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Jan.20.2021View related content

Acute respiratory distress syndrome in adults


Key Points

  • Acute respiratory distress syndrome is severe and often fatal acute respiratory failure; characterized by diffuse inflammatory lung injury rapidly progressing to increased pulmonary vascular permeability, increased lung weight, and hypoxemia
  • Most commonly secondary to pneumonia, nonpulmonary sepsis, and trauma. Worsening respiratory status most commonly develops within 1 week of clinical insult r1
  • Primary diagnostic tools are arterial blood gas levels showing hypoxemia with a PaO₂ to FIO₂ ratio of 300 mm Hg or less and radiograph showing bilateral opacities; echocardiogram may be required to ascertain that these opacities are not attributable to cardiogenic pulmonary edema r1
  • Treatment is primarily conventional mechanical ventilation using lung-protective strategies (ie, low-tidal-volume and/or low-pressure ventilation) and a high concentration of inspired oxygen and PEEP
  • Other supportive care measures include prone positioning during mechanical ventilation, conservative fluid management strategies, and provision of enteral nutrition to prevent respiratory muscle weakness
  • Additional treatments focus on addressing underlying cause
  • High mortality rate of up to 46%; survivors commonly have residual lung damage r1r2

Urgent Action

  • Conventional mechanical ventilation with low tidal volumes, PEEP, and moderate to high oxygen, with the goal of maximizing oxygenation r3r4
  • Prone positioning decreases mortality r4


  • Early stages can be difficult to differentiate from cardiogenic pulmonary edema, possibly resulting in delay of critical interventions r5
  • An outbreak of lung injury associated with vaping was identified by CDC in September 2019; be aware that severe lung disease, including acute respiratory distress syndrome can occur r6r7


Clinical Clarification

  • Acute respiratory distress syndrome is severe and often fatal acute respiratory failure; characterized by diffuse inflammatory lung injury rapidly progressing to increased pulmonary vascular permeability, increased lung weight, and hypoxemia
  • Preceded by a clinical insult—usually pneumonia, nonpulmonary sepsis, aspiration of gastric contents, or trauma
  • Berlin definition of acute respiratory distress syndrome includes presence of all following criteria: r1
    • Timing of acute onset of symptoms (or worsening of nonacute symptoms) within 1 week of a known clinical insult
    • Hypoxemia as shown by the PaO₂ to FIO₂ ratio of 300 mm Hg or less with PEEP or CPAP of 5 cm H₂O or greater
    • Chest imaging showing bilateral opacities that are not explained by effusions, atelectasis, or nodules, and are not cardiogenic in nature
    • Respiratory failure or pulmonary edema not fully explained by cardiac failure or fluid overload


  • Under conventional mechanical ventilation, the following apply:
    • The 3 categories of acute respiratory distress syndrome are based on degree of hypoxemia, as follows: r1
      • Mild: 200 mm Hg < PaO₂/FIO₂ ≤ 300 mm Hg
      • Moderate: 100 mm Hg < PaO₂/FIO₂ ≤ 200 mm Hg
      • Severe: PaO₂/FIO₂ ≤ 100 mm Hg
    • A minimum PEEP of 5 cm H₂O is required to make the severity classification; it may be delivered noninvasively with CPAP to classify mild cases r1


Clinical Presentation


  • Recent known clinical insult (usually within 3 days and nearly always within 7 days) or new or worsening respiratory symptoms r1c1c2c3
    • Known history of (or recent symptoms suggestive of) congestive heart failure can suggest possibility of cardiogenic (rather than noncardiogenic) pulmonary edema c4
  • Symptoms may vary in severity, with some being mild initially; all worsen over a period of several hours

Physical examination

  • Cyanosis may be evident c13
  • Tachypnea at rest c14
  • Tachycardia at rest c15
  • Hypotension is often present c16
  • Fever may or may not be present, depending on the presence of infection as an underlying cause c17c18
  • Use of accessory muscles of respiration (usually indicates moderate to severe disease) c19c20c21
  • Coarse crepitations of both lungs at presentation c22
  • Cold, mottled extremities with prolonged capillary refill time (longer than 2 seconds) indicates ineffective circulation c23c24c25
  • Evaluate carefully for:
    • Signs of cardiogenic pulmonary edema (which can both mimic and coexist with acute respiratory distress syndrome), including bilateral crackles, jugular venous distention, S₃/S₄ gallop, hepatomegaly, and dependent edema c26c27c28c29c30c31
    • Signs of underlying infection, including pneumonia (egophany, rales, dullness to percussion), lymphadenopathy, and septic emboli of the skin c32c33c34c35

Causes and Risk Factors


  • Direct alveolar injury
    • Pneumonia c36
    • Aspiration of gastric contents c37
    • Near-drowning
    • Noxious inhalation (eg, chlorine, high oxygen) c38c39c40
    • Fat, amniotic fluid, or air emboli
    • Vaping-related injury r8c41
  • Indirect alveolar injury
    • Sepsis (nonpulmonary origin) c42
    • Trauma c43
    • Multiple blood transfusions c44
    • Drug reaction (eg, nitrofurantoin, amiodarone, anticancer drugs) or overdose (eg, opiates) c45c46c47c48
    • Cardiopulmonary bypass c49
    • Burns c50
    • Acute pancreatitis c51

Risk factors and/or associations

  • May occur at any age
  • In trauma patients, progressive increase in risk up to ages 60 through 69 years, with declining risk thereafter r9c52c53c54c55
  • In vaping-related pulmonary disease, most patients are aged 18 to 34 years r7c56
  • In trauma patients, females are at increased risk r10c57c58
  • Mortality rates are higher for Black people than for White people in broad epidemiologic studies r11c59c60
  • When limited to national (United States) trauma data: r12
    • Black race is protective (ie, lower incidence of acute respiratory distress syndrome) c61
    • Hispanic ethnicity is associated with increased acute respiratory distress syndrome–associated mortality c62
Other risk factors/associations
  • Worldwide, sepsis is most common risk factor
  • 60% to 70% of patients with COVID-19 who require intensive care have (or develop) acute respiratory distress syndrome r13
  • Chronic alcohol use disorder significantly increases risk of acute respiratory distress syndrome in patients with critical illness c63

Diagnostic Procedures

Primary diagnostic tools

  • Use history, physical examination findings, arterial blood gas measurements, and imaging studies to diagnose according to Berlin definition r1c64
    • Chest radiography is the initial diagnostic evaluation r1
    • CT is not routine, but is often obtained for more detail
    • Early stages can be difficult to differentiate from cardiogenic pulmonary edema based on history and physical examination, possibly resulting in delay of critical interventions; additional evaluation with transthoracic echocardiogram may be helpful


  • Arterial blood gas measurement r1c65
    • Indicated for diagnosis and ongoing monitoring of all patients in whom the syndrome is suspected
    • Findings include:
      • Varying degrees of hypoxemia
      • Earliest finding is respiratory alkalosis; with progression, respiratory acidosis with hypercapnia
      • Widened alveolar-arterial gradient
    • PaO₂ to FIO₂ ratio is used to assess severity, as follows: r1c66
      • Mild: 200 mm Hg < PaO₂/FIO₂ ≤ 300 mm Hg
      • Moderate: 100 mm Hg < PaO₂/FIO₂ ≤ 200 mm Hg
      • Severe: PaO₂/FIO₂ ≤ 100 mm Hg
  • Routine laboratory tests include CBC, blood chemistries, and coagulation studies; in addition, the following laboratory tests are typically obtained: c67c68c69
    • BNP or N-terminal proBNP (NT-proBNP) (to distinguish cardiogenic from noncardiogenic pulmonary edema) c70c71
      • Result below 100 pg/mL has high specificity (about 95%) for acute respiratory distress syndrome; however, higher levels do not exclude the diagnosis r14
    • Sputum Gram stain and culture c72c73
    • Serum amylase or lipase if acute pancreatitis is suspected c74c75


  • Chest radiography c76
    • Indicated for diagnosis and ongoing monitoring of all patients in whom acute respiratory distress syndrome is suspected r1
      • Within first few hours of precipitating event, lungs may appear normal r1
      • Within 24 hours, bilateral airspace opacities are usually evident r1
      • In severe acute respiratory distress syndrome, airspace opacities are commonly present in 3 or 4 lung quadrants r1
  • CT c77
    • Useful for determining root cause of respiratory symptoms in some cases (eg, cancer, chronic interstitial lung diseases, edema) r1
      • Widespread patchy or coalescent airspace opacities are consistent with acute respiratory distress syndrome
      • Consider risk versus benefit of moving a critically ill patient for CT scan
  • Echocardiography r1c78
    • Objective aid to clinical judgment for excluding cardiogenic pulmonary edema; however, cardiogenic and noncardiogenic pulmonary edema can coexist
    • Findings suggestive of cardiogenic pulmonary edema include significantly reduced left ventricular ejection fraction, diastolic dysfunction, and aortic or mitral valve dysfunction

Differential Diagnosis

Most common

  • Cardiogenic pulmonary edema c79
    • Clinical indicators
      • Abnormal findings on cardiac examination
        • Third heart sound (S₃ gallop)
        • Heart murmurs
        • Irregular heart rate
        • Displaced point of maximum impulse of heart
        • Elevated jugular venous pressure
      • Radiographic abnormalities may overlap with the findings of acute respiratory distress syndrome; abnormalities include:
        • Pulmonary venous congestion
        • Kerley B lines
        • Cardiomegaly
        • Pleural effusions
    • Differentiating features
      • Echocardiography with findings of cardiac dysfunction favors cardiogenic pulmonary edema
      • Plasma brain natriuretic peptide level less than 100 pg/mL favors acute respiratory distress syndrome r14r15
  • Viral or bacterial pneumonitis c80c81
    • Clinical indicators
      • Upper respiratory symptoms may precede illness
      • Fever is likely
    • Differentiating features
      • History, physical examination, and diagnostic test findings will not meet the Berlin definitionr1
      • Sputum microscopy, culture, and/or rapid antigen detection suggest infection
      • Bronchoalveolar lavage with suggestive cytologic changes favors viral pneumonitis
    • In addition to being a possible differential diagnosis, pneumonia is also the most frequent lung condition leading to acute respiratory distress syndrome

Less common

  • Chronic interstitial lung diseases (eg, idiopathic pulmonary fibrosis, occupational lung diseases, autoimmune diseases) c82c83c84c85
    • Clinical indicators
      • Dyspnea and cough slowly progressing over months or years, caused by diffuse alveolar damage
        • However, chronic interstitial lung diseases may sometimes worsen rapidly, mimicking acute respiratory distress syndrome
      • Associated signs/symptoms of the underlying disease (eg, arthralgias or arthritis in autoimmune disease)
      • Early radiographs may reveal subpleural reticular changes mixed with alveolar opacities
    • Differentiating features
      • Slower, progressive onset
      • Will not meet the Berlin definitionr1
      • CT scan may suggest the diagnosis
      • Lung tissue biopsy confirms diagnosis
  • Acute interstitial pneumonitis c86d1
    • Clinical indicators
      • Rapid onset of respiratory failure, which clinically mimics acute respiratory distress syndrome symptomatically and radiologically, but for which no precipitating factor is identified
    • Differentiating features
      • Difficult to differentiate; can be thought of as idiopathic acute respiratory distress syndrome
  • Malignancy c87d2
    • Clinical indicators d3
      • Rapid, progressive cancer disseminating throughout the lungs may have a presentation similar to that of acute respiratory distress syndrome
      • Usually lymphoma or acute leukemia
    • Differentiating features
      • Will not meet the Berlin definitionr1
      • Bronchoalveolar lavage may reveal malignant cells
  • Diffuse alveolar hemorrhage c88
    • Clinical indicators
      • Syndrome presenting with hemoptysis (two-thirds of patients) evolving over days to weeks with progressive anemia, diffuse alveolar infiltrates, and hypoxemic respiratory failure
      • Most commonly associated with underlying connective tissue disorder and less commonly with toxin inhalation or drug reaction
    • Differentiating features
      • Often requires serial bronchoalveolar lavage for diagnosis because symptoms and imaging findings are nonspecific
        • Hemoptysis is absent in one-third of patients and those patients may be indistinguishable from patients with acute respiratory distress syndrome
        • Intra-alveolar RBCs appear in lavage fluid in increasing numbers, with hemosiderin-laden macrophages appearing within 48 to 72 hours
        • CBC shows progressive anemia



  • Maintain oxygenation via mechanical ventilation with adjustments of FiO₂ and PEEP; ARDS Network goal is PaO₂ of 55 to 80 mm Hg or SpO₂ of 88% to 95% r16
  • Avoid ventilator-induced lung damage by using protective (ie, volume-limited and/or pressure-limited) ventilator settings
  • Maintain a neutral or net-negative fluid balance in hemodynamically stable patients
    • Central venous pressure goal of 4 to 8 mm Hg r17
    • Urine output of more than 0.5 mL/kg r17
    • Adequate cardiac output r17
  • Identify and treat or reverse the underlying cause


Admission criteria

Criteria for ICU admission
  • All patients in whom acute respiratory distress syndrome is either confirmed or suspected

Recommendations for specialist referral

  • Refer to pulmonologist or critical care specialist for ventilator management
  • Consult infectious disease specialist if infection is suspected

Treatment Options

Mainstay of treatment is supportive care in an ICU setting

  • Mechanical ventilation using PEEP and a lung-protective strategy of low tidal volumes and airway pressures to mitigate ventilator-induced lung injury r18r19
    • Minority of patients may be managed with noninvasive delivery high FiO₂ (ie, humidified high-flow nasal cannula) r17r20
  • Prone positioning improves mortality in severe cases and should be used as an up-front management strategy rather than as a rescue effort r21r22r23
  • For refractory hypoxemia, extracorporeal membrane oxygenation is associated with a significantly lower 28-day mortality compared with lung-protective ventilation r22
  • Deep sedation to decrease oxygen consumption r24
    • Addition of neuromuscular blockade during mechanical ventilation requires more study, but could be considered for moderate to severe acute respiratory distress syndrome (resulted in a mortality benefit in a clinical trial)
  • Conservative fluid management results in more ventilator-free days and fewer days in the ICU compared with liberal fluid management r25r26
    • Fluid management strategies include use of IV crystalloids, vasopressors (eg, norepinephrine), inotropes (eg, dobutamine), and diuretics (eg, furosemide) to maintain effective tissue perfusion
    • In some cases it may be reasonable to combine a liberal strategy (ie, for resuscitation early in course of disease) with a conservative strategy (ie, later in course of disease) r26
    • Pulmonary artery catheter–guided fluid management is associated with more complications than central venous catheter–guided management and does not improve outcomes; a pulmonary artery catheter should not be routinely used r27
  • Other supportive care, including nutrition and prophylaxis of expected medical complications (eg, deep venous thrombosis, stress ulcers) r28
  • A Cochrane review concluded that there is insufficient evidence to determine with certainty whether corticosteroids, surfactants, N‐acetylcysteine, statins, or β‐agonists are effective at reducing mortality or duration of mechanical ventilation in patients with acute respiratory distress syndrome r29
    • NIH COVID-19 treatment guideline recommends use of dexamethasone in patients who require supplemental oxygen with or without mechanical ventilation r30
    • Corticosteroid therapy has been reported in many cases to be useful in vaping-related lung injury, but no standardized recommendations exist for treatment r6r31

Drug therapy

  • Pharmaceutical interventions should be aimed at:
    • Treating root causes (eg, antibiotics for sepsis or bacterial pneumonia; remdesivir for COVID-19) c89
    • If indicated, maintaining blood pressure and effective tissue perfusion and oxygenation (eg, pressors, inotropes, diuretics) c90c91c92

Nondrug and supportive care

Prone positioning c93

  • General explanation
    • Prone position for severe cases during conventional mechanical ventilation provides significant survival benefit in meta-analyses, although pressure ulcers and airway problems are increased r4r21r23
    • May be especially helpful in subpopulation of patients who are already receiving low-tidal-volume ventilation without improvement
    • Outcomes are best when used in combination with low-tidal-volume ventilation (6 mL/kg) and neuromuscular blockade r21
    • Prone position is maintained for at least 16 hours per day r21
    • 2017 American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline recommends prone positioning for more than 12 hours per day in severe acute respiratory distress syndrome r19
    • Contraindications include facial/neck trauma, spinal instability, recent sternotomy, large ventral surface burn, elevated intracranial pressure, large volume hemoptysis, and high risk for requiring cardiopulmonary resuscitation or defibrillation r21
  • Indication
    • Patients with severe acute respiratory distress syndrome who do not improve with lung-protective ventilator strategies

Careful fluid management c94

  • Includes optimal use of IV crystalloids (ie, fluid boluses and maintenance IV fluid infusions), use of vasopressors (eg, dobutamine), and use of diuretics (eg, furosemide) to maintain effective central and peripheral tissue perfusion and oxygenation
  • Various strategies have been studied and are loosely categorized as conservative (aiming for a lower intravascular pressure and resulting in lower positive cumulative fluid balance) or liberal (aiming for a higher intravascular pressure and resulting in higher positive cumulative fluid balance) r25r26
  • Research-based fluid management protocols for each of these strategies are complex and take into account the goal intravascular pressure (eg, low versus high as measured by central venous pressure or pulmonary artery wedge pressure), mean arterial pressure, urine output, and evidence of adequate peripheral tissue perfusion r32
    • Details of management used in research studies (including a protocol algorithm)r33 are available from the NIH/National Heart Lung and Blood Institute Acute Respiratory Distress Syndrome Networkr32
    • Conservative fluid management results in more ventilator-free days and fewer days in the ICU, compared to liberal fluid management r25
      • Recent study included 3 levels of fluid management: r25
        • Conservative (cumulative fluid balance − 136 mL) r25
        • Simplified/conservative (cumulative fluid balance + 1913 mL) r25
        • Liberal (cumulative fluid balance + 6992 mL) r25
      • Simplified/conservative strategy was considered a safe and effective alternative to a conservative strategy, and both appeared preferable to a liberal fluid strategy r25

Other supportive care

  • Nutritional support r34c95
    • Initiate nutritional support within 24 to 48 hours after intubation
    • Enteral feeding (either gastric or small-bowel) is preferred over total parenteral nutrition when the gastrointestinal tract is functional, owing to fewer complications (eg, infection)
    • No difference in 6- to 12-month outcomes (eg, physical function, survival, multiple secondary outcomes) with initial trophic (small-volume) versus full enteral feeding r35
    • Polymeric formula is preferred; fluid-restricted formulas are available
    • Withhold enteral feedings if patients are hypotensive
  • Deep vein thrombosis prophylaxis using pharmacologic agents according to established clinical practice guidelines r36
  • Gastrointestinal bleeding prophylaxis for patients receiving mechanical ventilation r37r38
Conventional mechanical ventilation using lung-protective strategy c96
General explanation
  • Lung-protective strategies include low-tidal-volume ventilation and/or low-pressure ventilation c97c98
    • Decreased mortality at 28 days, but evidence is insufficient regarding long-term morbidity and quality of life after protective strategy versus conventional strategy r18
    • 2017 American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline recommends mechanical ventilation using lower tidal volumes (4-8 mL/kg predicted body weight) and lower inspiratory pressures (plateau pressure less than 30 cm H₂O) r19
    • Cochrane review found insufficient evidence to confirm or refute any advantage with low-tidal-volume ventilation as compared with low-pressure ventilation r3
    • Low-tidal-volume ventilation
      • Tidal volume of about 6 mL/kg (predicted body weight) is considered low volume, in comparison to usual 8 to 15 mL/kg r39
      • Predicted body weight is about 20% lower than measured body weight and is calculated as:
        • Males (in kg): 50 + 0.91 (height, 152.4 cm) r40
        • Females (in kg): 45.5 + 0.91 (height, 152.4 cm) r40
      • 6 mL/kg volume is recommended by international guidelines for management of patients who develop acute respiratory distress syndrome due to sepsis r39
      • Permissive hypercapnia (which usually accompanies lower tidal volumes) is considered safe and is associated with improved outcomes; ARDS Network goal is pH of 7.3 to 7.45, but many authors advocate allowing pH as low as 7.2 r16r41
      • Mechanical ventilation goals in acute respiratory distress syndrome.From Przybysz TM et al: Early treatment of severe acute respiratory distress syndrome. Emerg Med Clin North Am. 34(1):1-14, 2016, Table 7.
        Tidal volume4-6 mL/kg of ideal body weight
        Plateau pressureIdeally less than 30 cm H₂O but lower may be better
        pH, respiratory rate, minute ventilationDepends on patient comorbidities but pH of 7.2 is widely accepted as acceptable permissive hypercapnia; lower may also be acceptable
        PEEPUnknown; higher may be better for severe ARDS
        FiO₂Unknown; titration based on PEEP to FiO₂ table is appropriate
    • Low-pressure ventilation r18
      • Plateau pressure 30 cm H₂O or less r18
  • Other evidence-based ventilation strategies
    • Use PEEP to improve oxygenation and prevent atelectasis r42c99
      • Set PEEP for at least 5 cm H₂O; higher may be better r42
        • Improves oxygenation; mortality benefit of higher PEEP is limited to patients with more severe acute respiratory distress syndrome r43
        • 2017 American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline recommends higher PEEP in patients with moderate or severe acute respiratory distress syndrome r19
        • No significant increase in the risk of barotrauma with higher PEEP r43
    • Consider using recruitment maneuvers to keep all alveoli open (or to open previously collapsed alveoli) in refractory hypoxemia r42
      • 2017 American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine clinical practice guideline recommends recruitment maneuvers in patients with moderate or severe acute respiratory distress syndrome r19
      • Brief intervals (eg, 40 seconds) of increased airway pressure (eg, 40 cm H₂O) may increase oxygenation; however, there is risk for overdistention and consequent shunting r40
    • Sedation to improve mechanical ventilation tolerance and decrease oxygen requirements r40
    • Neuromuscular blockade for 48 hours early in the course of severe cases improves 90-day mortality and increases the time off the ventilator without increasing muscle weakness r24
  • Specific ventilator protocols
    • In response to a shortage of critical care specialists during pandemic situations, the American Thoracic Society has published a step-by-step tutorial with video to assist nonintensivists with selecting reasonable initial ventilator settingsr44 and a guide to troubleshooting problems in ventilated patients for nonintensivistsr45
    • NIH ARDS Network ventilator protocol r16c100
      • Calculate predicted body weight
        • Males (in kg) = 50 + 2.3 (height, 60 in) r16
        • Females (in kg) = 45.5 + 2.3 (height, 60 in) r16
      • Select any ventilator mode
      • Set ventilator settings to achieve initial tidal volume of 8 mL/kg predicted body weight r16
        • Reduce by 1 mL/kg at intervals of 2 hours or less until tidal volume equals 6 mL/kg predicted body weight r16
      • Set initial rate to approximate baseline minute ventilation (not greater than 35 breaths per minute) r16
      • Adjust tidal volume and respiratory rate to achieve pH and plateau pressure goals
      • Plateau pressure goal is 30 cm H₂O or less r16
        • Check plateau pressure (0.5 second inspiratory pause) at least every 4 hours and after each change in PEEP or tidal volume
        • If plateau pressure is greater than 30 cm H₂O, decrease tidal volume in increments of 1 mL/kg (maintain minimum of 4 mL/kg) r16
        • If plateau pressure is less than 25 cm H₂O and tidal volume is less than 6 mL/kg, increase tidal volume by 1 mL/kg until plateau pressure is greater than 25 cm H₂O or tidal volume equals 6 mL/kg r16
        • If plateau pressure is less than 30 cm H₂O and breath stacking or dyssynchrony occurs, increase tidal volume in 1 mL/kg increments to 7 or 8 mL/kg (if plateau pressure remains less than 30 cm H₂O) r16
      • Oxygenation goal is PaO₂ of 55 to 80 mm Hg or SpO₂ of 88% to 95% r16
        • Use a minimum PEEP of 5 cm H₂O r16
        • Consider use of incremental FiO₂/PEEP combinations to achieve goal using ARDS Network table of combinationsr16
  • Acute respiratory distress syndrome of any severity classification
  • Hypercapnic respiratory acidosis may develop in some patients

Comorbidities c101

  • Usually related to underlying etiology (eg, sepsis, pancreatitis, trauma)


  • Continuously monitor blood pressure, pulse oximetry, temperature, and respiratory rate (from ventilator)
  • Frequently monitor arterial blood gas
  • Central venous pressure monitoring is not mandatory but can assist with fluid management; pulmonary artery catheter is not indicated

Complications and Prognosis


  • Common complications that occur in an ICU setting include the following:
    • Ventilator-induced lung injury, especially pulmonary edema c102c103
    • Ventilator-associated barotrauma (eg, pneumothorax, subcutaneous edema) c104c105c106
    • Ventilator-associated pneumonia r46c107
    • Catheter-related infections c108
    • Poor nutrition and loss of muscle mass c109c110
    • Deep vein thrombosis c111
    • Gastrointestinal bleeding c112
    • Delirium r24c113
  • Pulmonary fibrosis develops in roughly two-thirds of patients with acute respiratory distress syndrome; patient may become increasingly reliant on persistent mechanical ventilation r47c114
  • Cognitive impairment is common (70%-100% at hospital discharge, 46%-80% at 1 year, and 20% at 5 years) r48c115
  • Depression and posttraumatic stress disorder are common r48c116c117


  • No specific biomarker is considered predictive of outcome r39
  • Mortality outside of a clinical trial setting remains high and relatively unchanged since the original consensus definition was developed in 1994 r49
    • Mild acute respiratory distress syndrome is associated with 34.9% mortality r2
    • Moderate disease is associated with 40.3% mortality r2
    • Severe disease is associated with 46.1% mortality r2
    • Highest risk of death is when sepsis is the underlying cause; trauma-related cases have a lower mortality rate than those unrelated to trauma r40

Screening and Prevention

Screening c118

Prevention c119

  • No evidence exists for effective preventive measures specific to this syndrome; however, some good practices likely to decrease risk include: r50
    • Primary prevention of nosocomial pneumonia
    • Primary prevention of aspiration c120
    • Appropriate antibiotic use
    • Restrictive use of blood transfusions
    • Avoid vaping and e-cigarette use r7c121c122d4
      • If continuing e-cigarette use or vaping
        • Do not use devices purchased from sources other than authorized retailers
        • Do not modify devices or use devices modified in any manner not intended by the manufacturer
        • Only use substances sold by an authorized manufacturer
        • Do not use products that contain THC (tetrahydrocannabinol)
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