ARDS

Question 1

What is acute respiratory distress syndrome?

Answer 1

Acute lung injury characterised by severe hypoxaemia in the absence of a cariogenic cause.
Inflammatory damage to alveoli leads to pulmonary oedema, respiratory compromise and acute respiratory failure

Question 2

Definition of ARDS?

Answer 2

Acute onset within 7 days
PaO2:FiO2 ratio < 300 (this is the proportion of oxygen in the blood)
Bilateral infiltrates on CXR
Alveolar oedema not explained by fluid overload or cariogenic causes

Mild 200-300 PaO2:FiO2 ratio
Moderate = 100-200
Severe <100

Question 3

What are the causes of acute respiratory distress syndrome

Answer 3

Direct:
Pneumonia
Smoke inhalation
Aspiration
Fat embolus

Indirect:
Sepsis
Acute pancreatitis
Polytrauma

Question 4

Describe the pathophysiological process of ARDS?

Answer 4

Direct injury activates inflammatory response
Breakdown of alveolar-capillary barrier leads to increased permeability and pulmonary oedema
Fluid infiltration impairs ventilation and gas exchange leading to hyperaemia
Damage to type II alveolar cells impairs surfactant production reducing lung compliance and worsening ventilation
Affected alveoli expand more and more with focus from this expansion resulting in trauma and cell damage.

Question 5

What are the clinical features of ARDS?

Answer 5

Worsening dyspnoea in the presence of risk factor or underlying cause
Cyanosis, hypoxia, tachycardia, tachypnoea
Inspiratory crackles on auscultation

Question 6

What investigations for ARDS?

Answer 6

Routine bloods
Blood cultures
ABG
CXR

Question 7

What is seen on CXR?

Answer 7

Diffuse bilateral infiltrates similar to pulmonary oedema

Question 8

What is the management of ARDS?

Answer 8

Supportive treatment with ventilation
Focused treatment fo the underlying cause

Emergency intubation and ITU admission

Question 9

What are the goals of ITU management of ARDS?

Answer 9

Maintaining intravascular volume to ensure adequate tissue perfusion limiting oedema\Lower tidal volumes used in ventilation, reducing shear forces from over distension and ventilator associated injury
Positive and end-expiratory pressure to splint airways and avoid the damage caused by cyclical opening of alveoli

Question 10

What his the prognosis of ARDS?

Answer 10

High mortality (40%) although varies on underlying cause, age,
Survivors can develop pulmonary fibrosis