Acute respiratory distress

Question 1

Define

Answer 1

syndrome of acute and persistent lung inflammation with increased vascular permeability. Characterised by:

• Acute onset
• Bilateral infiltrates consistent with pulmonary oedema
• Hypoxaemia
• No clinical evidence of increased left arterial pressure (pulmonary capillary wedge pressure)
• ARDS is the severe end of the spectrum of acute lung injury

Question 2

Causes

Answer 2

Severe insults to the lungs and other organs leads to the release of inflammatory mediators

These lead to increased capillary permeability, pulmonary oedema, impaired gas exchange and reduced lung compliance

Causes

• Sepsis
• Aspiration
• Pneumonia
• Pancreatitis
• Trauma/burns
• Transfusion
• Transplantation (bone marrow and lung)
• Drug overdose/reaction

There are THREE pathological stages of ARDS:

• Exudative
• Proliferative
• Fibrotic

Question 3

Epidemiology

Answer 3

Annual UK incidence: 1/6000

Question 4

Symptoms

Answer 4

Rapid deterioration of respiratory function

Dyspnoea

Respiratory distress

Cough

Symptoms of CAUSE

Question 5

Signs

Answer 5

Cyanosis

Tachypnoea

Tachycardia

Widespread inspiratory crepitations

Hypoxia refractory to oxygen treatment

Signs are usually bilateral but may be asymmetrical in early stages

Question 6

Management

Answer 6

CXR - bilateral alveolar infiltrates and interstitial shadowing

• Bloods - to figure out what the cause is
• FBC
• U&Es
• LFT
• ESR/CRP
• Amylase
• ABG

Blood culture

Sputum culture

• NOTE: plasma BNP < 100 pg/mL could distinguish ARDS from heart failure

Echocardiography

• Check for severe aortic or mitral valve dysfunction
• Low left ventricular ejection fractions = haemodynamic oedema rather than ARDS

Pulmonary Artery Catheterisation

• Check pulmonary capillary wedge pressure (PCWP)

Bronchoscopy

• If the cause cannot be determined from the history