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Module 103: The Heart, Lungs and Blood > Theme 4: Lecture 6 - Principles of oxygen therapy and sleep apnoea > Flashcards

Theme 4: Lecture 6 - Principles of oxygen therapy and sleep apnoea Flashcards

1
Q

What are the sources of oxygen

A
  • Oxygen Cylinders
  • Wall Supply
  • Oxygen Concentrators
  • Liquid Oxygen
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2
Q

Describe oxygen cylinders

A
  • Widely available (home & institutional)
  • Various sizes
  • Limited length of supply
  • Suitable for limited/short duration treatment
  • Relatively expensive
  • Supply 100% oxygen
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3
Q

Describe oxygen wall supply

A
  • In hospital only
  • Central supply piped into clinical areas
  • May not be available in all clinical areas (clinic rooms)
  • Supply 100% oxygen
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4
Q

Describe oxygen concentrators

A
  • Mains operated machine
  • Molecular sieve- removes nitrogen
  • Oxygen predominant gas >90% concentration
  • Use in the home or when out
  • They don’t run out as they concentrate oxygen from the environment
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5
Q

Describe liquid oxygen

A
  • More highly compressed
  • Larger gaseous volume per cylinder volume
  • Allow higher flow rates
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6
Q

Patient interfaces for oxygen delivery for spontaneously breathing patients

A
  • Nasal cannulae
  • Uncontrolled masks
  • Controlled masks
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7
Q

Name 2 uncontrolled oxygen masks

A
  • Hudson

- Non rebreathe

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8
Q

Name a controlled oxygen mask

A

Venturi mask

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9
Q

FiO2 meaning

A

Fraction of inspired oxygen

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10
Q

Describe nasal cannulae

A
  • Usually well tolerated
  • Accepts flow rates 1-4L/min
  • Delivers 24-40% O2 (= FiO2 of 0.24-0.4)
  • % delivered depends on multiple factors
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11
Q

When are nasal cannulae used

A

In mild hypoxaemia, mot critically ill

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12
Q

Describe a hudson mask

A
  • Simple face mask
  • Delivers 30-60% O2
  • Flow rate 5-10L/min
  • Mixing of O2, room air & exhaled air in mask
  • Don’t know the exact % of O2 patient is getting
  • Used less often
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13
Q

Describe a non rebreathe mask

A
  • Delivers 85-90% oxygen with 15L flow rate.
  • Bag: one-way valve stops: mixing with room air and patient rebreathing expired air
  • Don’t know the exact % of O2 patient is getting
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14
Q

When are non rebreathe masks used

A

-In acutely unwell patients (step down as soon as possible)

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15
Q

Describe a venturi mask

A
  • Controlled Oxygen

- Venturi valve allows delivery of a fixed concentration of oxygen

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16
Q

What is oxygen the treatment for

A

Hypoxaemia (not breathlessness)

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17
Q

What are the clinical indications to give oxygen

A
  • Acutely hypoxaemic patients
  • Chronically hypoxaemic COPD patients with acute exacerbation
  • Chronically hypoxaemic COPD patients who are stable
  • Palliative use in advanced malignancy (Sats <90% and breathless, though often multifactorial)
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18
Q

Target oxygen saturation for a normal young adult

A

96-98%

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19
Q

Target oxygen saturation for a normal adult > 70 yrs

A

94-98%

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20
Q

Target oxygen saturation for patients at risk of hypercapnic respiratory failure (ie patients with COPD)

A

88-92%

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21
Q

What may be the causes of acute breathlessness with hypoxaemia in a patient without significant background lung problems

A
  • acute pulmonary oedema
  • acute pneumonia (inclduign Covid-19)
  • acute pneumothorax
  • acute asthma
  • (critical illness: major trauma/MI/sepsis/CO poisoning)
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22
Q

What may acute hypoxaemia cause

A

Acute cardiac dysrhythmia and organ failure

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23
Q

What is the oxygen treatment for acute breathlessness with hypoxaemia in a patient without significant background lung problems

A
  • Maximal oxygen treatment.
  • High flow uncontrolled mask- first line
  • Alter flow and delivery device when stable
  • Target SpO2 = 94-98%
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24
Q

What is the other treatment, excluding oxygen therapy, for acute breathlessness with hypoxaemia in a patient without significant background lung problems

A
  • Secure and maintain airway patency
  • Enhance circulation (volume, anaemia, cardiac output)
  • Avoid/reverse respiratory depressants
  • Establish reason for hypoxaemia and treat
    e. g. bronchospasm (in asthma), pulmonary oedema (in left ventricular failure).
  • If not improving, may need ventilation (Invasive or non-invasive)
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25
Which patients are at risk of hypercapnia if they are given high dose oxygen
- Chronic hypoxic lung disease (COPD, Bronchiectasis / Cystic fibrosis) - Chest wall disease (Kyphoscoliosis, Thoracoplasty) - Neuromuscular disease - Obesity related hypoventilation
26
Why shouldn't you give too much oxygen to chronically hypoxaemic patients
-These patients will often tolerate a lower PaO2 than normal so adjusted to chronic hypoxaemia -They often rely on their hypoxaemic drive -If you over-correct their pO2 you may switch off their respiratory drive This could lead to, further CO2 retention, worsening acidosis, narcosis (reduced level of consciousness) and death -You can kill the patient with oxygen
27
Treatment for chronically hypoxaemic patients with COPD who have an acute exacerbation
- To maintain modest oxygenation whilst preventing CO2 retention & acidosis - Deliver oxygen by fixed percentage venturi oxygen masks starting at 24% (controlled oxygen therapy) - Target saturations 88-92%
28
How do you assess response to treatment
With arterial blood gases
29
What treatment may chronically hypoxaemic patients with COPD who have an acute exacerbation need if they aren't improving
Non-invasive ventilation
30
What may untreated chronically hypoxaemic patients develop
- Pulmonary hypertension - Right ventricular hypertrophy - Right ventricular failure (cor pulmonale) - Secondary polycythaemia (raised haemoglobin)
31
Which patients may be given long term oxygen treatment (LTOT)
``` COPD patients with pO2 < 7.3 kPa or COPD patients with pO2 7.3 < 8 kPa AND: -secondary polycythaemia -nocturnal hypoxaemia -peripheral oedema/evidence of right ventricular failure -evidence of pulmonary hypertension ```
32
Describe long term oxygen treatment (LTOT)
- Provided from an oxygen concentrator | - O2 treatment by more than 15 hrs a day
33
Benefits of long term oxygen treatment (LTOT) (7)
- Improved long term survival - Prevention of deterioration in pulmonary hypertension - Reduction of polycythaemia (raised Hb) - Improved sleep quality - Increased renal blood flow - Reduction in cardiac arrhythmias - Improved quality of life
34
Advantages of portable oxygen
- May improve breathlessness in some patients | - May extend duration of LTOT
35
Disadvantages of portable oxygen
- Most patient's breathlessness is not due to low pO2 - Weight of cylinders - Duration of supply
36
Definition of apnoea
“Cessation of Airflow” for 10 seconds or longer
37
Causes of apnoea
- Central: Respiratory Control Centre - no respiratory effort - Obstructive: collapse of pharyngeal airway during sleep (continuation of respiratory effort)
38
Definition of obstructive sleep apnoea
5 or more obstructive apnoeas per hour
39
Definition of hypopnoea
reduction in airflow by 50% accompanied by desaturation of 4% and/or arousal from sleep
40
Why is the prevalence of sleep apnoea increasing
Due to increasing rates of obesity
41
Risk factors for sleep apnoea (obstructive sleep apnoea/hypopnoea syndrome OSAHS) (9)
- Male sex - Obesity - Neck circumference greater than 43 cm (41cm women) - Family history of OSAHS - Smoking - Alcohol/sedative use - Craniofacial abnormalities (e.g retrognathia) - Pharyngeal abnormalities (e.g. tonsillar enlargement) - Some medical conditions (hypothryroidism, acromegaly, pregnancy) - Sleeping supine
42
Name the regions of the pharynx
- Nasopharynx - Oropharynx - Laryngopharynx
43
What happens in sleep apnoea
- Sleep - Relaxation of muscles/tissues surrounding pharyngeal airway - Collapse and obstruction of the airway - snoring - Apnoea - Arousal - Muscle tone returns - airway clears - Resumption of breathing - Sleep
44
Clinical features of sleep apnoea (7)
- Snoring (Hx often from partner) - Nocturnal choking/waking with a “start” - Unrefreshing/restless sleep - Morning dry mouth - Morning headaches - Excessive daytime sleepiness (Difficulty concentrating, Irritability/Mood changes, Sleeping at inappropriate times) - Nocturia
45
Nocturia
Getting up at night because you have to pass urine
46
Complications of sleep apnoea
- Cor pulmonale (Right heart failure 2ndry respiratory disease) - Secondary Polycythaemia (Excess of red blood cells)
47
Definition of obstructive sleep apnoea/hypopnoea syndrome (OSAHS)
Repetitive apnoeas and symptoms of sleep fragmentation with excessive daytime sleepiness
48
Investigations for sleep apnoea
- Epworth Sleepiness Scale | - Sleep Studies eg Nocturnal oximetry, Video studies, Polysomnography
49
What is polysomnography
- Also called a sleep study, is a comprehensive test used to diagnose sleep disorders. - Polysomnography records your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements during the study
50
How is sleep apnoea diagnosed
- Using the apnoea/hypopnea index | - Or oxygen desaturation index
51
Apnoea/hypopnea index (AHI) equation
AHI = (apnoeas + hypopnoeas) / total hours of sleep
52
What co morbidities is sleep apnoea associated with (8)
- Increased risk of accidents - Hypertension - Type 2 diabetes - Ischaemic heart disease - Heart failure - Cerebrovascular disease/stroke - Cardiac arrhythmias - Death
53
What are the management goals for sleep apnoea
- Resolve signs and symptoms of OSA - Improve sleep quality - Normalise apnoea-hypopnoea index (AHI) and oxyhaemoglobin saturation levels
54
What can patients do to help with sleep apnoea
- Weight loss - Avoid sleeping supine - Avoid alcohol
55
Describe CPAP
- Continuous Positive Airway Pressure (CPAP) - Device generates airflow => positive pressure delivered to airway via mask - Intraluminal pharyngeal pressure > surrounding pressure - Pharynx stays open
56
When is CPAP used to treat sleep apnoea
- Patients with mild OSAHS AND additional co-morbidities - Patient with mild OSAHS and high risk profession (e.g. bus driver) - Patients with moderate/severe OSAHS regardless of symptoms - But not patients with mild OSAHS, no additional risk factors who aren’t excessive sleepy
57
Benefits of CPAP
- Symptoms resolve - ↓ apnoea/hypopnoea - ↓ daytime sleepiness - ↓ risk road accidents - ↑ quality of life - Normalises BP
58
Problems with CPAP
- Adherence an issue - Airway drying/irritation (Can humidify) - Mask problems (Air leak, Comfort) - Normally life long treatment
59
Treatment options for sleep apnoea
- Mandibular advancement devices - CPAP - Surgery
60
How do mandibular advancement devices work to treat sleep apnoea
They hold soft tissues of the oropharynx forward

Module 103: The Heart, Lungs and Blood (51 decks)

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