oxygen therapy & sleep apnoea Flashcards
1
Q
what are the different oxygen sources?
A
- oxygen cylinders
- wall supply
- oxygen concentrators
- liquid oxygen
2
Q
what units is oxygen delivered in?
A
litres per minute
3
Q
oxygen cylinders?
A
- widely available
- various sizes
- limited length of supply
- suitable for limited/short duration treatment
- relatively expensive
- supply 100% oxygen
4
Q
wall supply oxygen?
A
- in hospital only
- central supply piped into clinical areas
- may not be available in all clinical areas
- supply 100% oxygen
5
Q
what marks the flow rate for wall supply oxygen?
A
mid-point of the ball
6
Q
oxygen concentrators?
A
- mains operated machine
- molecular sieve: removes nitrogen
- oxygen predominant gas >90% concentration
- used in home or when out
- regional suppliers with franchise for installation and support
7
Q
liquid oxygen?
A
- more highly compressed
- larger gaseous volume per cylinder volume
- allow higher flow rates
- well developed in US and parts of Europe
8
Q
how do you supply oxygen to spontaneously breathing patients?
A
- nasal canulae
- uncontrolled masks (hudson, non-rebreathe)
- controlled masks (venturi)
9
Q
what are the 2 ways oxygen reaches patients?
A
- litres per minute
- percentage inspired oxygen
10
Q
nasal cannulae?
A
- well-tolerated
- accepts flow rates 1-4L/min
- delivers 24-40% oxygen
- % delivered depends on multiple factors
11
Q
what are the uses of nasal cannulae?
A
mild hypoxaemia, not critically ill
12
Q
what are the negatives of nasal cannulae?
A
- can’t provide humified oxygen
- can cause bleeding, crusting
13
Q
simple face mask - hudson mask?
A
- delivers 30-60% oxygen
- flow rate 5-10L/min
- mixing of oxygen, room air and exhaled air in mask
- used less often
14
Q
what are the negatives of uncontrolled masks?
A
can’t fix oxygen intake
15
Q
non-rebreathe masks?
A
- delivers 85-90% oxygen with 15L flow rate
- bag: one way valve stops mixing with room air and patient rebreathing expired air
16
Q
what are the uses of non-rebreathe masks?
A
acutely unwell patients - step them down as soon as possible
17
Q
venturi mask?
A
- controlled oxygen
- venturi valve allows delivery of a fixed concentration of oxygen
18
Q
what do the different colours mean in venturi masks?
A
- blue = 2-4L/min, 24% oxygen
- white = 4-6L/min, 28% oxygen
- yellow = 8-10L/min, 35% oxygen
- red = 10-12L/min, 40% oxygen
- green = 12-15L/min, 60% oxygen
19
Q
when do you usually use oxygen to treat patients?
A
- acutely hypoxaemic patients
- chronically hypoxaemic COPD patients with acute exacerbation
- chronically hypoxaemic COPD patients who are stable
- palliative use in advanced malignancy (stats <90%)
20
Q
what are the target oxygen saturations?
A
- normal young adult = 96-98%
- over 70s = 94-98%
- most patients = 94-98%
- those at risk of hypercapnia = 88-92%
21
Q
what is hypercapnia?
A
high carbon dioxide levels
22
Q
who is at risk of hypercapnia if given a high dose of oxygen?
A
- chronic hypoxic lung disease (COPD, bronchiectasis/cystic fibrosis)
- chest wall disease: kyphoscoliosis, throacoplasty
- neuromuscular disease
- obesity-related hypoventilation
23
Q
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
- if not improving may need non-invasive ventilation
24
Q
who can not use nasal cannulae?
A
- potentially dangerous as actual inspired oxygen percentage varies according to the patients respiratory characteristics
- uncontrolled therapy
25
how do you prescribe oxygen?
- in-hospital oxygen should be prescribed on the drug chart
- state: 1) target oxygen saturation range 2) the delivery device 3) the 'dose' - flow rate or percentage of inspired oxygen
- patients may carry an oxygen treatment card with their recommended oxygen saturations/prescriptions
26
when would you consider long term oxygen treatment (LTOT)?
- for some patients with COPD
| - specialist assessment: in patients stable state, no sooner than 4 weeks after an exacerbation
27
what are the indicators for long term oxygen treatment?
- COPD patients with pO2 <7.3kPa
OR
- COPD patients with pO2 7.3<8kPA and secondary polycythaemia, nocturnal hypoxemia, peripheral oedema/evidence of right ventricular failure or evidence of pulmonary hypertension
28
what is long term oxygen treatment?
- provided from an oxygen concentrator
- regional concentrator supply service
- O2 treatment for >15 hours per day
29
what are the benefits of long term oxygen treatment?
- 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
30
portable oxygen?
- may improve breathlessness in some patients
- may extend the duration of LTOT
- but most patients breathlessness is not due to low pO2, weight of cylinders, duration of supply
31
what is apnoea?
cessation of airflow for 10 seconds or longer
32
what is central?
respiratory control centre - no respiratory effort
33
what is obstructive?
collapse of pharyngeal airway during sleep
34
what is OSA?
5 or more obstructive apnoeas per house
35
what is hypopnea?
reduction in airflow by 50% accompanied by desaturation of 4% and/or arousal from sleep
36
what are the risk factors for sleep apnoea?
- male sex
- obesity
- neck circumference (43cm men & 41cm women)
- family history of OSAHS
- smoking
- alcohol/sedative use
- craniofacial abnormalities
- pharyngeal abnormalities
- some medial conditions
- sleeping supine
37
what happens in sleep apnoea?
- 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
REPEAT CYCLE
38
what are the clinical features of sleep apnoea?
- snoring
- nocturnal chocking/waking with a start
- unrefreshing/restless sleep
- morning dry mouth
- morning headaches
- excessive daytime sleepiness: difficulty concentrations, mood changes, sleeping at inappropriate times
- nocturia
- complications: cor pulmonale and secondary polycythaemia
39
how do you diagnose sleep apnoea?
- uses apnoea/hypopnea index (AHI)
- AHI = apnoeas + hypopneas / 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
40
what are the consequences of OSA?
```
- increased risk of accidents
association with:
- hypertension
- type 2 diabetes
- ischemic heart disease
- heart failure
- cerebrovascular disease/stroke
- cardiac arrhythmias
- death
```
41
what are the goals for managing sleep apnoea?
- resolve signs and symptoms of OSA
- improve sleep quality
- normalise: apnoea-hypopnea index, oxyhaemoglobin saturation level
- multidisciplinary approach needed
- patient education
- mandibular advancement devices
- surgery
- continuous positive airway pressure (CPAP)
42
when do you use CPAP?
- patients with mild OSAHS and additional co-morbidities
- patients with mild OSAHS and high risk profession
- patients with moderate/severe OSAHS regardless of symptoms
- but not patients with mild OSAHS no additional risk factors who aren't excessively sleepy
43
what are the benefits of CPAP?
- symptoms resolve
- decreased apnoea/hypopnoea
- decreased daytime sleepiness
- decreased risk of road accidents
- increased quality of life
- normalises BP
44
what are the problems with CPAP?
- adherence an issue
- airway drying/irritation (can humidity)
- mask problems (air lead, comfort)
- normally life long treatment
