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T2: Theme 4: Lungs > Lecture 6: O2 therapy and sleep apnoea > Flashcards

Lecture 6: O2 therapy and sleep apnoea Flashcards

1
Q

What are the four main sources of O2?

A

Oxygen Cylinders
Wall Supply
Oxygen Concentrators
Liquid Oxygen

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2
Q

How is O2 delivered (units)?

A

Litres per minute
OR
Percentage inspired oxygen

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3
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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4
Q

Describe wall supply.

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

Describe O2 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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6
Q

Describe liquid O2.

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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7
Q

What are the 3 ways to administer O2 (patient interfaces)?

A

Nasal cannulae

Uncontrolled masks (hudson, non-rebreathe)

Controlled (fixed percentage - venturi) masks

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8
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

Uses: mild hypoxaemia, not critically ill

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9
Q

What are the advantages and disadvantages of nasal cannulae?

A

Advantages:

  • Means they can still eat/drink
  • Less claustrophobic
  • Can talk

Disadvantages:

  • Limited flow rate
  • Uncomfortable (can get breakdown of the skin, drying out
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10
Q

Describe uncontrolled 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 - used when first arrive (during triage then change)

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11
Q

Describe uncontrolled masks.

A

Non-rebreathe mask

Delivers 85-90% oxygen with 15L flow rate

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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12
Q

Describe venturi mask.

A

Controlled Oxygen

Venturi valve allows delivery of a fixed concentration of oxygen

Used for patients with COPD (where worried about chronic hypoxia)

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13
Q

When is O2 treatment indicated?

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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14
Q

Why might a patient have low O2?

A 
Chest infections (pneumonia)
Pneumothorax 
Emphysema 
Asthma 
CO poisoning 
Shock
Pulmonary embolism
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15
Q

What are the target O2 sats?

A

Normal young adult average = 96-98%

Over 70yrs age = 94-98%

Target in most patients = 94-98%
Balance of what is normal and what is safe

Target in those at risk of hypercapnic (high PaCO2) respiratory failure = 88-92%
(may be lower for some)

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16
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

17
Q

Why are some people at risk of hypercapnia (CO2 retention) if given high dose oxygen?

A

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)

You can kill the patient with oxygen

Hypoxaemia may still be a risk to them

18
Q

What three things need to be stated when prescribing O2?

A

Target oxygen saturation range - depends on the clinical scenario

Delivery device - controlled vs uncontrolled (venturi or nasal cannulae)

“Dose” – flow rate or percentage of inspired oxygen

19
Q

What are the indications for COPD patients to receive 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
20
Q

What is LTOT?

A

Provided from an oxygen concentrator

Regional concentrator supply service

O2 treatment for ≥15 hours per day

21
Q

What are the benefits of LTOT?

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

22
Q

What is apnoea?

A

“Cessation of Airflow” for 10 seconds or longer

23
Q

What is central apnoea?

A

Respiratory Control Centre - no respiratory effort

24
Q

What is obstructive apnoea?

A

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

25
Q

What is obstructive sleep apnoea?

A

5 or more obstructive apnoeas per hour

26
Q

What is hypopnoea?

A

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

27
Q

What are the risk factors for sleep apnoea?

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
28
Q

What are the three regions of the pharynx?

A

Nasopharynx
Oropharynx
Laryngopharynx

29
Q

What pharyngeal abnormalities may increase risk of apnoea?

A

Nasal pathology (polyps, deviated septum)

Enlarged tonsils

Increased soft tissue (obesity, hypothyroidism)

Abnormal chin (micrognathia, retrognathia)

30
Q

What causes the pharynx to collapse?

A

↓ UA neuromuscular tone
↓ UA caliber
↑ UA resistance
↑ pharyngeal compliance

31
Q

What are the clinical 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
32
Q

What are the possible complications of sleep apnoea?

A

Cor pulmonale - right heart failure secondary respiratory disease

Secondary Polycythaemia - excess of red blood cells

33
Q

What can be used to assess sleep apnoea?

A

Epworth Sleepiness Scale

Sleep Studies

  • Nocturnal oximetry (measure o2 and pulse over night)
  • Video studies
  • Polysomnography (detailed measurements of nasal flow and movement of the chest)
34
Q

How do you diagnose sleep apnoea?

A

AHI = apnoeas + hypopnoeas / total sleep time in hours

Mild: AHI 5–14per hour (+ symptoms/signs)

Moderate: AHI 15–30per hour

Severe: AHI more than 30per hour

35
Q

What are the consequences of OSA?

A 
Hypertension 
Type 2 diabetes
Ischaemic heart disease
Heart failure
Cerebrovascular disease/stroke
Cardiac arrhythmias
Death

Increased risk of accidents

36
Q

How can you treat OSA?

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

Continuous Positive Airway Pressure (CPAP)

37
Q

What is CPAP?

A

Device generates airflow

Positive pressure delivered to airway via mask

Intraluminal pharyngeal pressure > surrounding pressure

Pharynx stays open

38
Q

What are the benefits of CPAP?

A 
Symptoms resolve
↓ apnoea/hypopnoea
↓ daytime sleepiness
↓ risk road accidents
↑ quality of life
Normalises BP
39
Q

What are the problems with CPAP?

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

T2: Theme 4: Lungs (16 decks)

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