ARDS + Respiratory failure

Question 1

ARDS pathogenesis

Answer 1

increase in Inflammatory mediators → ↑ capillary permeability and pulmonary oedema

Question 2

Clinical features of ARDS

Answer 2

Tachypnoea
Bilateral fine creps - with the absence of CCF

3 cardinal features:

• new infiltrates on CXR
• Hypercapnia - decompensated respiratory failure
• Cyanosis

Question 3

Investigations of ARDS

Answer 3

Respiratory examination 
Basic obs
Bloods: FBC, U+E, LFTs, clotting, CRP,
ABG
CXR: bilateral perihilar infiltrates

Question 4

Diagnosis of ARDS

Answer 4

Acute onset
CXR shows bilateral infiltrates
No evidence of congestive cardiac failure
Respiratory failure

Question 5

Mx of ARDS

Answer 5

Admit to ITU for organ support and Tx underlying cause

• Ventilation
• Treat underlying cause
• Sepsis - sepsis 6

Question 6

Causes of ARDS

Answer 6

Pulmonary:
Pneumonia
Aspiration
Covid 19

Systemic: 
Shock
Sepsis
Trauma
Haemorrhage 
Acute liver failure
DIC
Acute pancreatitis

Question 7

Exudate

Answer 7

Protein rich

Due to infection or malignancy causing increased capillary permeability

Question 8

CPAP

Answer 8

Continuous positive airway pressure

Question 9

Type 1 resp failure

Answer 9

Hypoxia
Normal/low CO2
V/Q mismatch and diffusion failure

Question 10

Type 2 Resp Failure

Answer 10

Hypoxia
Hypercapnia

Alveolar hypoventilation ± V/Q mismatch

Question 11

Causes of V/Q mismatch

Answer 11

PE
Pulmonary HTN
Asthma (early)
Pneumothorax
Atelectasis

Question 12

Alveolar Hypoventilation

Answer 12

Obstructive:
Late COPD
Late Asthma
Bronchiectasis
Bronchiolitis

Restrictive:
↓ respiratory drive: CNS sedation, trauma
NM disease: cervical cord lesion

Chest: kyphoscoliosis, obesity

Fluid:

• Pulmonary oedema
• Pneumonia
• Infarction

Fibrosis

Question 13

V/Q ratio

Answer 13

0.8

Question 14

Feature of respiratory failure

Answer 14

Acute hypoxia:

• Dyspnoea
• Confusion
• Cyanosis

Chronic hypoxia:

• Polycythaemia
• Cor pulmonale

Hypercapnia:

• Headache
• Flushing and peripheral vasodilatation
• Bounding pulse
• Flap
• Confusion → coma

Question 15

Mx of respiratory failure

Answer 15

Type 1:

• O2 to maintain SpO2 94-98%
• Assisted ventilation if PaO2<8KPa despite 60% O2

Type 2:

• Controlled O2 aiming for SpO2 88-92%
• Check ABG after 20mins

Question 16

Mechanisms of oxygen therapy

Answer 16

Nasal specks
Non rebreathing mask
Venturi mask

Question 17

Criteria for ARDS

Answer 17

Acute onset - within 1 week
Pulmonary oedema without congestive HF
Hypoxaemia