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Anaesthetics > Oxygen therapy + airway management > Flashcards

Oxygen therapy + airway management Flashcards

1
Q

What percentage of oxygen is room air, that is adequate for healthy people?

A

21%

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2
Q

What are 3 categories that people requiring additional oxygen can be divided into?

A
  1. Respiratory disease - acute (pneumonia, oedema, asthma, ARDS) and chronic (COPD, fibrosis)
  2. Cardiac - arrhythmias, ischaemia, pulmonary oedema
  3. Generalised diseases - trauma, neuro, liver, renal, etc. - any severe disease may require elevated inspired oxygen
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3
Q

What are 2 examples of times when a small amount of additional oxygen is needed?

A
  1. Post-operatively
  2. Early pneumonia
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4
Q

What are 2 methods of delivering a small amount of additional oxygen?

A
  1. Nasal specs
  2. Simple face masks
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5
Q

What are 2 examples of times when a large amount of additional oxygen is required?

A
  1. Major trauma
  2. Sick patients e.g. in critical care
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6
Q

What are 2 examples of a need for control of oxygen concentration?

A
  1. Severe COPD - so they don’t lose their hypoxic drive
  2. Neonates on a ventilator
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7
Q

What does the graph show?

A
  • cyclical (normal) respiratory flow
  • lower line is inspiratory flow rate, dips are inspiration and longer peaks are expiration
  • Top line shows changes in oesophageal pressusre
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8
Q

What is the peak inspiratory flow rate in healthy patients? How does this compare with forced peak expiratory flow rate (peak flow)?

A

25-30L per minute (i.e. may be momentarily this fast as this is the maximum, within the full respiratory cycle)

Peak expiratory flow can be more than 10x this in healthy patients

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9
Q

What are three names for the simple face mask?

A
  1. Simple face mask
  2. Hudson mask
  3. Variable performance mask
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10
Q

How do simple face masks/variable face masks/Hudson masks work, and at what rate do they deliver oxygen?

A

Doesn’t give fixed inspired concentration but has a variable performance. Attached to 100% oxygen supply at 4-10L per minute

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11
Q

At what rate do Hudson face masks (variable performance/ simple face masks) deliver oxygen?

A

Deliver 100% oxygen a 4-10L per minute

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12
Q

Why do oxygen masks such as the simple face mask provide oxygen at several litres per minute to the patient?

A

As patient goes from 0L/minute at beginning of inspiration to peak of 25L/min, then back down to zero, there are points during the cycle when not enough oxygen is being delivered to match inspiratory flow

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13
Q

What is the structure of the Hudson/simple face mask and how does this enable it to work?

A

Has holes to breathe in through, and exhale out of them

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14
Q

Despite Hudson masks delivering 100% oxygen at 4-10L/minute, what is the actual percentage breathed in by a patient and why?

A

30-40% oxygen

when breathing in, we exceed the gas flow rate of the source (what mask is connected to) so entrain air (from outside mask) as well, so O2 concentrations falls. Conc. rises and falls as we breathe

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15
Q

When are nasal specs commonly used?

A

In post-operative period; also for domestic oxygen therapy

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16
Q

What are 2 advantages of nasal specs to deliver oxygen?

A
  1. Comfortable and well-tolerated
  2. Allow patients to eat - useful in patients who are v oxygen dependent who are eating, so they don’t become too hypoxic
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17
Q

What is a key disadvantage of nasal specs?

A

Deliver very variable oxygen concentrations - e.g. due to mouth breathing → room air, but much higher conc if entirely through nose. Some mixing occurs it the pharynx

(like variable performance mask but not such a variation in inspired oxygen)

18
Q

What are the approximately concentrations of oxygen delivered from nasal specs at the follows flow rates: 0, 1, 3, 4, 5, 6 L/min?

A

0: 21%
1: 25%
3: 29%
4: 33%
5: 41%
6: 45%

19
Q

How does the reservoir non-rebreathe mask work?

A
  • Oxygen from the source flows into the bag during expiration
  • Oxygen from the bag with some mixed air is breathed in during inspiration; there is enough oxygen in the bag to match the inspiratory flow rate
  • One-way valve prevents expired gas going into the bag (expired gas goes out through holes)
20
Q

What concentration of oxygen can be delivered using a reservoir non-rebreathe bag?

A

up to 80%

21
Q

Under what conditions can a reservoir non-rebreathe mask be used to deliver oxygen + why?

A

short-term use only as it contains dry gas with no humidification

22
Q

What is another name for Venturi-controlled concentration masks?

A

HAFOE: high air flow oxygen enrichment

23
Q

How do venturi masks work?

A
  • entrain (sweep along in its flow) air to general 30 L/min gas flow rate at a pre-determined concentration
  • fixed inspired concentration up to 30 L/min inspiratory flow rate
24
Q

What flow rates of oxygen and of air does a Venturi mask with oxygen concentration of 60% deliver?

A

Uses 15 L/min oxygen and entrains 15 L/min of air

25
Q

What kind of concentrations of oxygen do Venturi masks commonly use, and what for?

A

Low concentrations e.g. 24%, 28%, usually in late COPD (not appropriate in emergencies in otherwise well patients)

26
Q

What are the 6 Venturi mask concentrations and associated colours?

A
  • 24%: blue (bullies)
  • 28%: white (want)
  • 35%: yellow (your)
  • 40%: red (red)
  • 60%:green (grapes)
27
Q

What are 3 simple positional manoevres that can help open the airway in addition to adjuncts?

A

head tilt

chin lift

jaw thrust

28
Q

What are three advantages of the oropharyngeal airway (see picture)?

A
  1. Easy to insert and use
  2. No paralysis required
  3. Ideal for very short procedures
29
Q

What are 2 uses for oropharyngeal airways?

A
  1. Most often used as a bridge to a more definitive airway
  2. For very short procedures
30
Q

How does the laryngeal mask airway / LMA (see image) work?

A

Device sits in pharynx and aligns to cover the airway

31
Q

What are 2 advantages of the LMA during surgery?

A
  1. Very easy to insert
  2. Paralysis not usually required
32
Q

What are 2 disadvantages of the LMA?

A
  1. Poor control against reflux of gastric contents
  2. Not suitable for high pressure ventilation (small amount of PEEP {positive end-expiratory pressure} often possible)
33
Q

When are LMAs used in surgery?

A

commonly used for a wide range of anaesthetic uses, especially in day surgery

34
Q

What are 2 advantages of a tracheostomy?

A
  1. Reduces the work of breathing (and dead space)
  2. May be useful in slow weaning
35
Q

In what setting is tracheostomy widely used?

A

Percutaneous tracheostomy widely used in ITU

36
Q

What is a disadvantage and its consequence for tracheostomies?

A

Dries secretions, humidified air usually required

37
Q

What are 3 advantages of endotracheal tubes?

A
  1. Provides optimal control of the airway once the cuff is inflated
  2. may be used for long or short term ventilation
  3. Higher ventilation pressures can be used
38
Q

What are 2 disadvantages of the use of an endotracheal tube in surgery?

A
  1. Errors in insertion may result in oesophageal intubation (therefore end tidal CO2 usually measured to check)
  2. Paralysis often required
39
Q

How are nasopharyngeal airways inserted?

A

Lubricated and inserted into the nostril to provide a patent airway in patients with a decreased GCS. Come in a variety of sizes

40
Q

In what patients are nasopharyngeal airways used, and what does this make them ideal for?

A

Used in patients with a decreased GCS: ideal for patients having seizures (can’t insert oropharyngeal airway)

41
Q

In what group are nasopharyngeal airways relatively contraindicated in and why?

A

Relatively contraindicated in patients with base of skull fractures, as they can cause further damage

Anaesthetics (11 decks)

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