Respiratory Failure Causes, Signs, Symptoms, Diagnosis, Treatment

Respiratory Failure Causes, Signs, Symptoms, Diagnosis, Treatment


What is respiratory failure?


Respiratory failure is the inability of the respiratory system to supply oxygen or remove carbon dioxide, resulting in low blood oxygen or high blood carbon dioxide levels, respectively. Multiple conditions can cause one or both of these problems. Acute or sudden respiratory failure can happen as the result of trauma, injury, drug or alcohol overdose, or inhalation of carbon monoxide. Chronic, or long-term, respiratory failure is commonly caused by chronic obstructive pulmonary disease (COPD), neuromuscular disease, or even morbid obesity.

Almost everyone who has a critically ill friend or relative may expect to hear the term, respiratory failure. Although failure to breathe normally was recognized even in ancient times as an ominous sign, the term, "respiratory failure," did not appear in the medical literature until the 1960s. Doctors now understand that respiratory failure is a serious disorder caused by a variety of different medical problems that may or may not start in the lung. Healthy people as well as patients with either pulmonary (lung) or nonpulmonary diseases can develop respiratory failure. 

The recognition of respiratory failure as a life-threatening problem led to the development of the concept of the intensive care unit (ICU) in modern hospitals. ICU personnel and equipment support vital functions to give patients their best chance for recovery. Today's sophisticated ICU facilities with their novel mechanical life support devices evolved as doctors and scientists learned more and more about the causes of respiratory failure and how to treat it. 

The signs and symptoms of respiratory failure differ depending on the severity and underlying cause. Acute respiratory failure occurs rapidly and can resolve with treatment. Chronic respiratory failure, on the other hand, is a progressive disease, which typically worsens over time. Symptoms of respiratory failure include difficulty breathing, cyanosis (blue or purple coloration of the skin), and lethargy. Treatment depends on the severity of the disease and may include oxygen support, bronchodilators, and ventilatory support.

Respiratory failure can be a serious or life-threatening condition. Seek immediate medical care if you, or someone you are with, have serious symptoms, such as severe difficulty breathing; severe sharp chest pain; bluish coloration of the lips or fingernails; a change in level of consciousness or alertness, such as passing out or unresponsiveness; and rapid heart rate.

Seek prompt medical care if you are being treated for respiratory failure but mild symptoms recur or are persistent.

What causes respiratory failure?


Respiratory failure is the inability of the respiratory system to supply oxygen or remove carbon dioxide, resulting in low blood oxygen or high blood carbon dioxide levels. Multiple conditions can cause one or both of these problems. Respiratory failure can transpire quickly as the result of trauma, injury, drug or alcohol overdose, or inhalation of carbon monoxide. Chronic, or long-term, respiratory failure is commonly caused by chronic obstructive pulmonary disease (COPD), neuromuscular disease, or even morbid obesity.

Causes of acute respiratory failure


A number of conditions may cause acute respiratory failure, many of which are life-threatening or serious conditions. Examples include:
  • Acute asthma attack
  • Acute respiratory distress syndrome (life-threatening respiratory condition)
  • Carbon dioxide poisoning
  • Chest trauma
  • Drug or alcohol overdose
  • Pneumonia
  • Pneumothorax (collapsed lung)
  • Pulmonary embolism (blockage of one of the main arteries going to the lungs)
  • Smoke inhalation

Causes of chronic respiratory failure


A number of conditions may cause chronic respiratory failure, many of which are serious conditions. Examples include:
  • Amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig’s disease; a severe neuromuscular disease that causes muscle weakness and disability)
  • Chronic obstructive pulmonary disease (COPD), including emphysema and chronic bronchitis
  • Cystic fibrosis (buildup of thick mucus in the lungs and digestive tract)
  • Guillain-BarrĂ© syndrome (autoimmune nerve disorder)
  • Morbid obesity
  • Myasthenia gravis (autoimmune neuromuscular disorder that causes muscle weakness)
  • Sarcoidosis (inflammatory disease most commonly affecting the lungs, skin and eyes)
  • Severe curvature of the spine (scoliosis)

Who Can Get Respiratory Failure


Many different medical conditions can lead to respiratory failure. Listed below are a few examples of people who may develop respiratory failure.
  • A patient with a long history of asthma, emphysema, or chronic obstructive lung disease
  • A patient who is undergoing major surgery in the abdomen, heart, or lung
  • A person who has taken an overdose of sleeping pills or certain depressant drugs
  • A premature baby who weighs less than 3 pounds
  • A baby with bronchopulmonary dysplasia
  • A patient suffering from AIDS
  • A person who has received multiple physical injuries
  • A person who has suffered extensive burns
  • A person who has bled extensively from a gunshot wound
  • A person who has almost drowned
  • A patient with severe heart failure
  • A patient with severe infections
  • A person who is extremely obese

What Are the Signs and Symptoms of Respiratory Failure?


The signs and symptoms of respiratory failure depend on its underlying cause and the levels of oxygen and carbon dioxide in the blood.

A low oxygen level in the blood can cause shortness of breath and air hunger (feeling like you can't breathe in enough air). If the level of oxygen is very low, it also can cause a bluish color on the skin, lips, and fingernails. A high carbon dioxide level can cause rapid breathing and confusion.

Common symptoms of respiratory failure


  • Respiratory failure is accompanied by a number of symptoms including:
  • Bluish coloration of the lips or fingernails
  • Confusion or loss of consciousness
  • Fainting or change in level of consciousness or lethargy
  • Fatigue
  • Irregular heart rate (arrhythmia)
  • Rapid breathing (tachypnea) or shortness of breath

Serious symptoms that might indicate a life-threatening condition


In some cases, respiratory failure can be life threatening. Seek immediate medical care if you, or someone you are with, have any of these life-threatening symptoms including:
  • Bluish coloration of the lips or fingernails
  • Change in level of consciousness or alertness, such as passing out or unresponsiveness
  • Rapid heart rate (tachycardia)
  • Respiratory or breathing problems, such as shortness of breath, difficulty breathing, labored breathing, wheezing, not breathing, or choking

What Happens During Respiratory Failure


When the process of gas exchange is faulty, there is not enough oxygen in the blood (hypoxemia) to fuel the body's metabolic activity. In addition, sometimes there is also an accumulation of carbon dioxide, a waste product of metabolism, in the blood and tissues (hypercapnia). Hypercapnia makes blood more acidic; this condition is called acidemia. Eventually the body tissues become acidic. This condition, called acidosis, injures the body's cells and interferes with the functions of the heart and central nervous system. Ultimately, lack of oxygen in the blood causes death of the cells in the brain and other tissues. If not adequately treated, respiratory failure is fatal. 

Hypoxemic Respiratory Failure


When a lung disease causes respiratory failure, gas exchange is reduced because of changes in ventilation (the exchange of air between the lungs and the atmosphere), perfusion (blood flow), or both. Activity of the respiratory muscles is normal. This type of respiratory failure which results from a mismatch between ventilation and perfusion is called hypoxemic respiratory failure. Some of the alveoli get less fresh air than they need for the amount of blood flow, with the net result of a fall in oxygen in the blood. These patients tend to have more difficulty with the transport of oxygen than with removing carbon dioxide. They often overbreathe (hyperventilate) to make up for the low oxygen, and this results in a low CO2 level in the blood (hypocapnia). Hypocapnia makes the blood more basic or alkaline which is also injurious to the cells. 

If not adequately treated, respiratory failure is fatal. 

Hypercapnic Respiratory Failure


Respiratory failure due to a disease of the muscles used for breathing ("pump or ventilatory apparatus failure") is called hypercapnic respiratory failure. The lungs of these patients are normal. This type of respiratory failure occurs in patients with neuromuscular diseases such as myasthenia gravis, stroke, cerebral palsy, poliomyelitis, amyotrophic lateral sclerosis, muscular dystrophy, postoperative situations limiting ability to take deep breaths, and in depressant drug overdoses. Each of these disorders involves a loss or decrease in neuromuscular function, inefficient breathing and limitation to the flow of air into the lungs. Blood oxygen falls and the carbon dioxide increases because fresh air is not brought into the alveoli in needed amounts. In general, mechanical devices that help move the chest wall help these patients. 

Conditions That May Progress To Respiratory Failure


Almost all lung diseases including asthma, chronic obstructive pulmonary disease (COPD), AIDS-related pneumonia, other pneumonias and lung infections, and cystic fibrosis may eventually lead to respiratory failure particularly if the diseases are inadequately treated. These patients find it very hard to breathe and the result is low oxygen and high carbon dioxide blood levels. 

People whose normal lungs have been injured, such as from exposure to noxious gases, steam, or heat during a fire, can subsequently go into respiratory failure. Adult respiratory distress syndrome (ARDS), also referred to as acute respiratory distress syndrome, is a form of acute respiratory failure caused by extensive lung injury following a variety of catastrophic events such as shock, severe infection, and burns. ARDS can occur in individuals with or without previous lung disease. 

Hyaline membrane disease or respiratory distress syndrome of the newborn (RDS), the most common respiratory illness affecting premature babies, is another kind of respiratory failure. In this condition, the baby's lungs do not have enough surfactant, a substance that makes it possible for air to pass into the alveoli by lowering surface tension and preventing their collapse. 

How Is Respiratory Failure Diagnosed?


Your doctor will diagnose respiratory failure based on your medical history, a physical exam, and test results. Once respiratory failure is diagnosed, your doctor will look for its underlying cause.

Medical History


Your doctor will ask whether you might have or have recently had diseases or conditions that could lead to respiratory failure. 

Examples include disorders that affect the muscles, nerves, bones, or tissues that support breathing. Lung diseases and conditions also can cause respiratory failure.

Physical Exam


During the physical exam, your doctor will look for signs of respiratory failure and its underlying cause.

Respiratory failure can cause shortness of breath, rapid breathing, and air hunger (feeling like you can't breathe in enough air). Using a stethoscope, your doctor can listen to your lungs for abnormal sounds, such as crackling.

Your doctor also may listen to your heart for signs of an arrhythmia (irregular heartbeat). An arrhythmia can occur if your heart doesn't get enough oxygen.

Your doctor might look for a bluish color on your skin, lips, and fingernails. A bluish color means your blood has a low oxygen level.

Respiratory failure also can cause extreme sleepiness and confusion, so your doctor might check how alert you are.

Diagnostic Tests


To check the oxygen and carbon dioxide levels in your blood, you may have:  

  • Pulse oximetry. For this test, a small sensor is attached to your finger or ear. The sensor uses light to estimate how much oxygen is in your blood.
  • Arterial blood gas test. This test measures the oxygen and carbon dioxide levels in your blood. A blood sample is taken from an artery, usually in your wrist. The sample is then sent to a laboratory, where its oxygen and carbon dioxide levels are measured.
A low level of oxygen or a high level of carbon dioxide in the blood (or both) is a possible sign of respiratory failure.

Your doctor may recommend other tests, such as a chest x ray, to help find the underlying cause of respiratory failure. A chest x ray is a painless test that takes pictures of the structures inside your chest, such as your heart, lungs, and blood vessels.

If your doctor thinks that you have an arrhythmia as a result of respiratory failure, he or she may recommend an EKG (electrocardiogram). An EKG is a simple, painless test that detects and records the heart's electrical activity.

How Is Respiratory Failure Treated?


Treatment for respiratory failure depends on whether the condition is acute (short-term) or chronic (ongoing) and its severity. Treatment also depends on the condition's underlying cause.

Acute respiratory failure can be a medical emergency. It often is treated in an intensive care unit at a hospital. Chronic respiratory failure often can be treated at home. If chronic respiratory failure is severe, your doctor may recommend treatment in a long-term care center.

One of the main goals of treating respiratory failure is to get oxygen to your lungs and other organs and remove carbon dioxide from your body. Another goal is to treat the underlying cause of the condition.

Management Of Respiratory Failure


The patient with respiratory failure cannot be adequately treated in the general care areas of the hospital. Therefore, patients in severe respiratory failure are usually treated in the intensive care unit. Current therapy for all forms of respiratory failure attempts, first, to provide support for the heart, lungs, and other affected vital organs; and second, to identify and treat the underlying cause. 

Since the immediate threat to patients with respiratory failure is due to the inadequate level of oxygen delivered to the tissues, oxygenation is the basic therapy for acute respiratory failure due to lung disease. Oxygen-enriched air is usually given to the patient by nasal prongs, oxygen mask, or by placing an airtube into the trachea (windpipe). Since prolonged high oxygen levels can be toxic, the concentration of oxygen must be carefully controlled for both short- and long-term treatment. Assisted ventilation with mechanical devices may be the first priority for neuromuscular disease patients going into respiratory failure. Additional treatments employ ventilation which helps to keep the lungs inflated at low lung volumes (positive end-expiratory pressure, PEEP), and fluid and nutritional management. 

Endotracheal Intubation


Endotracheal intubation involves insertion of a tube into the trachea. It permits delivery of precisely determined amounts of oxygen to the lungs and removal of secretions, and ensures adequate ventilation. Combined with mechanical ventilation, endotracheal intubation is the cornerstone of therapy for respiratory failure. 

Mechanical Ventilation


If the patient is tiring despite ongoing therapy, a mechanical ventilator, also called a respirator, is used. The ventilator assists or controls the patient's breathing. 

Positive End-Expiratory Pressure (PEEP)


Positive end-expiratory pressure is used with mechanical ventilation to keep the air pressure in the trachea at a level that increases the volume of gas remaining in the lung after breathing out (expiration). This keeps the alveoli open, reduces the shunting of blood through the lungs, and improves gas exchange. Most ventilators have a PEEP adjustment. 

Extracorporeal Membrane Oxygenator (ECMO)


The extracorporeal membrane oxygenator (ECMO) is essentially an artificial lung. It is an appropriately cased artificial membrane which is attached to the patient externally (extracorporeally), through a vein or artery. Although the best substitute for a diseased lung that cannot handle gas exchange adequately is a healthy human lung, such substitution is often not possible. Circulating the patient's blood through the ECMO offers another approach. Gas exchange using ECMO keeps the patient alive while the damaged lungs have a chance to heal. 

In 1974, the National Heart, Lung, and Blood Institute (NHLBI) organized a carefully designed clinical trial, to determine the effectiveness of ECMO for patients with acute respiratory distress syndrome. In this study, ECMO appeared to be no more useful than conventional therapy. On the other hand, ECMO seems to be an effective option in some infants with respiratory failure when treatment with mechanical ventilation fails. However ECMO is expensive, is associated with nonrespiratory complications, and is available only in a few specialized centers. 

Management of Fluids and Electrolytes


Pulmonary edema, the buildup of abnormal amounts of fluid in the lung tissues, often occurs in respiratory failure. Therefore fluids are carefully managed and monitored to maintain fluid balance and avoid fluid overload which may further worsen gas exchange. 

Pharmacologic Therapy


Because respiratory failure may be the end result of several different diseases, no single drug therapy is effective in all situations.
  • Antibiotics help when infections (sepsis) as well as pneumonia are involved in respiratory failure.
  • Bronchodilators, for example, theophylline compounds, sympathomimetic agents (albuterol, metaproterenol, isoproterenol), anticholinergics (ipratropium bromide), and corticosteroids, reverse bronchoconstriction and reduce tissue inflammation.
  • Other drugs, such as digitalis, improve cardiac output, and drugs which increase blood pressure in shock can improve blood flow to the tissues.
No single drug therapy is effective in all situations. 

Bronchoscopy


Patients with respiratory failure who have excessive lung secretions are sometimes helped by fiberoptic bronchoscopy, a technique for accessing the interior of the bronchi, the larger air passages of the lungs. The bronchoscope is a flexible tube with a light at the end that is passed through the nose or mouth into the trachea and bronchi. Fluid or tissue can be removed from the bronchi (aspiration), and cells for microscopic examination can be obtained by washing the interior of the larger breathing tubes (lavage). Bronchoscopy is useful for placing or removing endotracheal tubes, removing foreign bodies from the lung, and collecting tissue samples for diagnosis. 

Intravenous Nutritional Support


Nutritional supplementation is essential to maintain or restore strength when weakness and loss of muscle mass prevent patients from breathing adequately without ventilatory support. Appropriate nutrients (fats, carbohydrates, and predigested proteins) are fed intravenously for this purpose. 

Physiotherapy


Physiotherapy includes chest percussion (repeated sharp blows to the chest and back to loosen secretions), suction of airways, and regular changes of body position. It helps drain secretions, maintains alveolar inflation and prevents atelectasis, incomplete expansion of the lung. 

X-ray Monitoring


X-ray images of the chest help the doctor monitor the progress of lung and heart disease in respiratory failure. The portable chest radiograph taken with an x-ray machine brought to the bedside is often used for this purpose in the intensive care unit. 

Lung Transplantation


Lung transplantation currently offers the only hope for certain patients with end-stage pulmonary disease. The shortage of suitable donors and the high cost of the procedure continue to be major obstacles that limit its use. 

Complications of Treatment


Oxygen toxicity, pulmonary embolism (closure of the pulmonary artery or one of its branches by a blood clot or a fat globule), cardiovascular problems, barotrauma (injury to the lung tissue from excessive ventilatory pressure), pneumothorax (air in the pleural space), and gastrointestinal bleeding are some of the complications of treatment. They result from fluid overload, mechanical ventilation, PEEP, and other procedures used in the management of respiratory failure. 

Weaning the Patients From Ventilators


The process of returning the patient to unassisted and spontaneous breathing is called weaning. Weaning is a complex process that requires the understanding and cooperation of the patient. It can cause great fatigue and depression in patients because of the slow- and long-term nature of the treatment procedures. 

Weaning a patient too rapidly or prematurely can be dangerous. Some patients, particularly those who had severe underlying cardiac disease and prolonged episodes of acute illnesses, may require weeks to months to wean. The doctor considers weaning only when the patient is awake, has good nutrition, and is able to cough and breathe deeply. 

Discontinuation of Ventilatory Support


The difficult question of whether and when to discontinue life-sustaining mechanical ventilation to the patient who is not responding to any treatment is sometimes faced by the doctor and the family. The legal, ethical, and financial implications of continuing or withholding treatment to the patient in terminal respiratory failure are important issues addressed at family, professional, and government levels. Respecting the rights and wishes of the patient and helping the patient achieve a dignified and peaceful end while continuing to assure care and comfort is a responsibility shared by both the caregivers and the family. The family with a good understanding of respiratory failure in all its dimensions is best equipped to play its part in sharing this responsibility. 

Living With Respiratory Failure


One of the main goals of treating respiratory failure is to treat the underlying cause of the condition. However, sometimes it's hard to cure or control the underlying cause. Thus, respiratory failure may last for weeks or even years. This is called chronic respiratory failure.

Oxygen therapy and other treatments can help you breathe easier. However, your oxygen and carbon dioxide levels still may not be normal. Thus, you may have one or more of the following symptoms:

  • Shortness of breath
  • Rapid breathing
  • Tiredness and confusion
These symptoms may go away within a few weeks or last longer. Talk with your doctor about how to deal with these symptoms, and read the tips below.

Ongoing Care


If you have respiratory failure, see your doctor for ongoing medical care. Your doctor may refer you to pulmonary rehabilitation (rehab).

Rehab can involve exercise training, education, and counseling. Your rehab team might include doctors, nurses, and other specialists. They'll work with you to create a program that meets your needs.

If you smoke, quit. Talk to your doctor about programs and products that can help you quit smoking. Also, try to avoid secondhand smoke.

If you have trouble quitting smoking on your own, consider joining a support group. Many hospitals, workplaces, and community groups offer classes to help people quit smoking.

If you're on oxygen therapy, don't smoke. Oxygen isn't explosive, but it can worsen a fire. In the presence of oxygen, a small fire can quickly get out of control. Also, the cylinder that compressed oxygen gas comes in can explode when exposed to heat.

For more information about how to quit smoking, go to the Health Topics Smoking and Your Heart article. Although this resource focuses on heart health, it includes basic information about how to quit smoking.

Emotional Issues and Support


Living with respiratory failure may cause fear, anxiety, depression, and stress. Talk about how you feel with your health care team. Talking to a professional counselor also can help. If you're very depressed, your doctor may recommend medicines or other treatments that can improve your quality of life.

Joining a patient support group may help you adjust to living with respiratory failure. You can see how other people who have the same symptoms have coped with them. Talk to your doctor about local support groups or check with an area medical center.

Support from family and friends also can help relieve stress and anxiety. Let your loved ones know how you feel and what they can do to help you.

Prepare for Emergencies


If you have chronic respiratory failure, knowing when and where to seek help for your symptoms is important. You should seek emergency care if you have severe symptoms, such as trouble catching your breath or talking.

Call your doctor if you notice that your symptoms are worsening or if you have new signs and symptoms. Your doctor may change or adjust your treatments to relieve and treat symptoms.

Keep phone numbers handy for your doctor, hospital, and someone who can take you for medical care. You also should have on hand directions to the doctor's office and hospital and a list of all the medicines you're taking.

More About Some Common Lung Diseases Leading to Or Characterized by Respiratory Failure


Asthma 


The hallmarks of asthma are obstruction to air flow and bronchoconstriction, tightening of the muscles in the walls of the bronchi, that is usually relieved by drugs called bronchodilators. Acute asthma attacks that persist, do not respond to bronchodilator therapy, and threaten life are referred to as status asthmaticus. Due to the heavy work of breathing, patients eventually tire and decrease their respiratory efforts. Patients in this condition are prone to develop respiratory failure. Respiratory failure is more common in women with asthma, in patients over 40 years of age, and in patients in whom treatment is delayed, or oral corticosteroid therapy is stopped suddenly. 

During an attack of asthma, airways obstruction from mucus secretions and thickened bronchial tissue can lead to severe hypoxemia, hypercapnia, and acidosis. Other potential complications are pneumonia and accumulation of air in pleural spaces. Patients with hypercapnia are at increased risk of death. 

In children with asthma, respiratory muscle fatigue and interrupted breathing (apnea) are indications of existing or developing respiratory failure. 

Chronic Obstructive Pulmonary Disease (COPD) 


COPD patients may develop acute respiratory failure when their chronic airway obstruction is complicated by infections, pulmonary emboli, heart failure, and drug- induced respiratory depression. Influenza often precipitates respiratory failure even without evidence of pneumonia in COPD patients. The hallmark of respiratory failure in COPD is increasing dyspnea and worsening blood gas abnormalities. Depending on the triggering event, various other clinical features may appear. The most dire sign is a decline in the patient's condition associated with PaO2 of less than 50 mm Hg and a PaCO2 greater than 50 mm Hg during air breathing. Uncontrolled administration of oxygen to patients with COPD and acute respiratory failure without therapy directed at reducing the work of breathing can result in further hypercapnia, acidosis, stupor, and coma. 

Pneumonia 


Patients with very severe pneumonia go into respiratory failure because of lung inflammation and accumulation of fluid that interferes with gas exchange. They breathe hard and become exhausted; their respiratory muscles are unable to keep up the pace. Blood carbon dioxide rises and oxygen in the blood falls further. Sedation, at the time of respiratory stress, may worsen the situation by depression of the brain activity which is needed to keep respiratory muscles working at high levels. This, in turn, decreases the amount of breathing and may promote the development of respiratory failure. 

Respiratory Distress Syndrome of the Newborn 


One type of respiratory failure in the newborn infant, especially those born prematurely, is commonly referred to as "respiratory distress syndrome." It is also called hyaline membrane disease because of the formation of an abnormal, hyaline (glassy and transparent under the microscope), protein-containing membrane in alveoli. RDS may also occur in full-term babies born to diabetic mothers. 

The causes of RDS are complex, but it is believed that the major problem is a poorly developed lung. Surfactant, a unique fat-containing protein necessary to reduce the surface tension in the alveoli of the lung to prevent their collapse, is deficient in RDS babies. The most effective treatment for RDS is the administration of surfactant. Surfactant replacement therapy for RDS, available since 1989, has brought about a 30 percent reduction in death rate for neonatal RDS in the United States (from 89.9 deaths per 100,000 live births in 1989 to 58.3 deaths per 100,000 in 1992). The National Heart, Lung, and Blood Institute (NHLBI) is supporting the development and testing of several different surfactant preparations useful in replacement therapy for RDS. 

Adult or Acute Respiratory Distress Syndrome 


Acute respiratory failure in adults as a clinical entity was first reported in 1967. Respiratory failure usually occurred following a catastrophic event in individuals with no previous lung disease and who did not respond to ordinary methods of respiratory support. Regardless of the event causing the lung injury, the patients exhibited common signs and symptoms, x-ray findings, and tissue changes. Because many of its features resembled the respiratory distress syndrome of the newborn, RDS, the adult disease was called "ARDS." As with RDS, there is increasing evidence that loss of surfactant function may also be associated with ARDS. 

Inhalation of gastric contents (aspiration), pulmonary infections, shock, trauma, burns, extrapulmonary sepsis, inhalation of toxic gases, drug overdose, and near-drowning are some of the different situations that can cause ARDS. An estimated 150,000 cases of ARDS occur yearly in the United States. The estimated mortality rate of ARDS is 50-70 percent. 

ARDS is often associated with multiple organ failure (heart, liver, kidneys, and lungs). Patient survival usually depends on the number of organs which fail, the degree and nature of damage, and the age and previous health status of the patient. The incidence of multiple organ failure is particularly high when sepsis or hypotension from loss of blood are the underlying causes of ARDS.