History and exam

Key diagnostic factors

common

presence of risk factors

Key risk factors include sepsis, aspiration, severe trauma, pneumonia, pancreatitis, burns and smoke inhalation, blood transfusions, lung transplantation, and a history of alcohol misuse.

low oxygen saturation

Low despite supplemental oxygen.

acute respiratory failure

Progressively worsening respiratory failure in the setting of critical illness.

Other diagnostic factors

common

critically ill patient

Patients developing ARDS are critically ill, often with multi-system organ failure.

dyspnoea

Dyspnoea is the most common presenting symptom.

increased respiratory rate

Respiratory rate >20 breaths per minute.

pulmonary crepitations

Pulmonary crepitations on auscultation are common and typically diffuse.[27]

low lung compliance

Measured by tidal volume/(plateau pressure minus positive end-expiratory pressure).

fever, cough, pleuritic chest pain

These symptoms are often present, particularly if the underlying cause of ARDS is pneumonia.

uncommon

frothy sputum

Presence of cough productive of frothy sputum, or frank pulmonary oedema that may be blood-tinged.

Risk factors

strong

sepsis

Sepsis is the most common underlying cause of ARDS, usually having a pulmonary origin.[4][5] The incidence of ARDS in patients with sepsis is between 6% and 7%, but is significantly higher in patients with septic shock.[8][23][24] Systemic activation of inflammation and coagulation is thought to lead to indirect injury to the alveolar-capillary membrane.

aspiration

Aspiration of gastric contents is a common cause of ARDS.[5] About one third of hospitalised patients with a witnessed aspiration event develop ARDS.[25] Aspiration is thought to cause direct injury to the alveolar epithelium and alveolar-capillary membrane.

pneumonia

Pneumonia from any source (bacterial, viral, fungal, parasitic) is a common cause of ARDS.[4][26][27] Direct injury by the pathogen and the inflammatory response to the pathogen are thought to be the responsible mechanisms.

severe trauma

About 7% to 10% of patients with severe trauma develop ARDS.[28] Potential mechanisms include indirect injury from early haemorrhagic shock or later onset of multiple organ failure. Pulmonary contusions increase the risk of ARDS, as do long bone fractures, aspiration, and multiple transfusions of blood products.

blood transfusions

Multiple transfusions of blood products are associated with ARDS.

Transfusion-related acute lung injury (TRALI) can also develop with transfusion of as little as 1 unit of any plasma-containing blood product. Proposed mechanisms of TRALI include recipient neutrophil activation by donor-antibody recognition of recipient neutrophil epitopes or by biologically active lipids released from stored red blood cells.

lung transplantation

ARDS, also known as primary graft dysfunction, occurs in 10% to 25% of patients after lung transplantation.[29] The mechanism is thought to be due to ischaemia-reperfusion injury.

Risk factors for ARDS (primary graft dysfunction) after lung transplantation include donor smoking, higher FiO₂ in the allograft at reperfusion, use of cardiopulmonary bypass, recipient body mass index, and pulmonary arterial hypertension in the donor or recipient.

pancreatitis

Although not well studied, ARDS probably occurs in 10% to 20% of patients with severe acute pancreatitis.[30] In one study, treatment of patients with acute pancreatitis with octreotide reduced the incidence of ARDS.[31]

history of alcohol misuse

Alcohol misuse is associated with an increased incidence of ARDS in adults.[8][9]

The mechanism is thought to be due to depletion of endogenous antioxidants.

burns and smoke inhalation

ARDS is common after burns and smoke inhalation, with an incidence of 40% among mechanically ventilated patients with burns in one study.[32]

drowning

ARDS is common after significant drowning episodes (grades 3 to 6).[27][33] These patients usually recover much faster than those with other causes of ARDS.[34]

e-cigarette and vaping product use

Emerging in the US in the summer of 2019, an outbreak of e-cigarette and vaping product-associated lung injury was reported among mostly young adults with a history of vaping, presenting with a clinical syndrome identical to ARDS.[35]

Many cases seem to occur in patients vaping tetrahydrocannabinol products that contain vitamin E acetate.[36]

Immunotherapy

A variety of drug exposures have been associated with development of ARDS including various chemotherapies and immunotherapies. Among these, checkpoint inhibitors have emerged as a new cause of ARDS.[37]

weak

drug overdose

Overdose of many common drugs (e.g., salicylates, tricyclic antidepressants, opioids, cocaine, phenothiazines) can cause ARDS, although loss of consciousness with aspiration of gastric contents may also contribute in this setting.[38]

cigarette smoking

Smoking has been associated with an increased risk of ARDS in the setting of severe trauma, sepsis, transfusion, and after lung transplantation.[10]​[39][40][41]

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