Ventilation Flashcards
What is anatomical dead space ?
Volume of gas occupied by the conducting airways and this gas is not available for exchange- 150ml
What is pulmonary (minute) ventilation ?
total air movement into/out of lungs
What is alveolar ventilation ?
Fresh air getting to alveoli and therefore available for gas exchange
How is total pulmonary ventilation calculated ?
TPV= TV X RR
How is air to alveoli calculated ?
Tidal - dead space
How is alveolar ventilation calculated ?
AV= ait to alveoli X RR
Will tidal volume be lower or higher when someone is anxious ?
Lower but respiratory rate increases
Will tidal volume be lower or higher when someone is chilled out and relaxing ?
Higher but respiratory rate decreases
What is the main factor that affects the alveolar ventilation ?
The depth of the breath, rather than the respiratory rate, because of the influence of the dead space volume
What is hyperventilation ?
Increased ventilation - concerns depth and not frequency of breathing
Relaxed is hyperventilating
What is hypoventilation ?
Decreased ventilation - concerns depth and not frequency of breathing
anxious is hypoventilation
What is partial pressure ?
Pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture
for example if:
Atmospheric pressure = 760mmHg
Pressure of air we breath therefore= 760mmHg
21% of air we breath= O2
What is the partial pressure of air we breath in ?
= 21% X 760mmHg
= 160mmHg
Once air is in alveoli what is it in equilibrium with ?
in equilibrium with the gas that’s in the blood
How is air diluted ?
By dead space, residual volume and adding water vapour
Is partial pressure of O2 in alveoli higher or lower than partial pressure of O2 in the air we breath ?
Lower
As air is diluted
What is atmospheric pressure ?
760mmHg (101kPa)
What is normal alveolar ventilation ?
4.2L/min
What is the fluctuation of PO2 and PCO2 like under normal resting conditions ?
PO2 and PCO2 remain fairly constant
What happens to PO2 and PCO2 during hyper-ventilation (increased alveolar ventilation) ?
PO2 rises to about 120 mm Hg and PCO2 falls to about 20 mmHg
What happens to PO2 and PCO2 during hypo-ventilation (decreased alveolar ventilation) ?
PO2 falls to 30mmHg and PCO2 rises to 100mmHg
What is normal alveolar partial pressure ( systemic arterial PP) of O2 ?
100mmHg (13.3kPa)
What is normal alveolar pressure (systemic arterial PP) of CO2 ?
40mmHg (5.3kPa)
Which part of the lung changes more significantly in volume when the pressure increases ?
The base, the volume change is much greater for a given change in pressure
What is the relationship between height from base to apex and alveolar ventilation?
Alveolar ventilation declines with height from base to apex
When is compliance lower ?
At the apex due to being more inflated at FRC, at the base the lungs are slightly compressed by the diaphragm hence more compliant on inspiration
