Acute Respiratory Failure

Question 1

in hypoxemic resp failure the arterial partial pressure of O2 (PaO2) is below…

Answer 1

8kPa (60mmHg)

WHEN PT IS BREATHING ROOM AIR

Question 2

hypercapnic resp failure is when the arterial partial pressure of CO2 (PaCO2) is

Answer 2

> 6.7 kPa (50mmHg)

Question 3

name a compensatory mechanism for shunting

Answer 3

• pulmonary hypoxic vasoconstriction in response to poor oxygenation diverts perfusion towards well ventilated alveoli
• this is only able to compensate a little bit

Question 4

6 causes of hypoventilation

Answer 4

• resp centre depression
  
  • drugs, anaesthesia head injury, encephalopathy
• neurololgical
  
  • spinal cord injury, myasethenia gravis, GBS,
• musculuar
  
  • myopathy, fatigue, dystrophy, malnutrition
• chest wall abnormalities
  
  • ank spon, pleural fibrosis, kyphosis
• airway obstruction
• decreased lung compliance
  
  • high intra-abdominal pressure

Question 5

causes of ventilation perfusion mismatch

Answer 5

• intrapulmonary physiological shunting
  
  • pulmonary oedema, atelectasis, pneumonia
• intracardiac anatomical shunting L -> R
  
  • tetralogy of fallot, eisenmenger’s syndrome

Question 6

causes of alveolar diffusion abnormality

Answer 6

• severe destructive disease
  
  • fibrosis, ARDS
• severe pulmonary oedema

Question 7

causes of resp failure that take minutes

Answer 7

PTX
PE
Pulmonary oedema
Anaphylaxis

Question 8

Causes of respiratory failure that takes hours

Answer 8

Asthma
Pneumonia
Pulmonary oedma
Metabolic acidosis

Question 9

Causes of respiratory failure that takes days-weeks

Answer 9

Pleural effusion
Exacerbation of COPD
Pneumonia