Respiratory Physiology 3 Flashcards
Define ‘pulmonary ventilation’
Total air movement into/out of lungs
Define ‘Alveolar ventilation’
Volume of fresh air getting to alveoli and therefore available for gas exchange
How would you calculate alveolar ventilation?
((tidal volume) - (dead space)) x respiratory rate
What is the typical total tidal volume per min
4.2L
Describe hypoventilation
Breathing real fast
Describe hyperventilation
Breathing real slow
Describe the typical value of anatomical dead space in the respiratory system
150ml
Define ‘dead space’
Dead space is air from alveoli which was not fully exhaled as the prerequisite dead air was exhaled in its place making breathing only ever 70% effective
Describe the composition of air
79% nitrogen
21% oxygen
tiny bit CO2 which we ourselves make
What gas is the brain most sensitive to in terms of respiration?
Carbon dioxide
Describe the impact dead space has on alveolar ventilation
It limits the amount of fresh air getting to the alveoli, reducing gas exchange
Define ‘daltons law’
The total pressure of a gas mixture is the sum of the pressures of the individual gasses
Why is the partial pressure of oxygen in alveoli < in air
- Dead space in air gets sucked down into alveoli and residual volume which dilutes down the air we breathe in
- Air becomes saturated by water vapour in the lungs
- Pressure of gas in equilibrium with pressure of gas in blood
Is there more compliance at the front or the back of the lung?
More compliance at the back than at the front of the lung
What are the changes in alveolar ventilation with height from base to apex?
It declines due to changes in compliance
What is the normal alveolar partial pressure and therefore systemic arterial partial pressure of oxygen?
100mmHg = 13.3kPa
What is the normal alveolar partial pressure and therefore systemic arterial pressure of carbon dioxide?
40mmHg = 5.3kPa
Pulmonary artery carries _________ blood ____ from heart to the lungs
Deoxygenated blood away from the heart to the lungs
Pulmonary vein carries __________ blood _____ the heart from the lungs
Oxygenated blood towards the heart from the lungs
Pulmonary circulation is only concered with?
Gas exchange
Pulmonary circulation is described as what type of system in relation to flow and pressure
High flow low pressure system
What is the typical pressure within the pulmonary circulation?
25/10 mmHg
What does a ‘A’ represent
Alveolar
What does ‘a’ represent
Arterial
what does ‘v’ represent
Venous mixed blood (eg in pul artery)
What dopes PaO2 represent?
Partial pressure of oxygen in arterial blood
What does PACO2 represent
Partial pressure of carbon dioxide in alveolar air
What are the typical pressure values of PAO2 and PaO2
100mmHg and 13.3kPa