Restrictive lung disease - ARDS and DAD Flashcards

1
Q

What is ARDS?

A

Acute respiratory distress syndrome

A medical condition occurring in critically ill patients characterized by widespread inflammation in the lungs. ARDS is not a particular disease; rather, it is a clinical phenotype which may be triggered by various pathologies such as trauma, pneumonia and sepsis.

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2
Q

How is ARDS defined?

A
  • Respiratory distress
  • Reduced pulmonary compliance
  • CXR - new bilateral, diffuse, patchy or homogeneous pulmonary infiltrates
  • Gas exchange abnormalities
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3
Q

What are pulmonary causes of ARDS?

A
  • Pneumonia
  • Gastric aspiration
  • Inhalation
  • Injury
  • Vasculitis
  • Contusion
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4
Q

What are non-pulmonary causes of ARDS?

A
  • Shock
  • Septicaemia
  • Haemorrhage
  • Multiple transfusions
  • DIC
  • Pancreatitis
  • Acute liver failure
  • Trauma
  • Head injury
  • Malaria
  • Fat embolism
  • Drugs
  • Eclampsia
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5
Q

What is the pathophysiology of ARDS?

A

Diffuse alveolar damage - occurs in 3 distinct phases

  • Exudation
  • Hyaline membrane formation
  • Fibro-proliferation
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6
Q

What happens in the exudative phase of the pathophysiology of ARDS?

A

Protein rich oedema occurs within the first day following injury. This is rich in fibrin, and is similar to pulmonary oedema.

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7
Q

What happens in the hyaline membrane formation stage of the pathophysiology of ARDS?

A

Hyaline membranes are laid down as a result of exudation. These are composed of necrotic epithelial debris and exuded protein.

They line the alveolar ducts and alveolar membranes as a layer of protein. This stage is accompanied by pulmonary oedema and RBC extravasation. This occurs within 4 or 5 days.

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8
Q

What happens in the fibro-proliferative phase of the pathophysiology of ARDS?

A

This results in the formation of interstitial fibrosis and inflammation. This is the body’s attempt to organise itself, but failing.

This process occurs all over the lungs - it is not specifically confined. Gas exchange becomes inhibited due to the presence of hyaline membrane, fluid accumulation and fibrosis.

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9
Q

What are clinical features of ARDS?

A
  • Central Cyanosis/hypoxameia
  • Tachypnoea
  • Tachycardia
  • Bilateral fine inspiratory crackles
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10
Q

What investigations would you do in someone with suspected ARDS?

A
  • Bloods - FBC, U+E’s, LFTs, amylase, clotting, CRP, BCs, ABG
  • CXR
  • Pulmonary artery catheter
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11
Q

What are the diagnostic criteria for the diagnosis of ARDS?

A
  • Acute onset
  • CXR - bilateral infiltrates
  • PCWP < 19mmHg or a lack of CCF
  • Refractory hypoxaemia
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