Property Of Gases Flashcards
What is Boyle’s law of pressure of gas and how does it apply to respiration ?
Pressure of a gas is inversely proportional to its volume
> when diaphragm and chest wall move and increase volume, pressure in alveoli decrease
>gas move from high to low pressure environment»_space; from atmosphere to alveoli
What is partial pressure in a gas mixture ?
Pressure exerted by a gas equal to the pressure it would exert if it was the only gas present
What is the atmospheric pressure ?
Pressure exerted by weight of air above the earth
Does partial pressure change with attitude ?
Yes because atmospheric pressure is lower due to less air pressing down
Composition of air doesn’t change , same percentage of a smaller pressures smaller
Ie : same volume of air will have less molecules
What does partial pressure of a gas in blood represent ?
Dissolved gas exert pressure in the fluid , at equilibrium rate of gas entering fluid = rate exiting
> > partial pressure in fluid =partial pressure in air
What is the effect of water ‘vapour pressure ‘ on partial pressure of other gases ?
Water molecules move in air until reach equilibrium , when air is saturated with vapour pressure
> > means even if same ratios of each gases in inhaled air ,less space for them , represent same proportion of a smaller total pressure
> > partial pressure of each gas will be lower
In which order does oxygen binding and dissolving in blood occur ?
Gas must dissolve first , then bind to Hb until saturation then establishment of definitive partial pressure (= to alveolar pO2)
What does pO2 measure In the blood ?
Pressure exerted by Dissolved O2 (not bound to Hb )
What is the total blood content of oxygen ?
Dissolved gas + gas which is bound to Hb
How is partial pressure different from amount of dissolved gas ? How is it calculated ?
Partial pressure is the pressure exerted by the gas in the fluid
Amount is the mmol of gas per litre (concentration )
Depends on solubility coef of the gas
Amount of gas dissolved = partial pressure X solubility coef
Why are the partial pressure of gas in the alveoli not equal to the atmospheric ones ?
Mixes with residual air , O2 taken up and Co2 given up by blood
>composition of air different from atmospheric , but remain constant
What is the alveolar pO2 and pCO2 ?
pO2 = 13,3 kPa PCO2 = 5,3kPa
What happens in decompression sickness ?
pO2 and pN2 are higher at deep in sea because pressure below sea is higher
> more nitrogen moves from high pressure to low (blood)
»if return quickly to surface , doesn’t give enough time for nitrogen to return to lungs and leave the blood to reequilibrate
»>can form bubble in blood
