Drive - gas exchange Flashcards
What is meant by the term “dead space”?
The volume of air in the lungs not contributing to ventilation
Approximately what is the total dead space in the lungs?
175mls
Where does gas exchange occur?
Between the alveoli and capillaries
What are the 7 histological layers that O2 in the alveoli must pass through?
Alveolar epithelium Tissue interstitium Capillary endothelium Plasma layer Red cell membrane Red cell cytoplasm Haemoglobin binding
What is ventilation perfusion matching?
The correct proportion of alveolar airflow (ventilation and capillary blood flow (perfusion) available to each alveolus
What is the main effect of ventilation-perfusion inequality?
The partial pressure of oxygen is decreased in systemic-arterial blood
What is the possible cause of (extra) dead space/wasted ventilation?
A blood clot
What is the possible cause of cause of a shunt?
Alveolar collapse
What does a decrease in the partial pressure of O2 in the alveoli and nearby blood result in?
Vasoconstriction (why diverts blood away)
What causes vasoconstriction in the lungs?
Hypoxic pulmonary constriction
What cause bronchoconstriction?
a local decrease in the partial pressure of CO2
What does PaCO2 stand for?
Arterial CO2
What does PACO2 stand for?
Alveolar CO2
What does PaO2 stand for?
Arterial O2
What does PAO2 stand for?
Alveolar O2
What does PIO2 stand for?
Pressure of inspired O2
What does VA stand for?
Alveolar ventilation
What does VCO2 stand for?
CO2 production
How many oxygen molecules can a fully saturated haemoglobin molecule contain?
4
What changes in temperature and pH causes the oxygen-dissociation curve to shift right?
Increase temperature
Decrease pH (more acidic)
What changes in temperature and pH causes the oxygen-dissociation curve to shift left?
Decrease temperature
Increase pH (more alkaline)
What effect does CO have on the oxygen-dissociation curve?
Shifts left
What is the normal pH of the blood?
pH = 7.4
What does hypoventilation result in (and why)?
Respiratory acidosis
as there is inadequate ventilation of the alveoli, so PaCO2 increases resulting in more carbonic acid being produced.
What does hyperventilation result in (and why)?
Respiratory alkalosis
as there is excessive ventilation of the alveoli, so PaCO2 decreases resulting in less carbonic acid being produced.
What is the Henderson-Hasselbalch Equation?
6.1 + log10( [HCO3-] / [0.03*PCO2] ) = pH
What are HCO3- level regulated by?
The kidneys
