Respiratory System: Pulmonary Ventilation Flashcards
State definitions for total and alveolar ventilation.
Total ventilation = the volume of air entering/leaving the respiratory system in a given time period.
Alveolar ventilation = the volume of inspired air that reaches alveoli (and thus participates in gas exchange) in a given time period.
Why is pulmonary ventilation important?
Pulmonary ventilation ensures partial pressure gradients are maintained between alveolar air and blood.
This enables good gas exchange to take place in respiring tissues.
Increased ventilation increases the partial pressure gradient between the alveoli and the blood which increases gas exchange.
What is hypo and hyperventilation?
Hypoventilation= excessive levels of CO2within arterial blood (PaCO2>6.0 kPa). Due to insufficient levels of breathing. Hyperventilation= reducedlevels of CO2within arterial blood (PaCO2< 4.9 kPa). Due to excessive levels of breathing
Draw diagrams to demonstrate hyper and hypoventilation
Hyperventilation increases alveolar oxygen pressure and reduces carbon dioxide pressure.
Hypoventilation reduces alveolar oxygen pressure and increases carbon dioxide pressure.
What is tidal volume, vital capacity and functional residual capacity?
Tidal volume = volume of normal breath (quiet breathing)
Vital capacity = max volume inspired upon forced inspiration
Functional residual capacity = The maximum volume of air that the lungs can hold
. It’s residual volume + expiratory reserve volume
What is the difference between residual, inspiratory reserve and expiratory reserve volume?
Residual volume = residual volume of air after forced expiration
Inspiratory reserve volume = difference between peak of tidal inspiration and max inspiration
Expiratory reserve volume = volume left in lungs after quiet expiration
Give the equations for total and alveolar ventilation.
Why are the equations for total and alveolar ventilation different?
Total ventilation does not inc ‘dead-space’ in the airways. And a residual volume of air is left in the lungs as alveoli don’t completely collapse. So alveoli have a mix of ‘stale’ and ‘fresh’ air
Also, the resp system is 2 way, so the final ≈150mL air of dead-space never reaches the alveoli or takes part in gas exchange, bc it is first to leave the at the beginning of the next expiration.
Describe how the respiratory system moves air between the atmosphere and alveoli. Draw a diagram
Air moves from high to low pressure. Therefore pressure changes within the lungs are induced via volume changes to transport air:
Describe the process of inspiration
Describe expiration
Describe the function of the pleural cavity in respiration.
The pleural cavity (aka pleural space) is the sealed, fluid filled space lining the chest wall and each lung.
Function: resist changes in volume.
Also removes friction produced by the lungs rubbing on the chest wall as they inflate/deflate.
The opposing recoil of the lungs (inwards) and chest wall (outwards) means intrapleural pa is sub-atmospheric.
What is a pneumothorax caused by?
A pneumothorax is presence of air within the pleural space.
Occurs if either pleural membrane is damaged, which results in a passageway for air to enter (either from the atmosphere or lungs).
Describe what happens during a pneumothorax
As intrapleural Pa< atm Pa, air enters the pleural space.
This increases the volume of the pleural space at the expense of the lungs. This causes atelectasis.
Elastic lung recoil and thoracic cavity expansion during breathing cause air to enter the pleural space, further reducing lung volume.
Fortunately each lung is surrounded by a separate pleural space, so only 1 lung may be affected, the individual can keep breathing (though laboured).
