Condition- ARDS

Question 1

Define ARDS

Answer 1

Acute Respiratory Distress Syndrome

A syndrome of acute non-cardiogenic pulmonary oedema with diffuse lung inflammation caused by direct injury or systemic illness

Question 2

Desrcibe how ARDS develops

Answer 2

1. Direct lung injury/ systemic illness
2. lung damamge
3. release of inflammatory mediators
4. increased capillary permeability
5. fluid leakage in alveoli (–> necrosis + fibrosis)
6. reduced surfactant production
7. Impaired gas exchange and reduced lung compliance

Question 3

What is the most common risk factor for ARDS?

Answer 3

Septicaemia

Question 4

Name some risk factors/ causes of ARDS

Answer 4

Pulmonary:

• Pneumonia
• Gastric aspiration
• Smoke inhalation
• Pulmonary contusion
• Vasculitis

Other:

• Septicaemia
• Haemorrhagic Shock
• Multiple transfusions
• Lung transplant
• Pancreatitis
• Drowning
• DIC
• Acute liver failure
• Trauma
• Drugs/ Toxins

Question 5

What percentage of people admitted to ITU meet the criteria for ARDS? and what factor makes this percentage higher?

Answer 5

10-15%

If patients are on mechanical ventilation

Question 6

What are the presenting symptoms of ARDS?

Answer 6

• SOB
• resp distress
• cough + frothy sputum

Question 7

What are the sighs of ARDS on physical examination?

Answer 7

• Cyanosis
• Dyspneoa and Tachyopnea
• Tachycardia
• Pleuritic pain
• Bilateral widespread fine inspiratory crackles (diffuse rales)
  
  • May be asymmetrical in early stages
• Peripheral Vasodilation
• Hypoxic respiratory failure requiring high levels of oxygen

Question 8

What are the three main diagnostic criteria for ARDS?

Answer 8

1. Acute onset (<1week)
2. CXR: bilateral infiltrates (represents pulmonary oedema)
3. Resp failure. Refractory hypoxaemia (resistant to O2 treatment) with PaO2:FiO2 <300 on PEEP

(+ 4. Pulmonary capillary wedge pressure <19mmHg or lack of clinical congestive heart failure. PCWP is an indirect measure of the left atrial pressure)

1. Alternative cause (cardiogenic pulmonary oedema)
2. Rapid onset i.e <1 week
3. Dyspnoea, cough, frothy sputum
4. Similar on CXR

Question 9

Which investigations would you conduct to identify ARDS? and what would be the positive results?

Answer 9

1. Chest X-ray: bilateral infiltrates
2. Bloods, ABG (PF ratio)
3. Echo: aortic or mitral valve dysfunction
4. Pulmonary artery catheterisation: PCWP<18mmHg (dif HF)

Question 10

What is a key feature of ARDS on a CXR?

Answer 10

BAT WING OPACITIES

Question 11

what might be seen on a CXR of someone with pulmonary oedema?

Answer 11

Similar as pulmonary oedema

• A - alveolar oedema (bat wing opacities)
• B - Kerley B lines.
• C - cardiomegaly.
• D - dilated upper lobe vessels.
• E - pleural effusion

Question 12

How would you differentiate between bilateral pneumonia and ARDS?

Answer 12

• Fever and cough without sputum
• Do not have severe hypoxaemia so PaO2: FiO2 is not <300

Question 13

What can be seen on this CXR and what couldve caused this?

Answer 13

Question 14

Which type of resp failure does ARDS cause and why?

Answer 14

Type 1 resp failure (hypoxaemia) = failure of oxygenation