Definition
Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition, a form of breathing failure in very ill or severely injured people. It is not a specific disease. It starts with swelling of lung tissue and fluid building up in the tiny air sacs that move oxygen into the bloodstream, which drives blood oxygen down. It resembles infant respiratory distress syndrome, but the causes and treatments differ. ARDS can develop in anyone over the age of 1 year. Also called adult respiratory distress syndrome or respiratory distress syndrome.
Causes
Direct injury to the lungs: chest trauma such as a heavy blow, breathing vomit, breathing smoke, chemicals, or salt water, and burns.
Indirect injury to the lungs: severe infection, massive blood transfusion, pneumonia, severe inflammation of the pancreas (pancreatitis), overdoses of alcohol or certain drugs (aspirin, cocaine, opioids, phenothiazines, tricyclic antidepressants), and lung or bone marrow transplantation. Within a few days of a lung transplant the recipient is prone to ARDS.
Risk Factors
ARDS usually develops in people already hospitalized and being treated for one of the injuries above, though only a small number of them actually develop it. No one can predict who will, but cigarette smokers, those with chronic lung disease, and those over age 65 are more at risk.
Symptoms
Shortness of breath, fast labored breathing, bluish skin or fingernail color, and rapid pulse.
Diagnosis
Suspect ARDS when a patient with severe infection or injury develops breathing problems, a chest x-ray shows fluid in the air sacs of both lungs, blood tests show low blood oxygen, and other causes of breathing trouble have been ruled out. Workup includes blood pressure check; blood tests for oxygen levels, signs of infection, and BNP (brain natriuretic peptide, a marker of heart failure); chest x-ray; analysis of coughed-up matter; sometimes an echocardiogram (heart ultrasound) to rule out congestive heart failure; pulmonary artery catheterization to aid the workup; and bronchoscopy to analyze the airways, where lab examination may show certain viruses or cancer cells. Open lung biopsy is reserved for cases that are hard to diagnose.
How ARDS Is Defined and Graded
The current standard is the Berlin Definition (2012), which requires that symptoms begin within one week of a known clinical insult, that chest imaging shows bilateral opacities not fully explained by effusions or collapse, and that the respiratory failure is not fully explained by heart failure or fluid overload. The older split between "acute lung injury" and ARDS was dropped in favor of three severity grades based on the PaO2/FiO2 ratio measured with at least 5 cm H2O of PEEP: mild (200 to 300), moderate (100 to 200), and severe (less than 100). Severity tracks with outcome, with reported mortality of roughly 27%, 32%, and 45% across the mild, moderate, and severe groups (StatPearls). These grades are based on the adult definition; a separate pediatric definition exists for children.
Nursing Diagnoses
- Ineffective airway clearance
- Ineffective breathing pattern
- Impaired gas exchange
- Anxiety
Treatment
Treat the underlying cause or injury and support the patient until the lungs heal. Support means mechanical ventilation through a tube placed in the mouth or nose or through an opening in the neck, monitoring blood chemistry and fluid levels, and sedation, which most ARDS patients need to tolerate these treatments.
Frequently Asked Questions
What is ARDS in simple terms? ARDS is sudden, severe breathing failure in someone who is already very ill or badly injured. Fluid leaks into the tiny air sacs of both lungs and surfactant breaks down, so the lungs cannot move enough oxygen into the blood (NHLBI).
What causes ARDS? It follows a direct lung injury (aspiration, inhaled smoke or chemicals, near-drowning, chest trauma, pneumonia) or an indirect insult (sepsis, severe pancreatitis, massive transfusion, certain drug overdoses). Sepsis and pneumonia are among the most common triggers.
How is ARDS diagnosed? By the Berlin Definition: symptoms within one week of a known insult, bilateral opacities on chest imaging, respiratory failure not explained by heart failure or fluid overload, and a low PaO2/FiO2 ratio. Echocardiography or other testing helps rule out a cardiac cause (StatPearls).
What is the difference between ARDS and infant respiratory distress syndrome? They are different conditions. Infant respiratory distress syndrome reflects a surfactant deficiency in premature newborns, while ARDS is an acute inflammatory lung injury that can develop at any age from an outside insult. The causes and treatments differ.
Is ARDS fatal? It can be. Mortality rises with severity, reported at roughly 27% for mild, 32% for moderate, and 45% for severe ARDS, and survivors may have lasting reduced lung function (StatPearls). Early supportive care and treating the cause improve the odds.
How is ARDS treated? Treatment supports oxygenation while the underlying cause is corrected. Most patients need mechanical ventilation, often with lung-protective low tidal volumes, along with careful fluid management, sedation, and treatment of the trigger such as antibiotics for sepsis.