Physiology 3 Flashcards
What is anatomical dead space?
The volume of inspired air that remains in the conducting airways where it cannot be involved in gas exchange (it is expired unchanged)
What does pulmonary ventilation (L/min) =?
Tidal volume (L/breath) X respiratory rate (breath/min)
Why is alveolar ventilation?
The volume of air that is going to exchange gases with the blood
Approximately how much of the airway is dead-space?
150ml
What is the equation for alveolar ventilation?
(Tidal volume - dead space) X respiratory rate
What 2 types of dead space can you get?
Anatomical/ airway dead space (air left in airways which doesn’t reach alveoli and therefore doesn’t take part in gas exchange)Alveolar dead space (alveoli not perfused)
What is pulmonary ventilation?
The volume of air breathed in and out per minute
What 2 things can be done to incase pulmonary ventilation e.g. during exercise?What way is more advantageous?
Increase depth (tidal volume)Increase breathing rateIncreasing depth of breathing (due to dead space)
What does the transfer of gases between the body and atmosphere depend upon?
Ventilation (rate at which gas is passing through the lungs)Perfusion (rate at which blood is passing through the lungs)
What is the V/Q ration?
Measurement used to assess the efficiency and adequacy of the matching of two variables: “V” – ventilation – the air that reaches the alveoli. “Q” – perfusion – the blood that reaches the alveoli.
V/Q ratio at the bottom of the lungs?
Less than 1 (higher blood supply)
V/Q ratio at the top of the lungs?
more than 1 (higher ventilation)
How well does ventilation and perfusion in the lung normally match?
Not exactly the same but usually does matter except sometimes in disease (where the alveolar dead space could increase significantly)
What is alveolar dead space?
Ventilated alveoli which are not adequately perfused with blood
What is the physiological dead space?
Anatomical dead space + alveolar dead space
What normal happens regarding ventilation perfusion match in the lungs?
Local controls act on the smooth muscles of airways and arterioles to match airflow to blood flow
What does the accumulation of CO2 in the alveoli cause?
Due to increased perfusion = decreases airway resistance leading to increased airflow
What does an increase in alveolar O2 conc. lead to?
Due to increased ventilation therefore causes pulmonary vasodilation increasing blood flow to match larger airflow