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103 Theme 4 - Lungs > Oxygen therapy and sleep apnoea > Flashcards

Oxygen therapy and sleep apnoea Flashcards

1
Q

What are the sources of oxygen in a hospital?

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

What units is oxygen delivered in?

A

–litres per minute

–percentage inspired oxygen

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3
Q

What are the features of 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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4
Q

What are the features of wall supply oxygen?

A
  • In hospital only
  • Central supply piped in to clinical areas
  • May not be available in all clinical areas (clinic rooms)
  • Supply 100% oxygen
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5
Q

What does the ball show?

A

Mid-point of ball marks flow rate.

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6
Q

What are the features of oxygen concentrators?

A
  • Mains operated machine
  • Molecular sieve- removes nitrogen
  • Oxygen predominant gas >90% concentration
  • Use in the home or when out
  • Regional suppliers with franchise for installation & support
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7
Q

What are the features of liquid oxygen?

A
  • More highly compressed
  • Larger gaseous volume per cylinder volume
  • Allow higher flow rates
  • Well developed in US & parts of Europe
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8
Q

What patient interfaces is there for sponataniously breathing patients?

A
  • Nasal cannulae
  • Uncontrolled masks (hudson, non-rebreathe)
  • Controlled (fixed percentage - venturi) masks
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9
Q

What are the features of nasal cannulae?

A
  • Usually well tolerated
  • Accepts flow rates 1-4L/min
  • Delivers 24-40% O2
  • % delivered depends on multiple factors
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10
Q

When would nasal cannulae be used?

A

Uses: mild hypoxaemia, not critically ill

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11
Q

What are the features of simple face masks?

A
  • Simple face mask
  • Hudson mask
  • Delivers 30-60% O2
  • Flow rate 5-10L/min
  • Mixing of O2, room air & exhaled air in mask
  • Used less often
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12
Q

What are the features of non-rebreathe masks?

A
  • Delivers 85-90% oxygen with 15L flow rate.
  • Bag: one-way valve stops:
  • mixing with room air
  • patient rebreathing expired air
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13
Q

When would a non-rebreathe mask be used?

A
  • Use: acutely unwell patients
  • Step down as soon as possible.
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14
Q

What are the features of venturi masks?

A
  • Controlled Oxygen
  • Venturi valve allows delivery of a fixed concentration of oxygen
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15
Q

Which mask has these options?

A

Venturi mask

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16
Q

How should oxygen be prescribed?

A

Oxygen should be prescribed on drug chart with target oxygen saturations.

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17
Q

What is oxygen a treatment for?

A

Oxygen is a treatment for hypoxaemia, not breathlessness.

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18
Q

What are the clinical indicators for oxygen?

A
  1. Acutely hypoxaemic patients
  2. Chronically hypoxaemic COPD patients with acute exacerbation
  3. Chronically hypoxaemic COPD patients who are stable
  4. Palliative use in advanced malignancy
    * Sats <90% and breathless, though often multifactorial
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19
Q

What are the target oxygen saturations?

A

•Normal young adult average = 96-98%

–Over 70yrs age 94-98%

  • Target in most patients = 94-98%
  • Target in those at risk of hypercapnic (high PaCO2) respiratory failure = 88-92%
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20
Q

Scenario 1: Acute breathlessness with hypoxaemia in a patient without significant background lung problems

What would be the causes of this?

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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21
Q

Scenario 1: Acute breathlessness with hypoxaemia in a patient without significant background lung problems

What is the risk and treatment?

A

Risk

Acute hypoxaemia => acute cardiac dysrhythmia & organ failure

Treatment

Maximal oxygen treatment.

High flow uncontrolled mask- first line

Alter flow and delivery device when stable

Target SpO2 = 94-98%

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22
Q

What else has to be done except oxygen when a patient is hypoxaemic?

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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23
Q

Who is at risk of hypercapnia (CO2 retention) if given high dose oxygen?

A

Chronic hypoxic lung disease

–COPD

–Bronchiectasis / Cystic fibrosis

Chest wall disease

–Kyphoscoliosis

–Thoracoplasty

Neuromuscular disease

Obesity related hypoventilation

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24
Q

Scenario 2: Chronically hypoxaemic patients with COPD who have an acute exacerbation

What is an exacerbation and what causes it?

A
  • Worsening of breathing in known COPD
  • Exacerbation may be viral or bacterial infection or episode of heart failure
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25
Q

Why do COPD patients often tolerate a lower PaO2 than “normal”?

A

Due to chronic hypoxaemia

They often rely on their hypoxaemic drive - if you over-correct their pO2 you may switch off their respiratory drive

Leading to:

  • further CO2 retention
  • worsening acidosis
  • Narcosis - reduced level of consciousness
  • (& death)
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26
Q

Scenario 2: Chronically hypoxaemic patients with COPD who have an acute exacerbation

How would you treat this patient?

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%
  • If not improving may need non-invasive ventilation
27
Q

Scenario 2: Chronically hypoxaemic patients with COPD who have an acute exacerbation

How to assess response to treatment?

A

Arterial blood gases, check frequently

  • pO2 <10
  • pCO2 falling from peak or maintained <6.0
  • pH increasing/maintained >7.35

Adjust dose of oxygen accordingly

28
Q

Scenario 2: Chronically hypoxaemic patients with COPD who have an acute exacerbation

Why not use nasal cannulae?

A

–potentially dangerous as actual inspired oxygen percentage varies according to the patient’s respiratory characteristics

–Uncontrolled therapy

29
Q

What are the British Thoracic Society’s guidelines for prescribing oxygen?

A

In Hospital, oxygen should be prescribed on the drug chart

State:

  1. the target oxygen saturation range
  2. the delivery device
  3. the “dose” – flow rate or percentage of inspired oxygen
30
Q

When would oxygen be used for chronically hypoxaemic patients?

A
  • Evidence for oxygen therapy only exists for patients with COPD
  • Also used in patients with interstitial lung disease and pulmonary hypertension
31
Q

What do chronically hypoxaemic patients who aren’t treated with oxygen develop?

A

–pulmonary hypertension

–right ventricular hypertrophy

–right ventricular failure (cor pulmonale)

–Secondary polycythaemia (raised Haemoglobin)

32
Q

What 2 studies looked at the effects of oxygen therapy of chronically hypoxaemic COPD patients?

A

–The MRC trial (UK)

•Increased survival in the oxygen group

–Nocturnal oxygen therapy trial - NOTT (US)

•1.96 times the deaths in the 12hour group

33
Q

When is long term oxygen treatment used?

A

For some patients with COPD

Specialist assessment:

–In patient’s stable state

–no sooner than 4 weeks after an exacerbation

34
Q

What are the indications for long term oxygen therapy?

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

35
Q

How is long term oxygen therapy provided?

A
  • Provided from an oxygen concentrator
  • Regional concentrator supply service
  • O2 treatment for ≥15 hours per day
36
Q

What are the benefits of long term oxygen therapy?

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 arryhthmias
  • Improved quality of life
37
Q

What are the benefits of portable oxygen?

A
  • May improve breathlessness in some patients
  • May extend duration of LTOT
38
Q

What are the negatives of portable oxygen?

A
  • Most patients breathlessness is not due to low pO2
  • Weight of cylinders
  • Duration of supply
39
Q

Define apnoea

A

Apnoea: “Cessation of Airflow” for 10 seconds or longer

40
Q

Define central

A

Central: Respiratory Control Centre - no respiratory effort

41
Q

Define obstructive

A

Obstructive: collapse of pharyngeal airway during sleep (continuation of respiratory effort)

42
Q

Define obstructive sleep apnoea (OSAHS)

A

Repetitive apnoeas and symptoms of sleep fragmentation with excessive daytime sleepiness.

5 or more apnoeas an hour

43
Q

Define hypopnoea

A

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

44
Q

Is sleep apnoea more common in women or men?

A

Men - 4%

Women - 2%

45
Q

What are the risk factors for sleep apnoea?

A

–Male sex

–Obesity

–Neck circumference greater than 43 cm (41cm women)

–Family history of obstructive sleep apnoea

–Smoking

–Alcohol/sedative use

–Craniofacial abnormalities (e.g retrognathia)

–Pharyngeal abnormalities (e.g. tonsillar enlargement)

–Some medical conditions (hypothryroidism, acromegaly, pregnancy)

–Sleeping supine

46
Q

Why is the prevelance of sleep apnoea increasing?

A

Increasing prevelance of obesity

47
Q

Complete the diagram

A
48
Q

What is the pathophysiology of sleep apnoea?

A

Pharynx:

↓ Upper airway (UA) neuromuscular tone

↓ UA caliber,

↑ UA resistance,

↑ pharyngeal compliance

=

Tendency of pharyngeal collapse

49
Q

Which anatomical features can cause sleep apnoea?

A
  • Nasal pathology: polyps, deviated septum
  • Enlarged Tonsils
  • Increased soft tissue e.g. obesity, hypothyroidism
  • Abnormal chin: micrognathia, retrognathia
  • Normal tongue relaxation + any causes of macroglossia
50
Q

What happens in sleep apnoea?

A
51
Q

What are the features of sleep apnoea?

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

52
Q

What are the complications of sleep apnoea?

A

•Cor pulmonale

–Right heart failure 2ndry respiratory disease

•Secondary Polycythaemia

–Excess of red blood cells

53
Q

What are the investigations for sleep apnoea?

A
  • Epworth Sleepiness Scale
  • Sleep Studies
  • Nocturnal oximetry
  • Video studies
  • Polysomnography
54
Q

How does the Epworth Sleepiness Scale work?

A

How likely are you to doze off or fall asleep during the following situations,
in contrast to just feeling tired?

For each of the situations listed below, give yourself a score of 0 to 3, where

0 = Would never doze; 1 = Slight chance; 2 = Moderate chance; 3 = High chance.

55
Q

What investigation is this?

A

Polysomnography (PSG)

56
Q

How is sleep apnoea diagnosed?

A

•Uses apnoea/hypopnea index (AHI)

–AHI = apnoeas + hypopnoeas / total sleep time in hours

  • Mild: AHI 5–14 per hour (+ symptoms/signs).
  • Moderate: AHI 15–30 per hour.
  • Severe: AHI more than 30 per hour.

•(Or oxygen desaturation index)

57
Q

What are the consequences of obstructive sleep apnoea?

A
  • Increased risk of accidents
  • Association with:

–Hypertension

–Type 2 diabetes

–Ischaemic heart disease

–Heart failure

–Cerebrovascular disease/stroke

–Cardiac arrhythmias

–Death

58
Q

What are the goals in management of sleep apnoea?

A
  • Resolve signs and symptoms of OSA
  • Improve sleep quality
  • Normalise:
  • apnoea-hypopnoea index (AHI)
  • oxyhaemoglobin saturation levels
59
Q

What is the management of sleep apnoea?

A

•Patient education – driving

  • DVLA website-guidance for medical professional
  • Must stop driving if excessive sleepiness
  • If moderate/severe OSAHS then DVLA will need medical confirmation of treatment/control/compliance.

•Behavioural change:

  • Weight loss
  • Avoid sleeping supine
  • Avoid alcohol
  • Treat contributing problems (e.g hypothyroidism)
  • Review medications - Sedating drugs, drugs causing weight gain
60
Q

What are the treatments for sleep apnoea?

A

•Mandibular advancement devices

–Hold soft tissues of oropharynx forward

–Mild-mod OSA, patient preference, failed CPAP

•? Surgery

–Most effective if severe, correctable, obstructing lesion

–Tonsillar or adenoid hypertrophy, craniofacial abnormalities

61
Q

How does CPAP work?

A

Continuous Positive Airway Pressure (CPAP)

–Device generates airflow => positive pressure delivered to airway via mask

–Intraluminal pharyngeal pressure > surrounding pressure

–Pharynx stays open

62
Q

What are the clinical indications for CPAP?

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
63
Q

What are the benefits of CPAP?

A
  • Symptoms resolve
  • ↓ apnoea/hypopnoea
  • ↓ daytime sleepiness
  • ↓ risk road accidents
  • ↑ quality of life
  • Normalises BP
64
Q

What are the problems associated with CPAP?

A
  • Adherence an issue
  • Airway drying/irritation - Can humidify
  • Mask problems
  • Air leak
  • Comfort

•Normally life long treatment

103 Theme 4 - Lungs (21 decks)

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