Resp 10 - Control of Breathing (Asleep)

Question 1

What is apnoeic threshold?

Answer 1

Threshold over which CO2 level has to be in order to ensure we breathe

Question 2

Sleep = reversible. Other states are not reversible.

Answer 2

T

Question 3

How is sleep usually measured?

Answer 3

Using EEG

awake = high frequency, low voltage

Question 4

Which two muscles are spared functional paralysis during sleep?

Answer 4

Eye

Diaphragm

Question 5

Every 90 minutes, you get REM sleep. What happens as the night progresses?

Answer 5

Deep sleep decreases and REM sleep increases.

Question 6

What are the 2 ways in which breathing is controlled?

Answer 6

1. Brainstem- reflex/automatic
2. Cortex - voluntary/behavioural

(Emotional control comes from livic system - separate control)

NO CORTICAL CONTROL WHEN ASLEEP

Question 7

In the motor homunculus, where is the area in control of voluntary breathing?

Answer 7

Between the shoulder and trunk regions.

Question 8

What is the name of the cluster of respiratory nuclei?

in the brainstem

Answer 8

Pre-Botzinger complex.

Found near/on rostral-ventral-lateral medullary surface

Question 9

Less input from respiratory centres so less output to respiratory muscles during sleep. What is the result of this?

Answer 9

Blood gases change

Question 10

What are the changes in ventilation during sleep?

Answer 10

Minute ventilation decreases by about 10%.

Shallower breathing as well (350ml vs 500ml)

Question 11

What happens to oxygen saturation during sleep?

Answer 11

It stays the same.

Question 12

BREATHING WHEN AWAKE IS DRIVEN BY CO2 LEVELS MORE THAN O2 LEVELS

Answer 12

T

Question 13

ODC means that O2 levels don’t change much during sleep. How come?

Answer 13

You can change breathing. So change partial pressure of O2, but no change in O2 saturation, because most normal people live on flat part of ODC.

Therefore, only a slight drop in SO2 and PO2

Question 14

CO2 INCREASES DURING SLEEP.

Answer 14

T

Question 15

Chemosensitivity to CO2 decreases when you go to sleep. What does this mean?

Answer 15

There must be higher CO2 levels in order to trigger breathing.

Question 16

Why do we become less sensitive to CO2 when we sleep?

Answer 16

Less cortical input going to respiratory centres, meaning we allow our CO2 levels to rise.

(helps keep our brain in the sleeping state)

Question 17

Hypercapnia is mandatory for breathing during sleep. Why?

Answer 17

If you stop CO2 from exceeding apnoeic threshold, they stop breathing.

This condition = Central Sleep Apnoea/Congenital Central Hypoventilation Syndrome (CCHS) - they must be artificially ventilated

Question 18

Where do cartilage rings start?

Answer 18

At the larynx

Question 19

What happens to patients with obstructive sleep apnoea?

Answer 19

The uvula comes in and blocks airway - no airflow.

Question 20

Difference between central sleep apnoea and obstructive sleep apnoea?

Answer 20

Central sleep apnoea = chemosensitivity (rarer)

Obstructive sleep apnoea = mechanics, uvula blocks airflow

Question 21

COPD decreases blood gases, so on steep part of ODC. What does this mean?

Answer 21

Lower O2 saturation which is dangerous at night when sleeping. (Respiratory failure)

Question 22

How can heart failure affect breathing?

Answer 22

Pulmonary oedema can be caused. This exacerbates hyperventilation (more CO2 out), which means you may stop breathing at night.