Respiratory: Gas Exchange Flashcards
What is pulmonary ventilation?
The volume of air breathed in and out per minute
What is alveolar ventilation?
The volume of air exhnace between the atmospher and the alveoli per minute
Why is alveolar ventilation less than pulmonary ventilation
Due to the presence of anatomical dead space
What is the volume of anatomical dead space?
150ml
What is meant be the term ‘dead space’
the gas is not available for gas exchange
Which area of the lung is generally better ventilated?
The bottom (slight)
What area of the lung is generally better perfused?
Bottom
What is alveolar dead space?
Alveoli which are well ventilated but poorly perfused
What is the physiological dead space?
Alveolar dead space + anatomical dead space
What can increase alveolar dead space?
Disease
What happens if there is an accumulation of CO2 in the alveoli?
This indicates increased perfusion.
This results in a decrease in airway resistance and thus an increase in airflow.
What hapens if there is an increase in alveolar O2/
this indicated that this area of the lung is well ventilated
Vasodilation will now occur to direct blood flow to the well ventilated area
What happens if there is a decreased CO2 in the alveoli
this indicated poorly perfused lung tissue
Airway resistance will thus increase to limit airflow to that area
What happens if there is an decrease on oxygen
this indicates poor ventilation
Vasocontriction will occur to direct blood away from this area
What four factors influence the rate of gas exchange?
Partial pressure gradient
Diffusion Coefficient
Surface Area
Thickness of the alveolar membrane
What is Daltons law of partial pressures?
Total pressure exerted by a gaseous mixture= sum of the partial pressures of each of the individula components
What is the partial pressure of a gas?
The pressure that one gas in a mixture would exert if it were the only gas present in the whole volume occupied by the mixture
What is the alveolar gas equation
PAO2= PiO2- [PaCO2/0.8]
What is atmospheric pressure?
760
What is the water pressure in the lungs
47
What is the pressure of inspired air
713
What is the partial pressure of inspired oxygen
150
What is the partial pressure of carbon dioxide in the capillaries
40
What is the partial pressure of oxygen in alveolar air
100
