Oxygen Flashcards

1
Q

What is a type 1 respiratory failure

A
  • this is when the partial pressure of oxygen in the blood is below 8kPa
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2
Q

what is type 2 respiratory failure

A
  • this is when the partial pressure of carbon dioxide is >6.1kPa and the partial pressure of oxygen is less than 8 kPa
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3
Q

How must a simple face mask be used

A

= 5-10l/min
= delivered oxygen concentration of 40-60%
- not the best intimal oxygen delivery device

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4
Q

what should a nasal cannulae not be used above

A
  • should not be used above 6l/min as there is a significant risk of drying out the airways
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5
Q

what are the advantages and disadvantages of a nasal cannulae

A

Advantage
- more comfortable

Disadvantage

  • can cause nasal irritation
  • cannot determine the actual FiO2 that is given to the patient
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6
Q

When are venturi masks used

A
  • when there is a risk of hypercapnic respiratory failure
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7
Q

When is a high concentration reservoir mask used

A
  • mainly used if a patient has a critical illness such as trauma or cardiac arrest
  • flow rate is 15l/min
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8
Q

What is high flow humidified oxygen

A
  • this system can deliver a flow rate between 2-60l/min and oxygen concentration between 21-100%
  • has a small positive airway pressure effect to reduce the work of breathing
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9
Q

When is CPAP used

A
  • CPAP is a type of ventilatory support
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10
Q

when should a repeat ABG be done if the patient is at risk of hypercapnia respiratory failure

A
  • this must be done within 30-60 minutes of starting or any change in oxygen delivery
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11
Q

How does the high concentration reservoir bag work

A
  • fills with oxygen from the wall when connected to the flow meter
  • patient will be able to breathe in the oxygen contained within this bag
  • face mask - connected to the reservoir bag via the connector
  • the fitting of the mask can be adjusted by the nose clip and the adjustable straps
  • there are two exhalation ports on each side where air leaves so it cannot be rebreathed
  • connector stops this as it is a one way valve
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12
Q

what is the key thing you should do with the reservoir bag

A
  • do not put the oxygen bag on the patient until the reservoir bag has been sufficiently inflated
  • the oxygen the patient breathes in comes from the bag and it must be inflated first
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13
Q

What do oxygen saturations represent

A
  • they represent how much of the saturated the haemoglobin within the body is with oxygen e.g. how much of the haemoglobin is bound with oxygen as a percentage
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14
Q

What are the two main ways to measure oxygen saturations

A
  • pulse oximetery - SpO2

- ABG - SaO2

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15
Q

What is hypoxaemia

A
  • this is when the partial pressure of oxygen in the blood is low
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16
Q

what is partial pressure of oxygen

A
  • this is how much pressure is exerted by oxygen
17
Q

What is the difference between PAo2

and PaO2

A
  • PAO2 - is the partial pressure of oxygen within the alveoli
  • PaO2 - is the partial pressure of oxygen within the blood (artery)
18
Q

the amount of oxygen that…

A

binds to haemoglobin is dependent on the partial pressure of oxygen in the blood

19
Q

describe the shifts that can happen on a oxygen dissociation curve

A
  • A shift tot he left makes oxygen binding easier

- A shift to the right makes oxygen dissociation easier

20
Q

What makes the oxygen curve shift to the right

A
  • increased 2,3-DPG
  • increase in temperature
  • increased in PCO2
  • decreased pH
21
Q

What is 2,3-DPG

A
  • this is a product of anaerobic metabolism
  • as red cells don’t have any mitochondria they undergo anaerobic metabolism
  • the 2,3-DPG they produce bind strongly to haemoglobin than oxygen
22
Q

What is the initial device that you should use in someone who is at risk of hypercapnia respiratory failure

A
  • 28% venturi mask at 4 l/min

or

  • Nasal cannulae at 1-2 L/min
23
Q

If a patient has had a previous hypercapnia respiratory failure what should there initial oxygen therapy be

A
  • 24% venturi mask at 2-3 l/min
  • 28% venturi mask at 4 l/min
  • nasal cannulae at 1-2 L/min
24
Q

What do they think is the main cause of oxygen induce hypercapnia now

A
  • due to ventilation/perfusion mismatch
25
Q

describe V/Q mismatch

A
  • int he lung there can be areas where the ventilation is higher than perfusion V/Q >1
  • there can be areas in which the ventilation is lower than the perfusion V/Q<1
  • the optimal setup is when ventilation and perfusion are match V/Q = 1
26
Q

What happens to the V/Q ratio in hypoxic conditions

A
  • in hypoxic conditions the lung diverts blood away from the under ventilated areas of the lung by a process known as hypoxic vasoconstriction
  • if oxygen is given to these patients you limit the body’s ability to vasoconstriction these blood vessels, this leads to further blood flow to the under ventilated areas so more carbon dioxide moves into the blood; this increases the PaCO2
27
Q

what are the differences between the venturi masks

A
  • colour and shape are different
  • side port size is different
  • percentage oxygen flow is different
28
Q

How does the ventriloquist’s valve work

A
  • the tubing is connected to the venturi valve and oxygen from the wall enters the valve at the specified flow rate
  • the oxygen that is delivered from the wall (100%) is diluted by room air (21%) that enters via ports not he side by the venturi principle
  • the different amounts of air that come into the valve is determined by the size of the side ports, the flow rate of oxygen and the hole within the valve
  • the final mixture of oxygen then goes into the mask to be breathed in by the patient
29
Q

What is the venturi principle

A
  • a small hole creates a reduction in pressure which entrains room air to deliver the desired final percentage of oxygen to the patient
30
Q

if the patients has a respiratory rate >30 breaths per minute the flow rate of the current venturi mask should be…

A

increased above the maximum flow rate first before changing the valve

31
Q

What conditions increase a patient of having type 2 respiratory failure

A
  • myasthenia gravis
  • kyphoscoliosis
  • obesity hypoventilation syndrome
  • obstructive sleep apnoea
  • COPD
32
Q

How often should someone with COPD have there ABG checked

A

30-60 minutes after change to the oxygen therapy

33
Q

When can a COPD patient have oxygen saturations changed to 94-98%

A
  • if a patient with COPD normal ABG post initiation of oxygen therapy

unless:
- they have a previous history of hypercapnia respiratory failure that required NIV or intermittent positive pressure ventilation
- or the patients usual oxygen saturations are below 94%