Acute Respiratory Distress Syndrome

Question 1

Define Acute Respiratory Distress Syndrome (ARDS)

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

Explain the aetiology/risk factors of ARDS

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
       o Sepsis	
       o Aspiration	
       o Pneumonia	
       o Pancreatitis	
       o Trauma/burns
       o Transfusion	
       o Transplantation (bone	marrow and	lung)	
       o Drug overdose/reaction	
• There are THREE pathological stages	of ARDS:
       o Exudative	
       o Proliferative	
       o Fibrotic

Question 3

What is the epidemiology of ARDS?

Answer 3

Incidence - 1/600 a yr

Question 4

What are the presenting Symptoms of ARDS?

Answer 4

• Rapid deterioration of respiratory function
• Dyspnoea
• Respiratory distress
• Cough
• Symptoms of its cause

Question 5

What are the Signs of ARDS?

Answer 5

• Cyanosis
• Tachypnoea
• Tachycardia
• Widespread inspiratory crepitations
• Hypoxia refractory O2 therapy
• Signs are usually bilateral but may be asymetrical in early stages

Question 6

What are the Investigations for ARDS?

Answer 6

CXR
- bilateral alveolar infiltrates and interstitial shadowing
Bloods
- FBC, U&Es, FLTs, ESR/CRP, Amylase, ABG, Blood culture (note: plasma BNP<100pg/ml could distinguish ARDS from HF)
Echocardiography
- check for severe aortic or mitral valve dysfunction
- low left ventricular ejection fractions = haemodynamic oedema rather than ARDS
Pulmonary Artery Catheterisation
- check pulmonary wedge pressure (PCWP)
Bronchoscopy
- if the cause cannot be determined from the history