ARDS

Question 1

What does ARDS stand for?

Answer 1

Acute Respiratory Distress syndrome

Question 2

What is ARDS?

Answer 2

It is an acute, severe inflammary recation of the lungs to pulmonary damage

Question 3

What is the aetiology of ARDS?

Answer 3

Most commonly caused by sepsis

• often in the lung (2nd to pneumonia)

But might also be caused by

• aspiration and inhalation trauma
• acute pancreatitis
• trauma
• burns
• transfusion-related lung injury
• pulmonary contusion (bruise of lung)
• DIC
• drug overdose
• COVID-19 pneumonia

Question 4

What are risk factors for developin ARDS?

Answer 4

• Sepsis
  
  • pneumonia
  • pancreatitis
• Trauma
• Aspiration
• Blood transfusions
• Drowingin
• Burns/smoke inhalatio
• Cigarette smoke
• Lung transplants
• Hx of C2 missuse

Question 5

What happens during ARDS?

Answer 5

1. Difuuse alveolar damage –> Damage to alveolar membrane –> inflammatory change –> pulmonary oedema –> impaired gas exchange

Might lead to

1. Early phase
   
   1. hypoxemic resp failure with increased alveolar- aterial oxygen gradient + poorly compliant lungs
2. Clearing or fibroproliferative phase
   
   1. causing lung fibrosis

Question 6

What are clinical symptoms of ARDS?

Answer 6

Based on clinicl criteria

• Dypnoe
• Maybe fever + cough
• possible pleuritic chest pain

Question 7

What are the presenting sign on examination of ARDS?

Answer 7

• Tachycardia and Tachypneu
• Cyanosis
• Diffuse coarse crackels on ausculation
• fever, cough, pleuritic chest pain
• Often in critically ill patients

Question 8

What are the clinial criterial for diganosisng ARDS?

Answer 8

1. Symptom onset within <1 Week of suspected insult
2. Bilaterial diffuse opacities on Chest X-Ray
3. Symptoms are not fully explained by Congestive HF
4. PaO2 : FiO2 < 300mmHg

Question 9

Which investigations would you do in a patient with suspected ARDS?

Answer 9

1. Chest X-Ray
   
   1. bilateral pulmonary infiltrates
2. ABG
   
   1. hypoxaemic resp. failure (might progress to hypercapnic resp failure)
3. Try to find cause
   
   1. identify triggers
      
      1. e.g. Lipase for Acute pancreatitis,
      2. FBC: neutrophils for sepsis
   2. rule out differentials (expecially Heart failure (BNP)), D-dimer, Troponin

Question 10

What is the epidemiology of ARDS?

Answer 10

• 10-15 % of ICU patients meet criteria
• 64 cases per 100.000
• With 30-50% mortality

Question 11

How does tissue damage (intra or extra-pulmonary) can lead to ARDS?

Answer 11

Release of inflammatory Mediators –> Attraction of Neutrophils into alveoli –> Excessive release of inflammatory mediators (e.g. cytokines, proteases) –> Damage to endothelial cells and alveolar capillaries –> Diffuse alveolar Damage (DAD –> also damge to tight junctions that prevent fluid from enterin air space)

Question 12

What does inflammatory damage to endothelial and alveolar capillary cells in ARDS lead to?

Answer 12

1. Oedema (non-cariogenic)
2. Hypoxaemai
   
   1. compensation with hyperventilation leading to resp alkalosis
3. Shunting

Might later lead to interstitial fibrosis