ICU - ARDS Flashcards
What is the Berlin Definition of Acute Respiratory Distress Syndrome (ARDS)?
The Berlin Definition classifies ARDS based on:
timing - within 1 week of a known insult chest imaging - bilateral opacities or lobar collapse
origin of oedema - non-cardiogenic
Hypoxaemia - P:F ratio (PEEP ≥ 5) ≤ 300mmHg
Mild: P:F ratio ≤ 300 and >200mmHg
Moderate: PF ratio ≤ 200 mmHg and > 100mmHg
Severe: PF ratio ≤ 100 mmHg
List common direct (pulmonary) causes of ARDS.
Common direct causes include pneumonia, aspiration of gastric contents, pulmonary contusion, inhalational injury, and near-drowning.
What are typical indirect (extrapulmonary) causes of ARDS?
Indirect causes encompass sepsis, severe trauma, multiple transfusions, pancreatitis, and drug overdose.
Describe the pathophysiological phases of ARDS.
ARDS progresses through three phases:
Exudative Phase: Alveolar epithelial damage, increased permeability, pulmonary oedema.
Proliferative Phase: Proliferation of type II pneumocytes and fibroblasts, resolution of oedema.
Fibrotic Phase: Fibrosis and lung remodeling, leading to decreased lung compliance.
What is the cornerstone of mechanical ventilation strategy in ARDS management?
Low tidal volume ventilation (6 mL/kg predicted body weight) to minimize ventilator-induced lung injury.
How does positive end-expiratory pressure (PEEP) benefit ARDS patients?
PEEP helps prevent alveolar collapse, improves oxygenation, and reduces shunting.
When is prone positioning indicated in ARDS?
Prone positioning is recommended for patients with severe ARDS (PaO₂/FiO₂ ≤ 150 mmHg) to improve oxygenation and reduce mortality.
What role do neuromuscular blocking agents (NMBAs) play in ARDS management?
Early administration of NMBAs may improve oxygenation and reduce ventilator dyssynchrony in severe ARDS.
Why is fluid management important in ARDS, and what strategy is preferred?
Conservative fluid management is preferred to reduce pulmonary oedema and improve lung function without compromising other organ perfusion.
What is the approximate mortality rate for severe ARDS?
The mortality rate for severe ARDS is approximately 45%.
What ventilator settings should be used to implement lung protective ventilation in ARDS?
Tidal volume of 6 mL/kg predicted body weight, plateau pressure <30 cm H₂O, and permissive hypercapnia if necessary.
What is driving pressure and why is it important in ARDS?
Driving pressure = Plateau pressure – PEEP. Reflects lung stress; keeping it <15 cm H₂O is associated with improved survival.
What is the rationale for using permissive hypercapnia in ARDS?
Allows reduced tidal volumes and prevents volutrauma; must monitor for acidosis-related complications.
Describe the use and benefits of recruitment maneuvers in ARDS.
Recruitment maneuvers temporarily increase airway pressures to open collapsed alveoli; may improve oxygenation but can cause barotrauma or hypotension.
Under what circumstances should ECMO be considered in ARDS?
In severe ARDS with refractory hypoxaemia (PaO₂/FiO₂ <80 despite optimal ventilation), especially in experienced centers.
What complications are associated with mechanical ventilation in ARDS?
Barotrauma, volutrauma, atelectrauma, ventilator-associated pneumonia, ventilator-induced diaphragmatic dysfunction.
How is ARDS differentiated from cardiogenic pulmonary oedema?
ARDS has normal left atrial pressure, bilateral infiltrates not explained by cardiac failure, and a non-cardiac cause.
What radiological features are typical of ARDS?
Bilateral diffuse alveolar infiltrates/opacities on chest X-ray or CT scan without cardiomegaly or pleural effusions.
How does ARDS affect respiratory system compliance?
It significantly reduces compliance due to alveolar collapse, oedema, and fibrosis, resulting in stiff lungs.
What non-ventilatory therapies may have a role in ARDS?
Conservative fluid strategy, prone positioning, NMBAs, corticosteroids (selected cases), and ECMO in severe cases.
What are the three most common causes of ARDS?
The three most common causes of ARDS are pneumonia, sepsis, and aspiration of gastric contents.
