Respiratory Failure - Causes & Complications Flashcards
What happens to airways that cause hypoventilation due to airway obstruction due to physical blockade?
-Contraction of smooth muscle
-Excess mucus secretion
-Oedema/swelling
What are some causes of hyperventilation due to problems with initiation of mechanics of breathing?
- Drug overdose(typically opioids)
- Neuromuscular disease(muscular dystrophy, motor neuron disease)
- Stroke
- Issues with lung mechanics(COPD, pulmonary fibrosis, NRDS, pneumothorax)
What is rate of diffusion proportional to?
Rate of diffusion proportianl to surface area/distance^2 x (PA-PC)
What is surface area impacted by in the rate of diffusion?
-Reduced surface area (emphysema)
What impacts distance in the rate of diffusion?
- ↑ basement membrane thickness
(fibrosis) - ↑ thickness of fluid layer/oedema
(pulmonary oedema, pneumonia) - Alveolar injury (ARDS)
What creates the dead space effect?
Reduced perfusion of lung regions, causes an increase in V/Q ratio
What causes the dead space effect?
- Heart failure(cardiac arrest)
- Blocked vessels(pulmonary embolism)
- Loss/damage to capillaries(emphysema)
What creates the shunt effect?
Reduced ventilation or limited diffusion causes a decrease in V/Q ratio
What causes the shunt effect?
Pneumonia, atelectasis, respiratory disease syndrome
What causes anaemia?
- Iron deficiency (decrease in production)
- Haemorrhage(increase in loss)
What happens in carbon monoxide poisoning?
CO prevents O2-Hb binding
What level of PaO2 defines respiratory failure when breathing air at sea level?
‘Respiratory failure’ ≈ PaO2 < 8kPa when breathing air at sea level
What causes type 1 resp failure?
↓ oxygenation
(altitude, VQ mismatch,
pneumonia)
What are the values for PAO2, PaO2, PaCO2 and pH like in type 1 resp failure?
PAO2-Normal
PaO2-Decrease
PaCO2-Normal
pH-Normal
What are the causes of type 2 resp failure?
↓ ventilation
(asthma, COPD, NMD,
drug overdose, apnoea)
