Respiratory Failure Flashcards
What is type 1 respiratory failure?
Low pO2
Normal or low pCO2
What is type 2 respiratory failure?
Low pO2
High pCO2
What can cause type 1 respiratory failure?
PE
RDS
Pneumonia
What can cause type 2 respiratory failure?
Asthma
COPD
Obesity
What can cause hypoxia?
Low inspired pO2 Hypoventilation V/Q mismatch Diffusion defect Right to left shunt
What is hypoventilation?
When entire lung is poorly ventilated
What is the effect of hypoventilation?
Alveolar pO2 falls -> arterial pO2 falls -> hypoxaemia
Alveolar pCO2 rises -> arterial pCO2 rises -> hypercapnia
What type of resp failure is caused by hypoventilation?
Type 2
Hypoventilation always causes hypercapnia
What causes acute hypoventilation?
Opiate overdose
Head injury
Very severe acute asthma
What causes chronic hypoventilation?
Severe COPD
Lung fibrosis
Kyphoscoliosis
What are the effects of hypoxaemia?
Impaired CNS function - confusion, irritability
Cyanosis
Cardiac arrhythmia
Vasoconstriction of pulmonary vessels
What are the compensatory mechanisms of chronic hypoxaemia?
Increased EPO secretion by kidney - increased Hb
Increased 2,3-BPG
What is the effect of chronic vasoconstriction of pulmonary vessels?
Pulmonary hypertension
Right heart failure
Cor pulmonale
What are the effects of hypercapnia?
Respiratory acidosis
Impaired CNS function - drowsiness, condusion
Peripheral vasodilation
Cerebral vasodilation
What is the effect of chronic CO2 retention on central chemoreceptors?
CO2 diffuses into CSF - drops CSF pH - stimulates central chemoreceptors
Low CSF pH corrected by choroid plexus cells
pCO2 in blood still high but central chemoreceptors ‘reset’
