Respiratory physiology Flashcards
How is ventilation controlled
Central Chemoreceptors, located in the medulla on the brain side of the BBB and peripheral chemoreceptors
What stimulates Central chemoreceptors
CO2 and H+ions
What stimulates peripheral chemoreceptos
Carotid and aortic bodies by increase in paCO2 , arterial H ions and a decrease in PaO2
what are the afferent neurons of peripheral chemoreceptors
cranial 9 and 10
What is tidal Volume
Amount of air that enters or leaves the lung in a single respiratory cycle at rest(~500ml or 6-8ml/kg
What is inspiratory reserve volume
Additional amount of air that can be inhaled after a normal tidal inspiration
What is Expiratory reserve volume
Additional volume that can be expired after a passive expiration
What is residual volume
amount of air in the lung after a maximal expiration
What is functional residual capacity
Amount of gas in the lungs at the end of a passive expiration
What is inspiratory capacity
maximal volume of gas that can be inspired from FRC
What is vital capacity
maximal volume that can be expired after a maximal inspiration
What is total lung capacity
amount of air in the lung after a maximal inspiration
Why is the FRC so important in Anaesthesia ?
The FRC is of great importance to the anaesthetist because with preoxygenation, the FRC is denitrogenated
Why is preoxygenation important ?
It acts as an O2 reservoir at times of apnoea;e.g at induction of general anaesthesia.
What are the physiologically important reasons of FRC?
O2 buffer
-The air within the FRC acts as an O2 buffer during normal breathing.
O2 continuously diffuses from the alveoli to the pulmonary capillaries.
-Prevention of alveolar collapse
If FRC did not exist (i.e. expiration to RV) alveoli would collapse.
Optimal lung compliance
-Conveniently, lung compliance is at its lowest at FRC.
Pulmonary vascular resistance (PVR) is also at its lowest
What reduces FRC
Position
raised intrabdominal pressure
anaesthesia
decreasing age
lung disease e.g. pulmonary fibrosis, pulmonary oedema
ARDS
FRC is increased by
PEEP
Emphysema
Increased height
change from supine to erect position
Factors that shift the oxyhaemoglobin dissociation curve to the left
decrease in temperature
decreased PaCO2
decreased 2,3BPG
decreased H ions
factors that shift the oxygen dissociation curve to the right
increase in temperature
increase in PCO2
increasesd 2,3BPG
increase Hion
