Gas Exchange Flashcards
What is alveolar ventilation
Volume of air exchanged between the atmosphere and alveoli per minute
What is anatomical dead space
Air which remains in airways which is not available for gas exchange
What is the equation for pulmonary ventilation
Pulmonary ventilation (L) = tidal volume (l/breath) x respiratory rate (breath/min) = 6L under resting conditions
Why is alveolar ventilation less than pulmonary vent
Coz presence of anatomical dead space
How do u work out the alveolar ventilation
AV = (tidal volume - anatomical dead space) x RESP rate = 4.2 l/min under resting conditions
How do u increase pulmonary ventilation
During exercise
Both depth - tidal volume and rate of breathing - RESP rate must increase
But due to dead space it is better to increase depth of breathing
What is ventilation perfusion
Transfer of gases between body and atmos deals on
Vent - rate which gas passing though lungs
Perfusion - rate at which blood is passing through lungs
What is alveolar dead space
Ventilated alveoli which are not adequately perf used with blood as dead space
I’m healthy ppl dead space v small a nd not imp
Increases with disease
What does accumulatin of carbon dioxide do to alveolar dead space
Increases perfusion decreases airway resist lading to increase airflow
Increased vent
Put vasodilator
Increases blood flow
What are the four factors influence the rate of gas exchange across alveolar mem
Partial pressure of oxygen and carbon dioxide
Diffusion coeff for oxy and co2
SA of alv mem
Thickness of alv mem
What is Dalton’s law of partial pressure
Total pressure exerted by gaseous mix = sum of partial pressures of each individual component in the gas mix
What does the partial pressure of a gas determine
The pressure gradient for that gas
The partial pressure of a gas is
Pressure that one gas in a mix of gases would exert if it were only gas present in the whole volume occupied by the mix at a given temp
What si the alveolar gas eqn
PAO2 = PiO2 - [PaCO2/0.8]
The air in the RESP tract is
Saturated with water (water vapour)
What does the water vapour contribute to the pressure
47mmHg to total pressure in lungs
How do we convert to PKa
Convert divide mmHg by 7.5
Across pulmonary caps what Is the pp oxy and co2
Oxy - 60mmHg
Co2 - 6 mmHg
What is the pp oxy and co2 in the systemic caps
Oxy - >60 mmHg
Co2 - > 6 mmHg
Is co2 or O2 more sol in mems
Co2
What is the solubility of gas in membranes known as
Diffusion coefficient
Diff coeff of co2 20X > than that of O2
What does a big gradient between PAO2 and PaO2 mean
Indicate problems with gas exchange in the lungs or a right to left shunt in the heart
What is Ficks law of diffusion
Amount of gas that moves across sheet of tissue in unit time is proportional to the area of the sheet but inversely proportional to its thickness
What increases the SA of the lungs
Alveoli
What are alveoli
Thin walled inflatable sacs Function in gas exchange Walls consist of type 1 alveolar cells Pulmonary caps encircle each alveolus Narrow interstitial space
What are some nonresp functions of the RESP syst
Route for water loss Heat elim Helps maintain normal acid-base balance Enable speech Defend ag inhaled forgein matter Removes various materials Nose serves as organ of smell
What is pulmonary respiration
Volume of air breathed in and out per min
