Sleep Apnoea and Respiratory Failure

Question 1

What happens on inspiration?

Answer 1

• rib cage moves up and out
• intercostal muscles contract
• diaphragm contracts and moves down
• pressure in lungs decreases so less than outside and air rushes in

Question 2

What happens on expiration?

Answer 2

• intercostal muscles relax
• diaphragm relaxes and moves up
• elastic recoil of lungs forces them to contract
• pressure inside lungs greater than outside so air gets pushed out

Question 3

What are the peripheral chemoreceptors?

Answer 3

• carotid and aortic bodies

Question 4

Hypoxic pulmonary vasoconstriction

Answer 4

• if alveolus has no oxygen supply = hypoxic

- vasoconstriction occurs = no perfusion = no more oxygen = won’t be inflated

Question 5

Type 1 respiratory failure

Answer 5

• PaO2 <8 kPa

Question 6

Type 2 respiratory failure

Answer 6

PaO2<8kPa AND PaCO2 >6.5kPa

Question 7

Mechanisms of hypoxia

Answer 7

• hypoventilation
• diffusion abnormality
• ventilation/perfusion mismatch
• right to left cardiac shunt bypassing lungs
• low inspired oxygen = high altitude/air flight

Question 8

Example of ventilation perfusion mismatch

Answer 8

Lobar pneumonia
Asthma = mucus plugs so obstructs airflow
Lobar collapse
PE
Pneumothorax

Question 9

Example of diffusion abnormality

Answer 9

Sarcoidosis
Pulmonary fibrosis
COPD

Question 10

Example of hypoventilation

Answer 10

Kyphoscoliosis
Thoracoplasty for TB
COPD
Motor Neurone Disease
Muscular Dystrophy
Morbid obesity

Question 11

Example of right to left shunt

Answer 11

Eisenmenger syndrome

Question 12

Types of Resp Failure

Answer 12

Acute and chronic for type 1 and 2

Question 13

LTOT

Answer 13

• improves survival for COPD with hypoxia
• reduces hypoxia complications = polycythaemia, cor pulmonale
• at least 15 hours per day

Question 14

Define COPD with hypoxia

Answer 14

PaO2<7.3kPa

Question 15

Chronic Type 1 Resp Failure Consequences

Answer 15

• Pulmonary hypertension
• Cor pulmonale = peripheral oedema
• 2ndry polycythaemia = stroke
• symptoms from ischaemic heart/peripheral vascular diseases
• poor sleep/fatigue

Question 16

CPAP

Answer 16

= continuous positive airway pressure

• pushes pressure into airways mainly during exp
• expands collapsed portions of lungs which are under ventilated
• improves hypoxia and V/Q mismatch
• keeps airways open in sleep apnoea
• doesn’t overcome hypoventilation

Question 17

Cause of type 2 resp failure

Answer 17

ventilation failure

Question 18

Treatment of acute type 2 resp failure

Answer 18

• oxygen therapy
• 0.5 to 2l/min via nasal cannulae
• 24%-28% masks using venture valves
• keep sats 88-92%
• monitor Co2 levels via ABG regularly
• consider nn invasive ventilation if Ph and Co2 not improving

Question 19

Causes of hypoventilation

Answer 19

• airways obstruction = COPD< severe asthma
• hyper expanded lungs = COPD
• thoracic cage problems = kypho, thoacoplasty, obesity
• weakness of resp muscles = MND, musc dystrophy

Question 20

Non invasive ventilation

Answer 20

• improves hypoventilation
• delivers high pressure during insp
• improves oxygenation
• reduces/prevents hypercapnia
• useful in conditions causing hypoventilation and Type 2 resp failure

Question 21

When to use Non invasive ventilation

Answer 21

• acute type 2 in hospital (COPD exacerbations)

- chronic type 2 at home

Question 22

Define obstructive sleep apnoea?

Answer 22

• repetitive episodes of partial or complete upper airway obstruction during sleep

Question 23

Where is the problem anatomically in sleep apnoea?

Answer 23

• between soft palate and tongue base

Question 24

How to diagnose sleep apnoea?

Answer 24

• home sleep study

Question 25

Define apnoea?

Answer 25

complete cessation of airflow for at least 10 seconds

Question 26

Define hypopnoea?

Answer 26

Reduction in airflow to under 50% or by 30% for at least 10 seconds - with desaturation of at least 4%

Question 27

Apnoea and Hypopnoea Index

Answer 27

number of apnoeas and hypopnoeas per hour of study

Question 28

How to measure severity of sleep apnoe

Answer 28

Apnoea and hypopnoea index

Question 29

RDI

Answer 29

``` Respiratory Disturbance Index 0-5 = normal 5-15 mild OS 15-30 = moderate 30+ severe ```

Question 30

OSA Who?

Answer 30

- 1 in 5 adults - 24% mild and 9% women - increases with age until 65 - most undiagnosed

Question 31

RF of OSA

Answer 31

- obesity! = narrowed airway - BMI>30 - neck circumference >16.5 inches - male = longer pharyngeal airway - Afro-Caribbean - micrognathia - tonsillar hypertrophy

Question 32

Associated conditions with OSA

Answer 32

- micrognathia or retrognathia - large adenoids and tonsils - acromegaly - Downs - Hypothyroid - cushings - T2D - HTN

Question 33

Sleep History

Answer 33

- bed partner/family - heavy snoring - witnessed apnoeas = prod to start breathing - arousals = wake up suddenly with snort - unrefreshed on waking - daytime tiredness - planned and unplanned naps - other CV RF

Question 34

OSA Diagnosis on history how?

Answer 34

Epworth Sleepiness Scale out of 24 >10 abnormal

Question 35

Consequences of OSA

Answer 35

- excessive daytime hypersomnolence - fall asleep at wheel - sustained attention required for cognitive function - 2-3x greater risk of car crash - inform DVLA of diagnosis

Question 36

Medical consequences of OSA

Answer 36

RF for - CV mortality - systemic HTN - T2D - CAD - Stroke - Congestive HF - Pulmonary HTN - cardiac arryhtmias

Question 37

Treatment for OSA

Answer 37

- CPAP - weight loss - avoiding alcohol and sedatives - non supine sleep - tonsillectomy - mandibular advancement splints - palatal surgery - maxillofacial surgery - treat cause

Question 38

Indication for mandibular splints

Answer 38

- for simple snorers or mild/mod OSA | - intolerance of CPAP

Question 39

Indication for CPAP for OSA

Answer 39

- moderate or severe sleep apnoea