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Flashcards in Control of Ventilation Deck (18)
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1
Q

What part of brains is involved in subconscious ventilation

A

Pons

Medulla

2
Q

What nerves

A
Phrenic = diaphragm
Intercostal = external intercostal
3
Q

What part of medulla set breathing pattern

A

DRG - control muscles of inspiration through phrenic and intercostal, receive sensory from vagus

VRG - control muscles of larynx / pharynx

PRG - receive sensory info from DRG, speak with higher brain to initiate and terminate inspiration

4
Q

How do you change respiratory drive

A
Emotion via limbic
Voluntary 
Mechano-sensory
Swalloing inhibits 
Drugs 
Chemical composition detected by chemoreceptors
5
Q

What is the primary stimulus for changes in ventilation

A

CO2
Detected by central chemoreceptors in medulla
More sensitive to small changes in PCo2

6
Q

How do central chemoreceptors work

A

Detect changes in H+ in CSF which are related to CO2

7
Q

What happens when there is an increase in CO2

A

Rate and depth of breathing increases to remove CO2

8
Q

Where are peripheral receptors located

A

Carotid and aortic bodies

9
Q

What do peripheral receptors detect

A

Change in arterial Po2 NOT CONTENT

Relatively insensitive and require a significant fall in Po2 or rise in H

10
Q

Can you override peripheral

A
No
Effects are instantaneous 
Increased RR and TV 
Blood flow directed to kidney and brain 
INceased CO
11
Q

When are peripheral chemoreceptor important

A

If chronic elevation of PCO2
Central response is blunted
Patients go into hypoxic drive and rely on peripheral receptors to detect O2 falling

12
Q

Why do you have to be careful in patients who rely on peripheral

A

Careful when giving O2 to patients with chronic lung disease e.g. COPD
They will have elevated PCO2
Rely only on O2 levels for their breathing

13
Q

What does hypoventilation cause

A

Increased CO2
Blood = acidic
COPD / neuro / chest wall

14
Q

What does hyperventilation cause

A

Decreased CO2 and alkaline blood
Decreases free Ca = paraesthesia / cramps
Anxiety / HF / PE

15
Q

What drugs affect ventilation

A

Opiods / barbiturates = depress
Anasthetic = increase RR but decrease TV
NO = blunts peripheral chemo so if chronic lung = no way to control ventilation

16
Q

What happens at altitude

A

Peripheral detect fall in O2 = hyperventilation
Resulting hypocapnia and alkalosis stop any increase in RR due to central chemoreceptors
After a few days kidney works to remove alkalosis so peripheral takes over again
Rise in DPG
Polycythaemia - physiological as erythropoietin produced from kidney but can cause hypervisocotyi

17
Q

If an anaemic patient has o2 content 1/2 normal what happens to RR + depth

A

No change
Receptors respond to partial pressure
Amount of O2 in plasma is normal but just decreased RBC to hold O2 so content reduced
Haem saturation will be the same

18
Q

What is more uncomfortable
1- a high PCo2 and low Po2
2- a low o2 and no CO2

A

1

PACO2 increased and impairs the gradient so will stay in blood