Ventilation and perfusion Flashcards
Respiratory function- what do lungs need to function
Lungs require adequate ventilation of alveoli and adequate blood supply to exchange and transport oxygen and carbon dioxide
What is ventilation and perfusion matching
For gas exchange to occur ventilation and perfusion need to be in the same place at the same time
This is,,,
- ventilation and perfusion matching
- perfect ratio 1/1
Regions of lungs
Dependant (lower regions of the lung) are better ventilated because alveoli in the non dependant (upper regions) are already inflated because of weight of the hanging lung
What is ventilation
Ventilation is the movement of air in and out of the lungs
Perfusion
Blood flow in the capillary beds
Regional differences in ventilation
Lower ventilate better than upper as interpleural pressure is less negative at the bottom than the top of the lung
Lower lung has greater potential for increased ventilation
Factors affecting ventilation
Pleural pressure
Altered airway resistance
Lung volume
Use of body position to…
Maximise ventilation.
Maximise diaphragmatic function
Optimise v/q matching
And to decrease WOB and drain sputum
Mechanical ventilation
Positive pressure ventilation reverses ventilation away from the dependent lung because:
•The diaphragm is pushed down passively
•Airflow takes the path of least resistance
TLC (total lung capacity)
Total volume of gas in the lungs after maximum inspiration
Vital capacity
is the volume of gas that can be exhaled after a full inspiration
Residual volume
volume of gas that remains in the lungs after a full expiration
Expiratory reserve volume
extra volume of gas that you can exhale forcefully when you reach a end of expiratory tidal volume
Functional residual capacity
volume of gas remaining at the end of a tidal volume exhalation
Inspiratory reserve volume
extra volume of gas that can be inhaled voluntary at the end of a inspiration tidal volume
Tidal volume
volume of air inhaled and exhaled during one respiratory cycle
What causes variations in lung volume
Body size
Age
Sex
Closing volume
Volume at which alveoli start to collapse
Dead space
is the volume of air that is inhaled but is not used within gas exhchange
Alveolar dead space
air within alveoli that should be involved with gas exchange but there’s a lack of blood supply so it isn’t involved
Physiological dead space
sum of both alveoli and anatomical dead space
Anatomical dead space
gas left in the mouth or trachea when we breath
