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Year 1 HLB Respiratory > Respiratory Failure > Flashcards

Respiratory Failure Flashcards

(93 cards)

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1
Q

What is respiratory failure?

A
  • inability to maintain gas exchange
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2
Q

In respiratory failure type 1, what happens to PaO2 and PaCO2?

A
  • hypoxaemia (low O2 in blood)
  • <8.0kPA or <60mmHg
  • normal CO2
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3
Q

What is hypoxaemia?

A
  • blood oxygen is low
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4
Q

What is hypoxia?

A
  • low O2 supply to tissue
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5
Q

What is hypocapnia?

A
  • low CO2 - <4.5kPA or <33.8mmHg
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6
Q

What is hypercapnia?

A
  • high CO2
  • >6.0kPA or >45mmHg
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7
Q

Why does CO2 remain normal in type 1 respiratory failre?

A
  • damaged lungs are sufficient to expire CO2
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8
Q

What is the main problem with the lungs in type 1 respiratory failure?

A
  • damage to lung tissue
  • lungs unable to facilitate gas exchange
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9
Q

What is ventilation/perfusion in the lungs?

A
  • ratio between ventilation and perfusion across alveoli and capillaries
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10
Q

In type 1 respiratory failure, why is there ventilation/perfusion mismatch?

A
  • ventilation is sufficient
  • perfusion is low causing ⬇️ O2
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11
Q

Is blood flow to the lungs affected in type 1 respiratory failure?

A
  • generally no
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12
Q

In respiratory failure type 2 what happens to PaO2 and PaCO2?

A

1 - hypoxaemia

  • PaO2 = <8.0kPA or <60mmHg

2 - hypercapnia

  • PaCO2 = >6.0kPA or 45mmHg
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13
Q

What is the main problem in the lungs causing type 2 respiratory failure?

A
  • ⬇️ ventilation, generally affects whole lung
  • inability to overcome ⬆️ resistance to ventilation
  • generally caused by ⬇️ compliance and/or ⬆️ elasticity
  • CO2 cannot be removed from blood
  • O2 cannot reach the blood for gas exchange
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14
Q

What happens to patients breathing in type 2 respiratory failure?

A
  • hypoventilation with short shallow breathes
  • insufficient for normal function
  • low O2 enters and CO2 not removed effectively
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15
Q

In acute type 2 respiratory failure, is renal function able to maintain homeostasis?

A
  • no
  • kidneys are slow to react
  • retention of HCO3- is too slow to buffer ⬆️ CO2
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16
Q

What generally happens to pH in acute and chronic 2 respiratory failure?

A
  • pH ⬇️
  • ⬆️ CO2 = ⬆️ carbonic acid and ⬆️ H+
  • HCO3- is insufficient to ⬆️ pH
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17
Q

How quickly can acute type 2 respiratory failure commence?

A
  • minutes to hours
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18
Q

In chronic type 2 respiratory failure, is renal function able to maintain homeostasis?

A
  • partially
  • kidneys excrete carbonic acid H2CO3
  • kidneys retain HCO3-
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19
Q

What generally happens to pH in chronic type 2 respiratory failure?

A
  • HCO3- retention ⬆️ pH slightly
  • not to normal pH though
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20
Q

What is a restrictive lung disease?

A
  • compliance is ⬇️
  • elasticity is ⬆️
  • lungs struggle to inflate and ventilation is ⬇️
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21
Q

What is a obstructive lung disease?

A
  • compliance is ⬆️
  • elasticity is ⬇️
  • lungs are able to inflate but not recoil
  • CO2 is ⬆️ and O2 is ⬇️
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22
Q

What is stagnant hypoxia?

A
  • blood flow is slow
  • ⬇️ blood supply to tissues
  • O2 levels in the blood are normal
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23
Q

What is histotoxic/cytotoxic hypoxia?

A
  • ⬇️ or no O2 absorbed from blood
  • caused by tissue poisoning
  • ⬇️ blood supply to tissues
  • O2 levels in the blood are normal
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24
Q

What is anaemic hypoxia?

A
  • ⬇️ haemoglobulin binding to blood
  • ⬇️ O2 delivered to tissue
  • CO could cause this, inhibiting O2 binding
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25
What is hypoxaemia?
- low level of O2 in arterial blood
26
What are the 5 mechanisms that can hypoxaemia?
1 - hypoventilation 2 - ⬇️ fraction of O2 (FiO2) in the air 3 - diffusion impairment 4 - shunt 5 - V/Q mismatch
27
What is hypoventilation?
- slow and shallow breathing - ⬇️ ventilation and perfusion = low O2 - insufficient O2 arterial blood
28
Following hypoventilation, what happens to oxyhemoglobin saturation, measured by pulse oximetry?
- ⬇️ oxyhemoglobin or ⬇️ SaO2
29
During hypoventilation what happens to CO2 levels?
- CO2 can ⬆️ - CO2 cannot be removed from lungs sufficiently
30
What is the Alveolar/arterial gradient (A-a)?
- measure of arterial (A) and alveolar blood concentration of O2
31
What does the big and little a mean in Alveolar/arterial gradient?
- A = alveolar 2 concentration - a = arterial concentration
32
In the Alveolar/arterial gradient (A-a), what should the difference be between O2 in the alveolar and arterial blood flow?
- ideally the same same as O2 defuses from alveolar to arteries - normal difference is 5-15mmHg
33
What does FiO2 mean?
- fraction of O2 in inspired air
34
What is normal partial pressure of atmospheric air at sea level?
- 760mmHg - written as Patm
35
What does Ph2O mean in the Alveolar/arterial gradient (A-a) formula?
- partial pressure lost to water in upper respiratory tract - water dilutes gases
36
At normally body temperature, what is the partial pressure of air lost to water vapour in the upper respiratory tract?
- 47mmHg
37
What does R mean in the Alveolar/arterial gradient (A-a) formula?
- respiratory quotient - respiratory exchange ratio - ratio between O2 and CO2 of expired air
38
The R in the Alveolar/arterial gradient (A-a) relates to the ratio between O2 and CO2 in expired air, why is this useful?
- provides information about metabolism - \<1 = carbohydrates - 0.9 = proteins - 0.7 = fats
39
What is the normal value in the western world used for R in the Alveolar/arterial gradient (A-a) formula?
- 0.8
40
What is the Alveolar/arterial gradient (A-a) formula?
- PAO2 = FiO2 x (Patm-Ph20) - (PaCO2/R) - PaO2 - PAO2 - standard values = 0.21 x (760-47) - (PaCO2/0.8) - PaO2 - standard values can be affected by disease, altitude etc...
41
How do you acquire PaO2 for the Alveolar/arterial gradient (A-a)?
- value is taken from arterial blood gas
42
Why does partial pressure of gas decrease at altitude?
- gas molecules spread out - Boyles law = ⬆️ volume = ⬇️ pressure - Boyles law = ⬇️ volume = ⬆️ pressure
43
If at high altitude where pressure is lower, what can happen to the Alveolar/arterial gradient (A-a)?
- it will not balance
44
If at high altitude where pressure is lower, and the Alveolar/arterial gradient (A-a) is offset, patients suffer with altitude sickness, such as nausea, headaches, tiredness, loss of appetite etc..., how would you treat this immediately?
- give patients 80% gas
45
What is impaired diffusion?
- inability to facilitate gas exchange at alveolar/capillaries
46
What is the most common cause of impaired diffusion?
- blockage of interstitial space (0.5um) - space between alveolar and capillaries
47
Why could exercise cause impaired diffusion?
- speed of blood is ⬆️ due to increased cardiac output - ⬇️ time allowed for diffusion
48
Why could pulmonary fibrosis cause impaired diffusion?
- fibrosis causes thickening of alveoli - thickening of alveoli ⬇️ surface area ⬇️ perfusion - fibrosis may block the alveoli all together due a ⬇️ in parenchyme tissue
49
In patients with impaired diffusion, is high flowing O2 (80-90%) able to help?
- yes - forces O2 in alveoli and ⬆️ perfusion
50
What is a continuous positive airway pressure (CPAP) machine?
- machine that applies continuous pressure with ⬆️ O2 - ensures respiratory tract remains open - ⬆️ diffusion
51
What is shunting?
- blood may not reach alveoli and be oxygenated - capillaries may reach alveoli but and low O2 perfusion occurs - capillaries do not reach alveoli and no O2 saturation - essentially O2 and CO2 rich blood can mix, causing a reduction in SaO2
52
What happens to O2 saturation where shunting has occured?
- SaO2 ⬇️ - oxygenated blood mixes with non oxygenated blood
53
What is airspace shunting?
- pressure in part of lung is high meaning O2 will not move down the partial pressure gradient - can occur in pneumothorax
54
What is an example of airspace shunting?
- pneumothorax - increased pressure on part of the lung
55
What is vasculature shunting?
- blood vessels do not reach the alveoli - blood is not oxygenated
56
What is heart shunting?
- blood crosses from right to left side of the heart - oxygenation of blood is ⬇️
57
Can shunting be treated with ⬆️ O2 gases?
- generally no - helps confirm diagnosis as a form of shunting
58
What is ventilation/perfusion (V/Q) mismatch?
- mismatch between ventilation (V) and perfusion (Q) - most common cause of hypoxia
59
Is ventilation/perfusion equal throughout the lungs?
- no - gravity contributes
60
Where is ventilation highest in the lungs?
- at the apex - lowest at the base
61
Where is perfusion highest in the lungs?
- base of the lungs - lowest at apex
62
What is dead space in the respiratory tract?
- air in lungs that does not take part in perfusion
63
What are some common diseases that can cause ventilation/perfusion (V/Q) mismatch?
- pulmonary embolism - COPD - pneumonia
64
Will air help patients with a high ventilation/perfusion (V/Q) mismatch?
- yes - ⬆️ in perfusion
65
How do we quantify ventilation?
- amount of air inhaled that reaches the alveoli during 1 minute - measured in L/min
66
How do we calculate ventilation?
- alveolar ventilation rate (AVR) x respiratory rate (RR) - AVR = tidal volume - alveolar dead space - ventilation = (AVR - dead space) x RR
67
What are the normal values for tidal volume, respiratory rate and dead space at rest?
- tidal volume = 500ml - deadspace = 150ml - respiratory rate = 12 breaths/minute
68
Using the values below, what would ventilation be at rest? - tidal volume = 500ml - deadspace = 150ml - respiratory rate = 12 breaths/minute
- ventilation (V) = (AVR - dead space) x RR - V = (500-150) x 12 = 4200ml/min - this can ⬆️ significantly during exercise
69
What is perfusion and what can we use to calculate it?
- perfusion is the amount of blood reaching the capillaries at a given time - cardiac output is used to determine this
70
What is a normal cardiac output at rest?
- 5000ml/min or 5L - 5000 ml of blood reaches the capillaries/minute
71
If we know a ventilation at rest is approx 4200ml and a cardiac output is 5000ml, what is the ventilation/perfusion?
- ventilation/perfusion - 4200 / 5000 = 0.84 - normal V/Q is 0.8
72
What are the 3 things that drive ventilation and perfusion of the lungs?
1 - gravity 2 - pleural pressure 3 - compliance and elasticity
73
Clinically what does ventilation/perfusion mismatch lead to in the blood?
- ⬇️ O2 saturation
74
Generally, pneumonia (an infection) will reduce surface area of alveoli and destroy the alveoli altogether. Will this mainly affect ventilation or perfusion?
- pneumonia infection causes damage throughout the lungs - this can reduce ventilation - ⬇️ surface area due to damaged alveoli - pus can block alveoli altogether
75
A pulmonary embolism (blood clot) can block blood flow to part of the lungs, is this likely to affect ventilation of perfusion?
- perfusion as no blood is available to perfuse with - ventilation continues as normal
76
Where is the largest proportion of dead space in the respiratory tract?
- upper respiratory tract - conducting zone - mouth, pharynx, larynx and bronchi
77
In dead space there is high ventilation, but is any perfusion able to occur?
- no - wasted air
78
In type 1 respiratory failure, is the cause generally due to damaged lung tissue or V/Q mismatch?
- damage to lung tissue - damage to alveoli means air arrives but cannot perfuse - which can lead to V/Q mismatch
79
What is the definition, according to O2 levels of type 1 respiratory failure?
- O2 \<8kPA or 60mmHg - hypoxaemia
80
In type 1 respiratory failure, what are the 2 things that can happen to CO2 levels?
- CO2 can ⬆️ - CO2 can remain normal
81
In type 2 respiratory failure, is the cause generally due to damaged lung tissue or V/Q mismatch?
- V/Q mismatch - ⬇️ removal of CO2 from blood
82
In type 2 respiratory failure, why can CO2 not diffuse across the capillary/alveoli efficiently?
- ⬇️ ventilation effort - ⬆️ resistance to ventilation so CO2 cannot leave lungs due to partial pressure gradients
83
What is the definition, according to CO2 and O2 levels of type 2 respiratory failure?
- CO2 \>6.5kPA or 50mmHg = hypercapnia - O2 \<8kPA or 60mmHg (can be normal as well) = hypoxaemia
84
Asthma is a form of type 1 respiratory failure, what is an effective way to treat this?
- provide a bronchodilator - ⬆️ ventilation
85
Asthma is a form of type 1 respiratory failure, what is the aim when treating this?
- return SaO2 to normal levels - normal SaO2 = 94 - 98%
86
COPD is a form of type 2 respiratory failure, what is the aim when treating this?
- return SaO2 to good levels - CANNOT CURE - normal SaO2 = 88 - 92% - these SaO2 levels are likely to be normal for them
87
What is an example of non-invasive ventilation?
- nasal cannula or simple mask - both provide ⬆️ O2
88
In patients who are extremely hypoxic, will basic masks or nasal cannulas be sufficient to treat these patients?
- generally no - use continuous positive airway pressure (CPAP)
89
If masks and CPAP are insufficient in patients with type 2 respiratory failure, what else can be used in really hypoxic patients?
- intubation and ventilation
90
What is intubation?
- tube is inserted into patients throat - acts as patients respiratory tract - commonly called tracheal intubation
91
What is assisted ventilation?
- patients are attached to a respiratory machine - essentially breathes for the patient
92
What is physiological and pathological dead space in the lungs?
- physiological = normal parts of lungs where gas exchange does not take place - pathological = part of lung normally involved in gas exchange is damaged and unable to be involved in gas exchange
93
What is a portal blood system?
- blood flows from one capillary bed into another - blood flows between veins and not straight back to heart - characteristic of blood is de-oxygenated

Year 1 HLB Respiratory (25 decks)

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