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Flashcards in Oxygen Therapy Deck (51)
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what is the percentage of oxygen in the air



why does the oxygen decrease from the atmosphere into the lung

- mixing with dead space gases
- water vapour


describe the oxygen cascade

- Oxygen starts as dry atmospheric gas at 21 kPa
- it becomes humidified tracheal gas at 19.8 kPa
- alveolar gas it turns to 14 kPa due to mixing with dead space
- in arterial gas it goes down to 13.3 kPa
- in capillary blood it is 6-7 kPa
- and in the mitochondria it is 1-5 kPa


What does the oxygen bind to in haemoglobin



Describe how oxygen binds to haemoglobin

- its difficult for the first oxygen to bind to the haemoglobin
- once that first oxygen molecule binds there is a conformation change and then oxygen binds to the haemoglobin more easily


describe what the oxygen haemoglobin dissociation curve shows you

- shows the change in saturation with the change in partial pressure of oxygen
- sigmoid shape due to the binding of oxygen to haemoglobin - first oxygen molecule is hard to bind but the conformation change makes it easier to bind


What shifts the oxygen dissociation curve right

- high carbon dioxide
- increase in temperature
- pH - increase in acid (lower pH)
- exercise
- 2,3- DPG


What shift the oxygen dissociation curve to the left

- lower CO2
- higher pH
- lower temperature


What happens when the oxygen dissociation curve is shifted to the right

- oxygen release is easier


What are the two ways in which oxygen is delivered in a hospital setting

- wall oxygen
- cylinder oxygen


how do you classify what oxygen supply patients should receive

- Critical patients
- most patients
- selected COPD patients


What should the oxygen saturation not be below

- below 90/94


If patients have an oxygen saturation above ...

94% then you don't need to deliver oxygen


what is the target oxygen stats for patients with COPD

- 88-92%
- these patients are at risk of hypercapnia respiratory failure


What is the target stats for all other patients

- greater than 94%


How should you administer oxygen in patients with COPD

- venturi masks in patients with COPD


How do you measure oxygen saturations

- pulse oximetry


What are the BTS oxygen prescribing guidelines

- Critical illness requires high levels of oxygen supplementation
- serious illness requires moderate level of oxygen if the patient is hyperaemic
- COPD and other conditions require controlled or low-dose oxygen therapy
- conditions for which patients should be monitored closely but oxygen therapy is not required unless the patient is hypoxaemic


What are the dangers of oxygen

- free radicalisation - oxygen toxicity
- flammable - explosive
- loss of hypoxic drive
- cause vasoconstriction


Name the 4 oxygen delivery devices

- venturi mask
- face mask
- nasal cannulae
- resovoir bag with face mask


Who is the nasal cannulae suitable for

- for most patients with type 1 or type II respiratory failure


How much oxygen can the nasal cannulae give

- 2-5L a minute gives approximately 24-50% FIO2
- range as its not a fixed performance device - breath through your mouth


What does the FIO2 depend on in nasal cannulae

- oxygen flow rate
- patients minute volume
- inspiratory flow
- pattern of breathing


What are the benefits of nasal cannulae

- comfortable and easily tolerated
- no re-breathing
- low cost


Who do you use a simple face mask for

Type 1 respiratory failure


What is type 1 respiratory failure

hypoxia less than 8 kPa but no hypercapnia


What is type 2 respiratory failure

Hypoxia and hypercapnia


Describe what flow the simple face masks gives

- variable oxygen concentration between 35% and 60%
- flow rate is 5-10L/min
- flow must be at least 5L/min to avoid carbon dioxide build up


In simple face masks what must the flow rate be above

- flow must be at least 5L/min to avoid carbon dioxide build up


What are the benefit and disadvantages of a simple face mask

- low cost

- uncomfortable