14 Cardiovascular - Respiratory Interactions

Question 1

What are the mechanical respiratory influences on the heart?

Answer 1

in inspiration:
increased venous return to RV
increased left EDV and SV

Question 2

What happens to HR when you breathe in and out?

Answer 2

in - increases

out - decreases

Question 3

What are the 2 main mehcanisms accounting respiratory sinus arrhythma

Answer 3

CNS mechanisms

Reflex response

Question 4

What are the principles of the CNS mechanisms?

Answer 4

inspiratory motor neurones:
increase inspiratory muscle activity
send inhibitory signal to NA, increasing HR

Question 5

What are the principles of the reflex response?

Answer 5

pulmonary stretch receptors go to NTS, inhibiting NA

this reduces Vagal tone, increasing HR

Question 6

What chemoreceptor groups are associated with the reflex effects in systemic hypoxia?

Answer 6

carotid bodies

aortic bodies

Question 7

What is hypoxia?

Answer 7

a fall in PaO2 below 60mmHg (8.1 kPa)

Question 8

What is the effect of hypoxia if respiration cannot increase?

Answer 8

primary cardiovascular reflex
decreased HR and vasoconstriction

02 CONSERVING

Question 9

What is the effect of hypoxia if respiration can increase?

Answer 9

increased respiratory effects on HR dominate, so HR increases

Question 10

Name 5 causes of systemic hypoxia when respiration cannot be increased?

Answer 10

paralysis
high spinal transection
long dive underwater
fetus in utero
severe respiratory disease

Question 11

What are the local effects of hypoxia on the heart?

Answer 11

decreased HR and contractility

Question 12

What are the local effects of hypoxia on the brain?

Answer 12

vasodilation

Question 13

What are the local effects of hypoxia on muscle?

Answer 13

vasodilation

Question 14

What are the local effects of hypoxia on the lungs?

Answer 14

vasoconstriction

Question 15

What is the net effect of local effects of hypoxia

Answer 15

available oxygen is directed to the brain

Question 16

What are the bad effects of hypoxia?

Answer 16

pulmonary vasoconstriction may cause oedema

eventually RV failure

Question 17

What might a patient with respiratory disease look like?

Answer 17

blue bloater

Question 18

Name 3 causes of systemic hypoxia where respiration can increase

Answer 18

hypoxic atmosphere
high altitude
less severe respiratory disease

Question 19

What is the difference when respiration can be increased in hypoxia?

Answer 19

reflex effects of peripheral chemoreceptor stimulation on heart rate are overcome by effects of increased respiration on HR

Question 20

What happens when respiration can increase in hypoxia?

Answer 20

increased respiration
increased HR
general vasoconstrictinoon

Question 21

What does someone who is hypoxic by can increase respiration look like?

Answer 21

pink puffer

Question 22

What stimulates the diving reflex?

Answer 22

cold water stimulation on the face / nose (trigeminal)

Question 23

What does stimulation of the diving reflex cause?

Answer 23

NTS inhibition of central inspiratory neurones

Question 24

What does the diving reflex cause?

Answer 24

expiratory apnoea
decreased HR (increased vagal activity)
vasoconstriction

an O2 conserving reflex

Question 25

What are the clinically significant scenarios for the diving reflex?

Answer 25

sinus washing
irritant vapours
intubation / bronchoscopy. laryngoscopy
lumps of food caught in pharynx
quadriplegics when mucous aspirated

Question 26

how can the diving reflex be fatal?

Answer 26

a strong response can cause expiratory apnoea (cardiac arrest)

Question 27

How can you relieve someone of the effects of the diving reflex?

Answer 27

mouth - mouth ventilation to terminate apnoea and reverse reflex

Question 28

When might the diving reflex be useful clinically?

Answer 28

use an ice bag over the face to stop a supraventricular tachycardia