (cytokines) produced by injured lung cells and white blood cells White Blood Cells The main components of blood include Plasma Red blood cells White blood cells Platelets read more can lead to inflammation and complications in other organs. Failure of several organs (a condition called multiple organ system failure) may also result. Organ failure can begin soon after the start of ARDS or days or weeks later. Additionally, people with ARDS are less able to fight lung infections, and they tend to develop bacterial pneumonia Hospital-Acquired Pneumonia Hospital-acquired pneumonia is lung infection that develops in people who have been hospitalized, typically after about 2 days or more of hospitalization. Many bacteria, viruses, and even fungi... read more .

ARDS usually develops within 24 to 48 hours of the original injury or disease but may take as long as 4 or 5 days to occur. The person first has shortness of breath, usually with rapid, shallow breathing.

Using a stethoscope, a doctor may hear crackling or wheezing sounds in the lungs. The skin may become mottled or blue (cyanosis Cyanosis Cyanosis is a bluish discoloration of the skin resulting from an inadequate amount of oxygen in the blood. Cyanosis occurs when oxygen-depleted (deoxygenated) blood, which is bluish rather than... read more ) in light-skinned people and gray or whitish coloration in the mouth, around the eyes, and under the nails in dark-skinned people because of low oxygen levels in the blood. Other organs such as the heart and brain may malfunction, resulting in a rapid heart rate, abnormal heart rhythms Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more (arrhythmias), confusion, and sleepiness.

The level of oxygen in the blood can be measured without taking a blood sample by using a sensor placed on a finger or an earlobe—a procedure called pulse oximetry Pulse oximetry Both arterial blood gas testing and pulse oximetry measure the amount of oxygen in the blood, which helps determine how well the lungs are functioning. Arterial blood gas tests are invasive... read more . The level of oxygen (along with carbon dioxide) in the blood can also be measured by analyzing a blood sample taken from an artery.

Chest x-rays show fluid in spaces that should be filled with air. Further tests may be needed to ensure that heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more is not the cause of the problem.

Without prompt treatment, many people who have ARDS will not survive. However, depending upon the underlying disorder, with appropriate treatment, about 60 to 75% of people with ARDS survive.

People who respond promptly to treatment usually recover completely with few or no long-term lung abnormalities. Those whose treatment involves long periods on a ventilator (a machine that helps air get in and out of the lungs) are more likely to develop lung scarring. Such scarring may decrease over a few months after the person is taken off the ventilator. Lung scarring, if extensive, can impair lung function permanently in ways that are noticeable during certain day-to-day activities. Less extensive scarring may impair lung function only when the lungs are stressed, such as during exercise or an illness.

Many people lose large amounts of weight and muscle during the illness. Rehabilitation Pulmonary Rehabilitation Pulmonary rehabilitation is the use of supervised exercise, education, support, and behavioral intervention to improve how people with chronic lung disease function in daily life and to enhance... read more in the hospital can help them regain their strength and independence.

People with ARDS are treated in an intensive care unit Types of units People who need specific types of care may be put in special care units. Intensive care units (ICUs) are for people who are seriously ill. These people include those who have had a sudden, general... read more (ICU).

Successful treatment usually depends on treating the underlying disorder (for example, pneumonia). Oxygen therapy Oxygen Therapy Oxygen therapy is a treatment that delivers extra oxygen to the lungs when the level of oxygen in the blood is too low. Oxygen is a gas that makes up about 21% of the air we breathe. The lungs... read more , which is vital to correcting low oxygen levels, also is given.

If oxygen delivered by a face mask or other device (such as a helmet or nasal prongs) does not correct the low blood oxygen levels, or if very high doses of inhaled oxygen are required, mechanical ventilation Mechanical Ventilation Mechanical ventilation is use of a machine to aid the movement of air into and out of the lungs. Some people with respiratory failure need a mechanical ventilator (a machine that helps air get... read more must be used. Usually a ventilator delivers oxygen-rich air under pressure using a tube inserted through the mouth into the windpipe (trachea).