Critical care

Question 1

Acute Respiratory Distress Syndrome
- Pathophysiology

Answer 1

1) Increase permeability of alveolo-capillary membrane –> inflammatory oedema
2) Increased non-aerated lung tissue –> higher lung elastance (lower compliance)
3) Increased dead space –> hypoxemia & hypercapnia

Question 2

Acute Respiratory Distress Syndrome
- Epi

Answer 2

• 10% of ICU admission
• 23% ventilated pts
• Mortality 45% in severe category
• Susceptible to ventilator-induced lung injury (VILI) –> lung protective strategies to reduce total stress (transpulmonary pressure) and strain (ratio between tidal volume and functional residual capacity)

Question 3

What are the lung protective strategies to prevent ventilator-induced lung injury (VILI) and its complication?

Answer 3

Lung Protective Ventilation
1) Lower tidal volume (4-8ml/kg) & plateau pressure ≤30cmH2O
2) Use of PEEP (moderate level) and lung recruitment maneuvers to reduce non-aerated lung
3) Ventilation in prone position (≥16h) – increases lung homogeneity, improve VQ ratio, reduce stress & strain, decrease VILI

Potential complication from Lung Protective Ventilation:
- Hypercapnea due to alveolar hypovent
- Permissive hypercapnea: PaCO2 is allowed to rise and pH to drop. This is to prevent VILI

Question 4

What is the definition of ARDS?

Sources:
2023 European Society of Intensive Care Medicine (ESICM) guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies
and
American Journal of Resp & Crit Care Medicine (AJRCCM) Articles in Press. Published July 24, 2023

Answer 4

= acute diffuse, inflammatory lung injury

• precipitated by risk factors:
  Pneumonia
  Non-pulmonary infection
  Trauma
  Transfusion
  Burn
  Aspiration
  Shock
• clinical hallmarks:
• Hypoxemia
• Diffuse radiographic opacities
• Increased shunting
• increased dead space
• Decreased lung compliance

Question 5

What is the ARDS criteria?

Sources:
2023 European Society of Intensive Care Medicine (ESICM) guidelines on acute respiratory distress syndrome: definition, phenotyping and respiratory support strategies
and
AJRCCM Articles in Press. Published July 24, 2023

Answer 5

General criteria:

1) Risk factors: not exclusively attributable to CCF/ fluid overload, precipitated by pneumonia, other non-pulm infection, trauma, transfusion, aspiration, shock

2) Timing: within 1 week of precipitating factor

3) Chest imaging: Bilat opacities, or B-lines

Criteria specific to ARDS categories: non-intubated, intubated & resource-variable setting

a) Non-intubated:
PFR ≤300mmHg,
or
SpO2/FiO2 ≤315 (if SpO2 ≤97%),
ON
HFNO with flow ≥30L/min,
or
NIV/CPAP with ≥5cmH2O expiratory pressure

b) Intubated:
Mild: PFR >200-300 or SpO2/FiO2 235-315
Moderate: PFR >100-200 or SpO2 149-235
Severe: PFR ≤100 or SpO2/FiO2 ≤148

Resource-variable settings:
SpO2/FiO2 ≤315
- no PEEP or min flow rate of O2 are required for Dx

Question 6

Management of pt in critical care setting

Answer 6

FASTHUGSBID

Feeding/fluid (aim negative or even balance)
Analgesia
Sedation
Thromboprophylaxis
Head up position
Ulcer prophylaxis
Glycemic control
Spontaneous breathing trial
Bowel care
Indwelling catheter removal
Deescalation of Abx

Question 7

Index scoring to predict failure of HFNO or NIV

Answer 7

ROX index: predicts failure of HFNO
HACOR index: predicts failure of NIV

Question 8

ARDSnet protocol

Answer 8