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Alternative Names :
Non-cardiogenic pulmonary edema; Increased-permeability pulmonary edema; Stiff lung; Shock lung; Adult respiratory distress syndrome; Acute respiratory distress syndrome; Acute lung injury.
Definition:
Acute respiratory distress syndrome (ARDS) is breathing failure that can occur in critically ill persons with underlying illnesses. It is not a specific disease. Instead, it is a life-threatening condition that occurs when there is severe fluid buildup in both lungs. The fluid buildup prevents the lungs from working properly—that is, allowing the transfer of oxygen from air into the body and carbon dioxide out of the body into the air.
In ARDS, the tiny blood vessels (capillaries) in the lungs or the air sacs (alveoli (al-VEE-uhl-eye)) are damaged because of an infection, injury, blood loss, or inhalation injury. Fluid leaks from the blood vessels into air sacs of the lungs. While some air sacs fill with fluid, others collapse. When the air sacs collapse or fill up with fluid, the lungs can no longer fill properly with air and the lungs become stiff. Without air entering the lungs properly, the amount of oxygen in the blood drops. When this happens, the person with ARDS must be given extra oxygen and may need the help of a breathing machine.
Breathing failure can occur very quickly after the condition begins. It may take only 1 or 2 days for fluid to build up. The process that causes ARDS may continue for weeks. If scarring occurs, this will make it harder for the lungs to take in oxygen and get rid of carbon dioxide.
In the past, only about 4 out of 10 people who developed ARDS survived. But today, with good care in a hospital’s intensive or critical care unit, many people (about 7 out of 10) with ARDS survive. Although many people who survive ARDS make a full recovery, some survivors have lasting damage to their lungs.
How the Lungs Work
To understand acute respiratory distress syndrome (ARDS), it is helpful to understand how your lungs work.
Normal Lung Function
A slice of normal lung looks like a pink sponge—filled with tiny bubbles or holes. Around each bubble is a fine network of tiny blood vessels. These bubbles, which are surrounded by blood vessels, give the lungs a large surface to exchange oxygen (into the blood where it is carried throughout the body) and carbon dioxide (out of the blood). This process is called gas exchange. Healthy lungs do this very well.
Here’s how normal breathing works:
- You breathe in air through your nose and mouth. The air travels down through your windpipe (trachea) through large and small tubes in your lungs called bronchial (BRON-kee-ul) tubes. The larger tubes are bronchi (BRONK-eye), and the smaller tubes are bronchioles (BRON-kee-oles). Sometimes, we use the word “airways” to refer to the various tubes or passages that air uses to travel from the nose and mouth into the lungs. The airways in your lungs look something like an upside-down tree with many branches.
- At the ends of the small bronchial tubes, there are groups of tiny bubbles called air sacs or alveoli. The bubbles have very thin walls, and small blood vessels called capillaries are next to them. Oxygen passes from the air sacs into the blood in these small blood vessels. At the same time, carbon dioxide passes from the blood into the air sacs.
Causes:
The causes of acute respiratory distress syndrome (ARDS) are not well understood. It can occur in many situations and in persons with or without a lung disease.
ARDS can be caused by any major lung inflammation or injury. Some common causes include pneumonia, septic shock, trauma, aspiration of vomit, or chemical inhalation. ARDS develops as inflammation and injury to the lung and causes a buildup of fluid in the air sacs. This fluid inhibits the passage of oxygen from the air into the bloodstream.
The fluid buildup also makes the lungs heavy and stiff, and the lungs’ ability to expand is severely decreased. Blood concentration of oxygen can remain dangerously low in spite of supplemental oxygen delivered by a mechanical ventilator (breathing machine) through an endotracheal tube (breathing tube).
Typically patients require care in an intensive care unit (ICU). Symptoms usually develop within 24 to 48 hours of the original injury or illness. 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.
There are two ways that lung injury leading to ARDS can occur: through a direct injury to the lungs, or indirectly when a person is very sick or has a serious bodily injury. However, most sick or badly injured persons do not develop ARDS.
Direct Lung Injury
A direct injury to the lungs may result from breathing in harmful substances or an infection in the lungs. Some direct lung injuries that can lead to ARDS include:
- Severe pneumonia (infection in the lungs)
- Breathing in vomited stomach contents
- Breathing in harmful fumes or smoke
- A severe blow to the chest or other accident that bruises the lungs
Indirect Lung Injury
Most cases of ARDS happen in people who are very ill or who have been in a major accident. This is sometimes called an indirect lung injury. Less is known about how indirect injuries lead to ARDS than about how direct injuries to the lungs cause ARDS. Indirect lung injury leading to ARDS sometimes occurs in cases of:
- Severe and widespread bacterial infection in the body (sepsis)
- Severe injury with shock
- Severe bleeding requiring blood transfusions
- Drug overdose
- Inflamed pancreas
It is not clear why some very sick or seriously injured people develop ARDS, and others do not. Researchers are trying to find out why ARDS develops and how to prevent it.
Pollution: Checking the Damages Caused to the Respiratory System
Symptoms:
*Shortness of breath
*Fast, labored breathing
*A bluish skin color (due to a low level of oxygen in the blood)
*A lower amount of oxygen in the blood
*Labored, rapid breathing
*Low blood pressure or shock (low blood pressure accompanied by organ failure)
Often, persons affected by ARDS are so sick they are unable to complain of symptoms.
Doctors and other health care providers watch for these signs and symptoms in patients who have conditions that might lead to ARDS. People who develop ARDS may be too sick to complain about having trouble breathing or other related symptoms. If a patient shows signs of developing ARDS, doctors will do tests to confirm that ARDS is the problem.
ARDS is often associated with the failure of other organs and body systems, including the liver, kidneys, and the immune system. Multiple organ failure often leads to death.
Effects of ARDS
In ARDS, the tiny blood vessels leak too much fluid into the lungs. This results from toxins (poisons) that the body produces in response to the underlying illness or injury. The lungs become like a wet sponge, heavy and stiffer than normal. They no longer provide the effective surface for gas exchange, and the level of oxygen in the blood falls. If ARDS is severe and goes on for some time, scar tissue called fibrosis may form in the lungs. The scarring also makes it harder for gas exchange to occur.
People who develop ARDS need extra oxygen and may need a breathing machine to breathe for them while their lungs try to heal. If they survive, ARDS patients may have a full recovery. Recovery can take weeks or months. Some ARDS survivors take a year or longer to recover, and some never completely recover from having ARDS.
Who Is At Risk for ARDS?
Acute respiratory distress syndrome (ARDS) usually affects people who are being treated for another serious illness or those who have had major injuries. It affects about 150,000 people each year in the United States. ARDS can occur in people with or without a previous lung disease. People who have a serious accident with a large blood loss are more likely to develop ARDS. However, only a small portion of people who have problems that can lead to ARDS actually develop it.
In most cases, a person who develops ARDS is already in the hospital being treated for other medical problems. Some illnesses or injuries that can lead to ARDS include:
- Serious, widespread infection in the body (sepsis)
- Severe injury (trauma) and shock from a car crash, fire, or other cause
- Severe bleeding that requires blood transfusions
- Severe pneumonia (infection of the lungs)
- Breathing in vomited stomach contents
- Breathing in smoke or harmful gases and fumes
- Injury to the chest from trauma (such as a car accident) that causes bruising of the lungs
- Nearly drowning
- Some drug overdoses
Diagnosis:
Doctors diagnose acute respiratory distress syndrome (ARDS) when:
- A person suffering from severe infection or injury develops breathing problems.
- A chest x ray shows fluid in the air sacs of both lungs.
- Blood tests show a low level of oxygen in the blood.
- Other conditions that could cause breathing problems have been ruled out.
ARDS can be confused with other illnesses that have similar symptoms. The most important is congestive heart failure. In congestive heart failure, fluid backs up into the lungs because the heart is weak and cannot pump well. However, there is no injury to the lungs in congestive heart failure. Since a chest x ray is abnormal for both ARDS and congestive heart failure, it is sometimes very difficult to tell them apart.
Exams and Tests :
Chest auscultation (examination with a stethoscope) 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 frequently seen.
Tests used in the diagnosis of ARDS include:
- Chest X-ray
- Arterial blood gas
- CBC and blood chemistries
- Evaluation for possible infections
- Cultures and analysis of sputum specimens
Occasionally an echocardiogram (heart ultrasound) or Swan-Ganz catheterization may need to be done to exclude congestive heart failure, which can have a similar chest X-ray appearance to ARDS.
Treatment: Patients with acute respiratory distress syndrome (ARDS) are usually treated in the intensive or critical care unit of a hospital. The main concern in treating ARDS is getting enough oxygen into the blood until the lungs heal enough to work on their own again. The following are important ways that ARDS patients are treated.
The objective of treatment is to provide enough support for the failing respiratory system (and other systems) until these systems have time to heal. Treatment of the underlying condition that caused ARDS is essential.
The main supportive treatment of the failing respiratory system in ARDS is mechanical ventilation (a breathing machine) to deliver high doses of oxygen and a continuous level of pressure called PEEP (positive end-expiratory pressure) to the damaged lungs.
The high pressures and other breathing machine settings required to treat ARDS often require that the patient be deeply sedated with medications.
This treatment is continued until the patient is well enough to breathe on his or her own. Medications may be needed to treat infections, reduce inflammation, and eliminate fluid from the lungs.
Modern Medications:
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 and from “fighting” the breathing machine
- Drugs to raise blood pressure or stimulate the heart
- Muscle relaxers to prevent movement and reduce the body’s demand for oxygen
Other Treatment
With breathing tubes in place, ARDS patients cannot eat or drink as usual. They must be fed through a feeding tube placed through the nose and into the stomach. If this does not work, feeding is done through a vein. Sometimes a special bed or mattress, such as an airbed, is used to help prevent complications such as pneumonia or bedsores. If complications occur, the patient may require treatment for them.
Results
With treatment:
- Some patients recover quickly and can breathe on their own within a week or so. They have the best chance of a full recovery.
- Patients whose underlying illness is more severe may die within the first week of treatment.
- Those who survive the first week but cannot breathe on their own may face many weeks on the breathing machine. They may have complications and a slow recovery if they survive.
Acute Respiratory Distress Syndrome
Prognosis :
The death rate in ARDS is approximately 30%. Although survivors usually recover normal lung function, many individuals suffer permanent, usually mild, lung damage.
Many people who survive ARDS suffer memory loss or other problems with thinking after they recover. This is related to brain damage caused by reduced access to oxygen while the lungs were malfunctioning.
After going home from the hospital, the ARDS survivor may need only a little or a lot of help. While recovering from ARDS at home, a person may:
- Need to use oxygen at home or when going out of the home, at least for a while
- Need to have physical, occupational, or other therapy
- Have shortness of breath, cough, or phlegm (mucus)
- Have hoarseness from the breathing tube in the hospital
- Feel tired and not have much energy
- Have muscle weakness
Calling Your Health Care Provider
Usually, ARDS occurs in the setting of another illness, for which the patient is already in the hospital. Occasionally, a healthy person may develop severe pneumonia that progresses to ARDS. If breathing difficulty develops, call the local emergency number (such as 911) or go to the emergency room.
Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose
Resources:
http://www.nlm.nih.gov/medlineplus/ency/article/000103.htm
http://www.nhlbi.nih.gov/health/dci/Diseases/Ards/Ards_WhatIs.html
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