Respiratory Support ✅ Flashcards
(112 cards)
1
Q
What is respiratory failure defined as?
A
A syndrome of inadequate gas exchange
2
Q
What is the result of the inadequate gas exchange in respiratory failure?
A
Arterial oxygen, carbon dioxide, or both cannot be maintained within their normal ranges
3
Q
What is the normal oxygen PaO2?
A
> 11kPa
4
Q
What is the normal carbon dioxide PaCO2?
A
<6.0kPa
5
Q
What is the normal arterial-alveolar oxygen tension difference PA-aO2?
A
10-25mmHg (in room air)
6
Q
What is a drop in arterial oxygenation termed?
A
Hypoxaemia
7
Q
What is a rise in arterial carbon dioxide levels termed?
A
Hypercapnia
8
Q
What determines the classification of respiratory failure into type I and II?
A
Absence or presence of hypercapnia respectively
9
Q
What is type 1 respiratory failure defined as?
A
Hypoxia without hypercapnia (PaCO2 may be normal or low)
10
Q
What is type 1 respiratory failure typically caused by?
A
V/Q mismatch
11
Q
What is meant by V/Q mismatch?
A
The volume of air flowing in and out of the lungs is not matched with the flow of blood to the lungs
12
Q
What categories of conditions can cause type 1 respiratory failure?
A
- Parenchymal diseases
- Interstitial lung diseases
- Shunts
13
Q
Give 3 interstitial lung diseases that can cause type 1 respiratory failure?
A
- ARDS
- Pneumonia
- Emphysema
14
Q
What kind of shunt can cause type 1 respiratory failure?
A
Right to left shunt
15
Q
What is type 2 respiratory failure defined as?
A
Hypoxia with hypercapnia
16
Q
What is the mechanism of type 2 respiratory failure?
A
Inadequate ventilation
17
Q
What are the categories of causes of type 2 respiratory failure?
A
- Increased airway resistance
- Neurological hypoventilation
- Neuromuscular problems
- Decreased functional residual capacity
18
Q
Give 3 causes of increased airway resistance
A
- Croup
- Bronchiolitis
- Asthma
19
Q
Give 2 causes of neurological hypoventilation
A
- Drug effects
- Brain stem lesions
20
Q
Give 2 neuromuscular problems causing type 2 respiratory failure
A
- Guillain-Barre syndrome
- Congenital myopathy
21
Q
Give 4 causes of reduced functional residual capacity
A
- Kyphoscoliosis
- Chest deformity
- Pneumothorax
- Flail chest
22
Q
What can respiratory failure lead to if untreated?
A
End organ damage and death from hypoxia
23
Q
What is the purpose of respiratory support in respiratory failure?
A
To prevent progression to organ damage and death, and maintain life while the underlying condition is treated
24
Q
What does respiratory support range from?
A
Oxygen by face mask, to non-invasive support, endotracheal intubation and mechanical ventilation, and extracorporeal membrane oxygenation (ECMO)
25
Which children should receive oxygen support?
Children with SpO2 <92% in air
26
What happens at a SpO2 below 92%?
The oxygen haemoglobin dissociation curve becomes steep, and delivery of oxygen to the tissues becomes compromised
27
What can high concentration inspired oxygen cause?
Direct cellular toxicity and reabsorption atelectasis
28
What is the result of both high and low oxygen concentrations being damaging?
The amount of inspired oxygen should be titrated according to pulse oximetry
29
What does a fixed performance, high flow mask provide?
Fractional inspired oxygen concentration (FiO2) within range of 0.26-0.6
30
When might the FiO2 not be known?
With the more common variable performance masks, or with nasal cannulae
31
What FiO2 is usually provided with variable performance masks/nasal cannulae?
<0.4
32
What is the maximum FiO2 via face mask?
0.6
33
When can the FiO2 via face mask be increased above 0.6?
If reservoir bag is used
34
What FiO2 will be delivered using high flow oxygen (15L/min) delivered by face mask with reservoir bag?
Up to 0.9
35
What are the main indications for intubation and ventilation in respiratory failure?
- Severe respiratory distress
- Tiring due to excessive work of breathing
- Progressive hypoxaemia
- Reduced conscious level
- Progressive neuromuscular weakness, e.g. Guillain-Barre syndrome
36
What are the methods of delivering non-invasive ventilation?
- Tight fitting face mask
- Nasal masks
- Prongs
- Hood
37
What is the main advantage of NIV?
Endotracheal intubation can be avoided, along with the complications of mechanical ventilation
38
Give an example of a complication of mechanical ventilation
Ventilator-associated pneumonia
39
What are the two main modalities of NIV?
CPAP and BiPAP
40
What does CPAP stand for?
Continuous positive airway pressure (CPAP)
41
What pressure is used for CPAP?
+5 to +10cm H20
42
What are the beneficial effects of CPAP?
- Reduced alveolar collapse
- Improved oxygenation via alveolar recruitment
- Reduced work of breathing
43
What are the disadvantages of CPAP?
- Skin necrosis at interface between face mask and skin
- Stomach distention
- Risk of aspiration
44
What does BiPAP stand for?
Biphasic positive airways pressure
45
What is BiPAP?
A mode of ventilation where two levels of pressure are set - inspiratory pressure (IPAP) and expiratory pressure (EPAP)
46
What do most modern BiPAP ventilators allow?
The patient to breathe spontaneously
47
How do BiPAP ventilators allow the patient to breathe spontaneously?
By detecting inspiration and expiration via pressure or flow changes in the ventilator circuit
48
What is usually set in case of apnoea in BiPAP circuits?
A fixed back-up respiratory rate
49
What are the main modes of invasive ventilation in children?
- Intermittent mandatory ventilation (IMV)
| - High frequency oscillatory ventilation (HFOV)
50
What can IMV be divided into?
Pressure control (PC) and volume control (VC) ventilation
51
What is set in PC ventilation?
- Peak inspiratory pressure (PIP)
- Positive end expiratory pressure (PEEP)
- Inspiratory time (Tinsp)
- Ventilator rate
- Inspired oxygen
52
What does expiration depend on when inspired breaths are delivered actively by the ventilator in PC ventilation?
The elastic recoil of the chest
53
What determines the delivered tidal volume (TV) in PC ventilation?
- PIP
- Tinsp
- Lung compliance
54
What is meant by 'synchronised mode' in PC ventilation?
The ventilator delivers the PIP when the patient takes a breath
55
What is synchronised mode in PC ventilation also known as?
Synchronised intermittent mandatory ventilation (SIMV-PC)
56
When is SIMV-PC useful?
When ventilating non-paralysed patients and for weaning
57
What happens in VC ventilation?
The patient is ventilated at a preset tidal volume (TV) and rate.
PEEP and inspired oxygen concentration is also set
58
What is the result of the tidal volume being fixed in VC ventilation?
The pressure required to deliver the tidal volume varies depending on lung compliance
59
What might result from non-compliant lungs with VC ventilation?
High peak airway pressure and associated barotrauma (ventilator associated lung injury, VALI)
60
What is the result of VC ventilation being associated with a risk of VALI?
Volume modes of ventilation have traditionally not been favoured in paediatric intensive care
61
Are spontaneous modes available in volume control ventilation?
Yes - called SIMV-VC
62
What mode of non-invasive ventilation is PEEP analogous to?
CPAP
63
How much PEEP is applied to mechanically ventilated patients in ICU?
Usually at least 4cm, even if the lungs are normal
64
What is the purpose of PEEP in mechanically ventilated patients with normal lungs?
Prevent alveolar collapse during expiration and consequent atelectasis
65
What levels of PEEP may be required in severe lung pathology?
Up to 15cm H2O
66
What can very high levels of PEEP lead to?
- Cardiovascular compromise
- CO2 retention
- Barotrauma
67
How can very high levels of PEEP lead to cardiovascular compromise?
By impeding venous return to the heart
68
When are synchronised modes of ventilation used?
During weaning
69
Why are synchronised modes of ventilation used during weaning?
To allow the patient to begin to breathe spontaneously and take over the work of breathing
70
What are synchronised modes also known as?
Support modes
71
What kind of mechanical ventilation can be provided in support modes?
Pressure or volume support
72
What happens in PS support modes?
Each spontaneous breath is augmented with a preset positive pressure
73
What happens when pressure or volume support is combined with SIMV?
Support is provided when the patient takes a spontaneous breath above the set SIMV rate
74
What is VALI?
A lung injury caused by high pressure (barotrauma) or high volume (volutrauma) ventilation
75
How can VALI be limited?
Ensuring TV is 6-8ml/kg, and PIP is <35cm H2O
76
What approach to carbon dioxide can allow ventilation to be minimised?
Permissive hypercapnia
77
What happens in permissive hypercapnia?
An arterial pH of >7.25 is aimed for, rather than a specific CO2 target
78
Why should oxygen be carefully titrated?
Because high levels of inspired oxygen be be toxic
79
What SpO2 is aimed for in mechanical ventilation?
No higher than 92%, unless there are special circumstances
80
What does judicious use of PEEP optimise?
Alveolar recruitment, which results in a lower FiO2
81
What does high frequency oscillatory ventilation (HFOV) deliver?
Low tidal volumes, typically around 2ml/kg, at a rate of >150 breaths per minute
82
How is the tidal volume delivered in HFOV?
By a pressure sine wave oscillating around a mean airway pressure
83
What does the tidal volume act as in HFOV?
A constant distending pressure
84
What is the effect of the constant distending pressure in HFOV?
It improves alveolar recruitment and ventilation/perfusion matching
85
What are the mechanisms of gas exchange in HFOV?
Not clear, but probably include convection and molecular diffusion
86
What is the role of HFOV?
Form of rescue ventilation, which is often used when conventional ventilation fails
87
At what values of MAP/FiO2 might FOV be beneficial?
When mean airway pressure is >16, and FiO2 Is >0.6
88
Does HFOV reduce barotrauma?
There are theoretical reasons it might, but not been proven compared to conventional ventilation
89
What is respiratory failure caused by?
Failure to ventilate or failure to oxygenate
90
What characterises respiratory failure caused by failure to ventilate?
Increased arterial CO2
91
What characterises respiratory failure caused by failure to oxygenate?
Decreased arterial oxygen tension
92
What might failure to oxygenate result from?
- Decreased alveolar oxygen tension
- Reduced oxygen diffusion capacity
- Ventilation perfusion mismatch
93
What is the treatment for respiratory failure caused by failure to ventilate?
Increase patients alveolar ventilation
94
What is the treatment for respiratory failure caused by failure to oxygenate?
Restoration and maintenance of lung volumes, using recruitment manoeuvres and increased airway pressures
95
What does arterial oxygenation depend on in conventional forms of ventilation?
FiO2 and airway pressure (PIP and PEEP)
96
What does arterial oxygenation depend on in HFOV?
FiO2 and mean airway pressure
97
What is carbon dioxide clearance dependent on in traditional ventilation?
Alveolar ventilation
98
What is alveolar ventilation dependent on?
Minute volume
99
How is minute volume calculated?
Tidal volume x respiratory rate
100
What is carbon dioxide clearance dependent on in HFOV?
Minute volume
101
What can increase minute volume in HFOV?
Increase the amplitude of the sine wave, and reducing the set frequency of the oscillatory waveform
102
What is inhaled NO?
A potent pulmonary vasodilator
103
What affect does inhaled NO have in the lungs?
It causes pulmonary arteriolar smooth muscle dilatation via a cGMP-dependent mechanism
104
Where has inhaled NO been proven to have benefit?
In the neonatal period in meconium aspiration syndrome
105
Who might benefit from inhaled NO (but no clinical trials to prove benefit)?
- Older children with severe refractory hypoxaemic respiratory failure
- May protect patients whose oxygenation might otherwise depend on potentially damaging ventilatory strategy
106
What is ECMO?
A modified form of cardiopulmonary bypass which can be used to provide respiratory or cardiovascular support
107
What happens in ECMO?
Deoxygenated blood is drained from the venous system, is heparinised and oxygenated outside the body via a membrane oxygenator, and pumped back into the body via a roller or centrifugal pump
108
Where is the blood returned to the body in ECMO?
Into the arteries in veno-arterial ECMO, or into the veins in veno-venous ECMO
109
What is the difference between veno-arterial (VA) and veno-venous (VV) echo?
VV provides respiratory support, VA provides cardiovascular and respiratory support
110
What are the main indications for ECMO?
- Severe hypoxaemic respiratory failure
- Cardiogenic shock
- Cardiac arrest
- Failure to wean from cardiopulmonary bypass after cardiac surgery
- As a bridge to either cardiac transplantation or placement of ventricular assist device
111
What are the relative contraindications to ECMO?
- Significant co-morbidities
- Age and size of patient and in neonates
- Presence of intraventricular haemorrhage
112
Why shouldn't ECMO be used in children with respiratory failure ventilated <7 days?
To avoid offering ECMO to children with irreversible lung injury who are unlikely to recover
