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Theme 4 > Principles of Oxygen Therapy and sleep apnoea > Flashcards

Principles of Oxygen Therapy and sleep apnoea Flashcards

1
Q

Oxygen cylinder

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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2
Q

Wall supply

A

In hospital only
Central supply piped in to clinical areas
Not every ward has this
Supply 100% oxygen

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3
Q

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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4
Q

Liquid oxygen

A

More highly compressed
Larger gaseous volume per cylinder volume
Well developed in US & parts of Europe

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5
Q

Patient interfaces

A

For spontaneously breathing patients:
Nasal cannulae
Uncontrolled masks (hudson, non-rebreathe)
Controlled (fixed percentage - venturi) masks

Oxygen reaches the patient either as:
litres per minute
percentage inspired oxygen

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6
Q

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

Uses: mild hypoxaemia, not critically ill

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7
Q

Uncontrolled masks - simple face mask

A 
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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8
Q

Uncontrolled masks - non rebreathe mask

A 
Delivers 85-90% oxygen with 15L flow rate. 
Bag: one-way valve stops:
mixing with room air 
patient rebreathing expired air
Use: acutely unwell patients 
Step down as soon as possible.
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9
Q

Venturi mask

A

Controlled Oxygen

Venturi valve allows delivery of a fixed concentration of oxygen

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10
Q

Clinical indications

A

Oxygen is a treatment for hypoxaemia, not breathlessness.

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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11
Q

Target oxygen saturation - Normal adult average

A

96-98%

Minimal reduction with age

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12
Q

Target oxygen saturation - Most patients

A

94-98%

Balance of what is normal and what is safe

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13
Q

Target oxygen saturation - Those at risk of hypercapnic

A

88-92%

May be lower for some

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14
Q

Remember not just about oxygen

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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15
Q

Hypercapnia (CO2 retention) risk with high oxygen dose

A 
Chronic hypoxic lung disease 
- COPD 
- Bronchiectasis / Cystic fibrosis 
Chest wall disease 
- Kyphoscoliosis 
- Thoracoplasty 
Neuromuscular disease 
Obesity hypoventilation
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16
Q

Aims of treatment

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%

17
Q

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

If not improving may need non-invasive ventilation

18
Q

Don’t always use nasal cannulae

A
  • potentially dangerous as actual inspired oxygen percentage varies according to the patient’s respiratory characteristics
  • Uncontrolled therapy
19
Q

Prescribing Oxygen - British Thoracic Society Guidelines

A

State:
the target oxygen saturation range
Depends on the clinical scenario
the delivery device
Controlled vs uncontrolled (venturi or nasal cannulae)
the “dose” – flow rate or percentage of inspired oxygen
You may provide a range here to guide ward staff
But may be more important to work to saturation targets

Patients may carry an ‘oxygen treatment card’ with their recommended oxygen saturations/prescription.

20
Q

When to suggest long term oxygen treatment

A

For some patients with COPD

Specialist assessment:

  • In patient’s stable state
  • ABGs on 2 occasions at least 3 weeks apart to demonstrate clinical stability
  • no sooner than 4 weeks after an exacerbation
21
Q

Long term oxygen treatment indications

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 pulmonary hypertension
22
Q

Long term oxygen treatment

A

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

23
Q

Benefits of long term oxygen treatment

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
24
Q

Portable oxygen

A

May improve breathlessness in some patients
May extend duration of LTOT

But ….
Most patients breathlessness is not due to low pO2
Weight of cylinders
Duration of supply

25
Q

Apneoa

A

“Cessation of Airflow” for 10 seconds or longer

26
Q

Obstructiuve

A

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

27
Q

OSA

A

5 or more obstructive apnoeas per hour.

28
Q

Hypopneoa

A

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

29
Q

Apneoa risk factors

A

Male sex
Obesity
Neck circumference greater than 43 cm (41cm women)
Family history of OSAS
Smoking
Alcohol/sedative use
Craniofacial abnormalities (e.g retrognathia)
Pharyngeal abnormalities (e.g. tonsillar enlargement)
Some medical conditions (hypothryroidism, acromegaly, pregnancy)
Sleeping supine

30
Q

Clinical features of apnoea

A 
Snoring (Hx often from partner)
Nocturnal choking/waking with a “start” 
Unrefreshing/restless sleep
Morning dry mouth
Morning headaches
Excessive daytime sleepiness

Nocturia

31
Q

Apnoea investigation

A 
Epworth Sleepiness Scale
Sleep Studies
Nocturnal oximetry
Video studies
Polysomnography
32
Q

Consequences of OSA

A 
Increased risk of accidents
Association with:
- Hypertension 
- Type 2 diabetes
- Ischaemic heart disease
- Heart failure
- Cerebrovascular disease/stroke
- Cardiac arrhythmias
- Death
33
Q

Management

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

Multi-disciplinary approach needed

34
Q

Mandibular advancement devices

A

Hold soft tissues of oropharynx forward

Mild-mod OSA, patient preference, failed CPAP

35
Q

Continuous Positive Airway Pressure (CPAP)

A

Device generates airflow => positive pressure delivered to airway via mask
Intraluminal pharyngeal pressure > surrounding pressure
Pharynx stays open

36
Q

CPAP benefits

A 
Benefits
Symptoms resolve
↓ apnoea/hypopnoea
↓ daytime sleepiness
↓ risk road accidents
↑ quality of life
Normalises BP
37
Q

CPAP problems

A 
Adherence an issue
Airway drying/irritation
Can humidify
Mask problems
Air leak
Comfort
Life long treatment

Theme 4 (16 decks)

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