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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
Q

Which patients are at risk of hypercapnia if they are given high dose oxygen

A
  • Chronic hypoxic lung disease (COPD, Bronchiectasis / Cystic fibrosis)
  • Chest wall disease (Kyphoscoliosis, Thoracoplasty)
  • Neuromuscular disease
  • Obesity related hypoventilation
26
Q

Why shouldn’t you give too much oxygen to chronically hypoxaemic patients

A

-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
Q

Treatment for chronically hypoxaemic patients with COPD who have an acute exacerbation

A
  • 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
Q

How do you assess response to treatment

A

With arterial blood gases

29
Q

What treatment may chronically hypoxaemic patients with COPD who have an acute exacerbation need if they aren’t improving

A

Non-invasive ventilation

30
Q

What may untreated chronically hypoxaemic patients develop

A
  • Pulmonary hypertension
  • Right ventricular hypertrophy
  • Right ventricular failure (cor pulmonale)
  • Secondary polycythaemia (raised haemoglobin)
31
Q

Which patients may be given long term oxygen treatment (LTOT)

A 
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
Q

Describe long term oxygen treatment (LTOT)

A
  • Provided from an oxygen concentrator

- O2 treatment by more than 15 hrs a day

33
Q

Benefits of long term oxygen treatment (LTOT) (7)

A
  • 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
Q

Advantages of portable oxygen

A
  • May improve breathlessness in some patients

- May extend duration of LTOT

35
Q

Disadvantages of portable oxygen

A
  • Most patient’s breathlessness is not due to low pO2
  • Weight of cylinders
  • Duration of supply
36
Q

Definition of apnoea

A

“Cessation of Airflow” for 10 seconds or longer

37
Q

Causes of apnoea

A
  • Central: Respiratory Control Centre - no respiratory effort
  • Obstructive: collapse of pharyngeal airway during sleep (continuation of respiratory effort)
38
Q

Definition of obstructive sleep apnoea

A

5 or more obstructive apnoeas per hour

39
Q

Definition of hypopnoea

A

reduction in airflow by 50% accompanied by desaturation of 4% and/or arousal from sleep

40
Q

Why is the prevalence of sleep apnoea increasing

A

Due to increasing rates of obesity

41
Q

Risk factors for sleep apnoea (obstructive sleep apnoea/hypopnoea syndrome OSAHS) (9)

A
  • 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
Q

Name the regions of the pharynx

A
  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
43
Q

What happens in sleep apnoea

A
  • 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
Q

Clinical features of sleep apnoea (7)

A
  • 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
Q

Nocturia

A

Getting up at night because you have to pass urine

46
Q

Complications of sleep apnoea

A
  • Cor pulmonale (Right heart failure 2ndry respiratory disease)
  • Secondary Polycythaemia (Excess of red blood cells)
47
Q

Definition of obstructive sleep apnoea/hypopnoea syndrome (OSAHS)

A

Repetitive apnoeas and symptoms of sleep fragmentation with excessive daytime sleepiness

48
Q

Investigations for sleep apnoea

A
  • Epworth Sleepiness Scale

- Sleep Studies eg Nocturnal oximetry, Video studies, Polysomnography

49
Q

What is polysomnography

A
  • 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
Q

How is sleep apnoea diagnosed

A
  • Using the apnoea/hypopnea index

- Or oxygen desaturation index

51
Q

Apnoea/hypopnea index (AHI) equation

A

AHI = (apnoeas + hypopnoeas) / total hours of sleep

52
Q

What co morbidities is sleep apnoea associated with (8)

A
  • Increased risk of accidents
  • Hypertension
  • Type 2 diabetes
  • Ischaemic heart disease
  • Heart failure
  • Cerebrovascular disease/stroke
  • Cardiac arrhythmias
  • Death
53
Q

What are the management goals for sleep apnoea

A
  • Resolve signs and symptoms of OSA
  • Improve sleep quality
  • Normalise apnoea-hypopnoea index (AHI) and oxyhaemoglobin saturation levels
54
Q

What can patients do to help with sleep apnoea

A
  • Weight loss
  • Avoid sleeping supine
  • Avoid alcohol
55
Q

Describe CPAP

A
  • Continuous Positive Airway Pressure (CPAP)
  • Device generates airflow => positive pressure delivered to airway via mask
  • Intraluminal pharyngeal pressure > surrounding pressure
  • Pharynx stays open
56
Q

When is CPAP used to treat sleep apnoea

A
  • 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
Q

Benefits of CPAP

A
  • Symptoms resolve
  • ↓ apnoea/hypopnoea
  • ↓ daytime sleepiness
  • ↓ risk road accidents
  • ↑ quality of life
  • Normalises BP
58
Q

Problems with CPAP

A
  • Adherence an issue
  • Airway drying/irritation (Can humidify)
  • Mask problems (Air leak, Comfort)
  • Normally life long treatment
59
Q

Treatment options for sleep apnoea

A
  • Mandibular advancement devices
  • CPAP
  • Surgery
60
Q

How do mandibular advancement devices work to treat sleep apnoea

A

They hold soft tissues of the oropharynx forward

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

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