Respiratory physiology - Chemoreceptors - Lung disease Flashcards
What can happen to PaCO2 levels in chronic lung disease?
Chronically elevated
What happens to the sensitivity of central chemoreceptors in chronic lung disease?
Desensitised due to contract chronic levels of CO2
What do desensitised chronic lung disease individuals rely on?
Peripheral receptors
What do peripheral chemoreceptors detect?
Change in PO2 and H+ conc
What is hypoxic drive?
Rather than ring driven by hypercapnea (decreased PO2) but are driven by hypoxia (decreases PO2)
Where are the peripheral chemorectrs found?
In the periphery, in the carotid and aortic bodies
Where is the [H+] detected in peripheral chemoreceptors?
Systemic Plasma
When is a reflex stimulation of ventilation triggered?
When there is a significant fall in PO2 in arterial blood
What is a significant fall in PO2?
UNDER 60mmHg (haemoglobin dissociation curve)
When the PO2 falls below 60mmHg, what is th effect on the station of haemoglobin by oxygen?
Small changes in the po2 now have a great effect on the percent O2 bound to have haemoglobin
What PO2, will the peripheral chemoreceptors kick into action - ventilation?
Below 60mmHg
Around 3000m
What needs a greater decrease in partial pressure to increase ventilation, PO2 or PCO2?
O2
Need to be below 60mmHg
Exponential rise in ventilation
Are peripheral receptors responding to arterial PO2 or total oxygen content?
Only arterial
Not the po2 bound to haemoglobin
What will happen to respiration rate in an anaemic patient with normal lung function, who has a blood oxygen content half the normal value?
It will stay the same
As the peripheral chemoR respond to arterial PO2 and not total.
The plasma PO2 will be normal
When does chronic lung disease become important clinically?
administering sedative agents or anaesthetic agents
How do gaseous anaesthetic agents effect respiration rate and tidal volume?
increase respiration rate and decrease tidal volume
What is the main determinant of alveolar ventilation?
tidal volume
Anaesthetic decreases tidal volume, how does this effect alveolar ventilation?
decrease
What drugs depress respiratory centres?
barbiturates and opioids
Why do overdose on opioids result in death?
as a result of respiratory failure.
decrease sensitivity to pH and therefore response to PCO2.
Also, decrease peripheral chemoreceptors to decrease PO2
Do the opioids decrease sensitivity of peripheral chemoreceptors?
yes, decrease response to PCO2
What is the effect of nitrous oxide on peripheral chemoreceptors?
blunts the peripheral chemoR to falling PaO2
Does nitrous oxide have an effect in the central chemoR?
no, only peripheral
does not monitor PaCO2 in the blood
How does nitrous oxide effect individuals with chronic lug disease?
individuals on hypoxic drive
desensitised to CO2
you Knockout the peripheral chemoR response, due to NO
they cant regulate their blood gas composition
What are the blood gas compositions in an induvial with chronuic lung disease and taking NO?
PCO2 INCREASES
PO2 decreases
Why does administering O2 to an individual with chronic lung disease and taking NO? `
tells the body that O2 levels are fine when they are not.
CO2 levels are not ok and you cannot get rid of CO2
O2 will stop them leaving and further decrease PO2
What else do the peripheral chemoR respond to?
increasing plasma [H+]
