Pathophysiology of Respiratory Failure Flashcards
definition of COPD
airflow limitation, irreversible, progressive and associated with inflammatory response of the lungs to noxious particles or gases
3 pathological symptoms that make up COPD
mucous hypersecretion
emphysema
small airway inflammation
3 compartment model of the lungs
Dead space= ventilated but not perfused V/Q= infinite
ideal= V/Q= 1
Shunt (venous admixture)= V/Q= 0
msot important cause of hypoxaemia, TREATMENT?
V/Q mismatch
100% O2
oxygen levels at high and low V/Q respectively
high V/q –> HIGH o2
LOW v/q –> LOW 02
3 potenial causes of V/Q mismatch
pneumonia
pulmonary embolism
COPD
explain how pumonary embolism can cause hypoxaemia
embolism will block off circulation to one part of the lung:
- the blood must now go to other parts of the lung to be oxygenated (increased perfusion)
- other parts of the lung have increased perfusion (V/Q decreases - hypoxaemia)
complication of worsening disease (COPD)
worsening disease –> unable to undertake compensatory hypervent –> hypercapnoea –> loss of CO2 drive and respiration becomes dependent on O2
dangers of high O2 administration in a V/Q mismatch
hypoxic drive is abolished
- increased CO2
- acidosis
effcts of respiratory acidosis
reduced cardiac and resp muscle contractility
reduced endurance time
increased cerebral blood flow
arrythmias
what are the 5 causes of hypoxaemia
reduced PiO2
hypoventilation
V/Q mismatch
Diffusion
R-L shunt
R-L common or uncommon?
uncommon- bit more common in babies
what is a R-L shunt?
blood from the right side of the heart mixing directly into the leftside –> venous admixture
how to distinguish between VQ mismatch and RL shunt?
VQ- responds to 100% inspired O2
RL shunt - does not respond to 100% inspired O2
what are the 2 main causes of hypercapnia
hypoventilation
V/Q mismatch
