Acute Respiratory Problems / Respiratory Failure Flashcards

(65 cards)

1
Q

What is respiratory failure?

A

When the lungs aren’t working correctly, resulting in hypoxia

there may or may not be raised levels of carbon dioxide in the blood

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2
Q

What are the main differences between type 1 and type 2 respiratory failure?

A

Type 1:

  • there is hypoxia only
  • this is focal - only one lobe / part of the lung is malfunctioning
  • there is V/Q mismatch

Type 2:

  • there is hypoxia and hypercapnia
  • this is global - affects large areas of the lungs
  • there is no global gas exchange
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3
Q

What abnormalities are shown on ABG for type 2 respiratory failure?

A
  • elevated PaCO2
  • reduced PaO2
  • elevated HCO3-
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4
Q

What condition is very frequently associated with type 2 respiratory failure?

A

COPD

look for a history of heavy smoking

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5
Q

What is represented by the boats and lorries in this diagram?

A

boats are ventilation (V) and lorries are perfusion (Q)

in order for adequate lung function, both ventilation and perfusion need to be functioning

ventilation involves getting air into the alveoli

perfusion involves getting the oxygen from the alveoli to the rest of the body

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6
Q
A
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7
Q

What is meant by ventilation (V)?

A

the volume of gas inhaled and exhaled from the lungs in a given time period, usually one minute

this involves air entering the alveoli

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8
Q

What is meant by perfusion?

A

perfusion is the total volume of blood reaching the pulmonary capillaries in a given time period

this involves getting oxygen from the alveoli to the rest of the body

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9
Q

What would the ideal V/Q ratio be?

How does V/Q ratio differ in different parts of the lung and what does this mean?

A

the ideal V/Q ratio would be 1 for maximally efficient pulmonary function

the ratio varies depending on the part of the lung concerned

when standing up straight, the ratio is roughly 3.3 in the apex of the lung and 0.63 in the base

ventilation exceeds perfusion towards the apex

perfusion exceeds ventilation towards the base

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10
Q

What is meant by V/Q mismatch?

A

a mismatch between the alveolar ventilation and the alveolar blood flow

this can arise due to either reduced ventilation of part of the lung or reduced perfusion

gas exchange in the affected alveoli is impaired, resulting in a fall in pO2 and a rise in pCO2

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11
Q

Why does pCO2 in the blood not usually rise despite V/Q mismatch?

What physiological mechanisms are in place to prevent this?

A
  • hypoxic vasoconstriction causes blood to be diverted to better ventilated parts of the lung
  • the haemoglobin in these well ventilated alveolar capillaries will already be saturated
  • RBCs will be unable to bind additional oxygen to increase the pO2
  • the pO2 of the blood remains low, which acts as a stimulus to cause hyperventilation, resulting in either normal or low CO2 levels
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12
Q

What is involved in the principles of type 1 respiratory failure relating to solubility of CO2 and O2 and compensation?

A

CO2 is much more soluble than O2

(this is why O2 needs Hb to carry it)

  • a good lung cannot hyper-oxygenate (>100% saturation)
  • a good lung can hyperventilate to remove CO2
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13
Q

What is shown in this image of Type 1 respiratory failure?

A
  • there is reduced ventilation in a part of the lung
    • oxygen is not getting into the alveoli, but perfusion is normal
  • the rest of the lung has increased ventilation to compensate
    • ​perfusion to the rest of the lung is still normal and not increased
  • the rest of the lung is at 100% capacity as it is fully oxygenating the blood
  • due to the blue region, despite compensation, there is still hypoxia as you cannot go above 100% saturation
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14
Q

How can pneumonia lead to type 1 respiratory failure?

A

in pneumonia the alveoli are filled with exudate

this impairs the delivery of air to the alveoli and lengthens the diffusion pathway for respiratory gases

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15
Q

When does type 2 respiratory failure result from V/Q mismatch?

A
  • the result of reduced ventilation / perfusion intially is hypoxia
  • the lung is still able to remove CO2, so hypercapnia does not occur unless ventilation is severely limited
  • in T2RF there is a global problem leading to complete loss of gas exchange due to malfunctioning alveoli
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16
Q

What are common causes of Type 1 respiratory failure?

A
  • acute asthma
  • atelectasis
  • pulmonary oedema
  • pneumonia
  • pneumothorax
  • pulmonary embolism
  • ARDS
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17
Q

What are common causes of type 2 respiratory failure?

A
  • acute severe asthma
  • COPD
  • upper airway obstruction
  • neuropathies (GBS, MND)
  • drugs - opiates
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18
Q

What is involved in the management of type 1 respiratory failure?

A

CPAP - continunous positive airway pressure

  • air (above atmospheric pressure) is pumped into the lungs continuously, which opens deep distal airways
  • this increases ventilation (V) so helps when there is a reduced V to an area of the lungs
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19
Q

What is involved in the management of type 2 respiratory failure?

A

BIPAP - bilevel positive airway pressure

  • there is increased airway recruitment, which increases ventilation (V)
  • in BIPAP, you receive positive air pressure on inspiration and expiration, but the air pressure is higher on inspiration
    • CPAP involves the same amount of pressure being delivered on inspiration and expiration
  • air is pumped in on inspiration, but CO2 is also sucked out on expiration
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20
Q

What is normal intrapleural pressure?

What happens if this is changed?

A

normal intrapleural pressure is from -5 to -8 cm H2O

this is a negative pressure that holds open the lungs

if it is changed (i.e. through pneumothorax) then ventilation cannot occur as effectively

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21
Q

What is a pneumothorax?

A

air within the pleural space

this air pushes on the outside of lung and makes it collapse

this could involve the collapse of entire lung or only a portion of the lung

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22
Q

What is the difference between a primary and a secondary pneumothorax?

A

Primary pneumothorax:

  • this occurs spontaneously without an apparent cause and in the absence of significant lung disease

Secondary pneumothorax:

  • this occurs in the presence of existing lung disease
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23
Q

What type of person is more likely to get a primary spontaneous pneumothorax?

How does it develop?

A

this is more likely to occur in a young, healthy person who does not have any significant lung disease

a bleb (lump in the pleura) bursts open, leading to air entering the pleural space

this is random and spontaneous

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24
Q

What are the risk factors that increase the likelihood of primary pneumothorax?

A
  • men are more likely to get pneumothoraces than women
  • smoking
  • Marfanoid habitus
    • really tall individuals with elongated limbs & hypermobility of joints
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25
Who is more likely to get a secondary pneumothorax?
* patients with a **smoking history** * patients are usually **_over 50_** with **_lung disease already diagnosed_** * this would include **younger patients with cystic fibrosis**
26
How does secondary pneumothorax occur in someone with emphysema?
the alveolar bullae in emphysema can burst, allowing air to rush into the pleural space
27
What happens in a tension pneumothorax?
a **_one-way valve_** is formed * with each **inspiration**, some air is pumped **into the pleural space** * upon **expiration**, the **_air cannot leave_** the pleural space * with every breath, **more air enters the pleural space** and the **_pneumothorax gets bigger_**
28
What are the signs and symptoms of tension pneumothorax?
***_Due to lung compression:_*** * severe **dyspnoea** * **tracheal deviation** (away from the lesion) * **_silent_ chest** with **_hyperresonance_** and **_reduced expansion_** on lesioned side ***_Due to mediastinal shift:_*** * hypotension * tachycardia
29
How does someone die from a tension pneumothorax?
death from tension pneumothorax is **cardiac**, rather than respiratory * the pneumothorax becomes so large that it presses against the **_vena cava_** in the mediastinum * this leads to a **loss of venous return** and **_circulatory collapse_** * **_tachycardia_** is present to try and **compensate for the hypotension**
30
Which direction does the trachea deviate in tension pneumothorax?
as the tension pneumothorax balloons, it will **push the trachea away from itself** the trachea **_deviates AWAY_** from the side of the pneumothorax
31
What does the chest sound like in a tension pneumothorax?
the chest sounds **_silent_** it is **_hyperresonant_** due it just being **air** present in this region and **no lung tissue**
32
What is the management for tension pneumothorax?
**_large bore cannula_** in the **_2nd intercostal space_** **_midclavicular line_** this is an **orange** or **grey** cannula this needs to be inserted **just above the 3rd rib** to avoid the neurovascular bundle resting underneath the ribs
33
How are other pneumothoraces (not tension pneumothoraces) managed?
**_chest drain_** or **_needle aspiration_** this needs to be inserted in the **safe triangle** this is in the **2nd intercostal space**, **midclavicular line** using a **sterile** technique
34
What are the stages involved in the pneumothorax treatment algorithm?
if the patient is **_symptomatic_** (**breathless**) or the pneumothorax is **_\>2cm_** then management is different large or symptomatic secondary pneumothorax - go straight for the chest drain regardless of the size of the pneumothorax, if the patient is **_symptomatic_** then **_different management_** needs to be taken
35
**D - needle aspiration and give O2** the pneumothorax is primary and less than 2cm however, the patient is symptomatic (breathless) so needle aspiration is performed if this is not successful, then a chest drain would be performed
36
What is a pulmonary embolism? Where does it originate from?
PE tends to come from a **_VTE_** - a clot that forms elsewhere in the body these tend to be **_DVTs_** that occur in the **deep veins of the calves** this is because the **compliance is massive** and the **pressure is low** here
37
What are the stages involved in a PE developing from a thrombus?
a small part of the thrombus breaks off and drains into the **inferior vena cava** this enters the **right side of the heart** and into the **pulmonary artery**, to become lodged in the lungs
38
What are the 3 different types of PE?
* **acute massive PE** * **acute submassive** & **small PE** * **chronic PE**
39
What is an acute massive PE and what are the typical symptoms?
this involves **_sudden complete occlusion_** of the pulmonary artery this results in: * ***collapse*** * ***central crushing chest pain*** * ***severe dyspnoea***
40
What is an acute submassive & small PE? What are the typical symptoms?
**_sudden incomplete occlusion_** of pulmonary artery or distal artery this results in: * ***pleuritic chest pain*** * ***haemoptysis*** * ***dyspnoea***
41
What is a chronic PE? What symptoms does this present with?
this involves chronic occlusion of **_pulmonary microvasculature_** this results in ***exertional dyspnoea***
42
What might be seen on CXR for someone with PE?
* classical **S1Q3T3 pattern** * right axis deviation * right bundle branch block * sinus tachycardia
43
What is meant by S1Q3T3 pattern on ECG?
* **big S wave** in lead 1 * **pathological Q wave** in lead 3 * **inverted T wave** in lead 3 * this is a sign of **_right heart strain_** * right side strain is increased to try and **overcome the obstruction** in the pulmonary vasculature
44
What sign might be seen on CXR for pulmonary embolism?
CXR can show **_Westermark's sign_**, which has a high positive predictive value it is a finding of **oligaemia (increased translucency)** distal to a large vessel that is occluded by a PE
45
What mnemonic is used to remember the risk factors for PE?
CT, s'il vous plait WHY - because you will be asking the radiologist for a CTPA
46
What does C stand for in the mnemonic CT s'il vous plait?
* cancer * chemotherapy * cardiac failure * COPD * Factor C deficiency
47
What does T stand for in the mnemonic CT s'il vous plait?
* trauma * time (age) * thrombocytosis
48
What does S stand for in the mnemonic CT s'il vous plait?
* stasis * surgery * Factor S deficiency
49
What does V stand for in the mnemonic CT s'il vous plait?
* **varicose veins** * **virchow's triad** (3 factors important in development of venous thrombosis) * stasis of blood flow * endothelial injury * hypercoagulability * **Factor V Leiden**
50
What does P stand for in the mnemonic CT s'il vous plait?
* pill (OCP) * pregnancy * puerperium (period of 6 weeks after childbirth) * previous VTE * polycythaemia * paraprotein deposition
51
What are the NICE guidelines for preventing VTE? How can the mechanisms for preventing VTE be remembered?
* everyone must be VTE risk assessed **_within 24 hours_** of hospital admission * mechanical prevention involves **_anti-embolic stockings_** (TED stockings) * pharmacological prevention involves **_low-molecular-weight-heparin_** (**tinzaparin**) * this can be remembered as **_"TEDs & Tinz"_**
52
What score is used to stratify PEs?
the **_Well's score_** * a **_score \<4_** is a **low-risk PE** and a **_D-dimer test_** is done * a score of **_4 or more_** is a **high-risk PE** and **_CTPA_** is done
53
What factors are scored in the Well's score? What mnemonic is used to remember this?
can be remembered using "PE SCORE" * P - previous DVT / PE * E - evidence of DVT * S - stasis * C - cancer * O - opinion is PE * R - rate raised (\>100) * E - exsanguination (haemoptysis)
54
What question must be asked before deciding how to manage a patient with PE?
are they **_haemodynamically stable_**? i. e. systolic blood pressure **_\< 90_** * if **YES** then this is a **submassive/small PE** * if **NO** then this is a **massive PE**
55
What is the treatment for submassive/small PE?
* **respiratory support** * **anticoagulation** * the aim of the treatment is not to eradicate the PE that is already present, but to **_prevent further PEs_**
56
What type of anticoagulation is used to treat a submassive / small PE?
* **_Fondaparinux / Heparin_** is given for **5 days** * this is "bridging warfarin" * warfarin takes a **few days to take effect** clinically and is a **procoagulant** in the acute phase, so heparin needs to be given to bridge this effect * **_Warfarin_** is then given for **3 months** * a **_DOAC (e.g. dobigatran)_** is also started
57
What are the treatments for someone presenting with a massive PE (not haemodynamically stable)?
* respiratory support * 1st line treatment is **_thrombolysis_** with a clot-busting drug * 2nd line treatment is **_embolectomy_**
58
What type of drugs are used for thrombolysis? Why are they not used to treat a submassive/small PE?
**_IV thrombolytics (fibrinolytics)_** such as **alteplase** and **streptokinase** these have risks associated with them, and the risks outweight the benefits for small/submassive PE
59
What is the definition of ARDS?
ARDS is a form of **_hypoxaemic acute lung injury_** it is a **_non-cardiogenic pulmonary oedema_** (i.e. pulmonary oedema occurring due to an immune reaction) it is a type of **respiratory failure** characterised by **rapid onset** of **widespread inflammation** in the lungs
60
What are the common causes of ARDS? In what type of patient is it particularly common?
* drugs * ventilation * nearly drowning * severe burns * sepsis * pneumonia * transfusion reactions it is particularly common in critically ill (ITU) patients
61
How does ARDS lead to alveolar collapse and shunt?
* the body responds to the cause with a profound **inflammatory response** * this increases **vascular permeability** and allows fluid into the lungs, resulting in **_pulmonary oedema_** * **fluid in the alveoli** weighs on the alveoli and **ruins their _structure_ and _integrity_** * this leads to **_alveolar collapse_** and **_diffuse alveolar damage_** * fluid leaks into the **space between the capillary and the alveolus**, increasing this space * this leads to a **_shunt_** in **50%** of the alveoli
62
What criteria is used to define ARDS?
the **_Berlin criteria_**, which can be simplified to: * **_A_** - alternative cause (i.e. not cardiogenic pulmonary oedema) * **_R_** - rapid onset (\< 1 week) * **_D_** - dyspnoea * **_S_** - similar on CXR
63
What are the 3 main symptoms of ARDS?
* **dyspnoea** (shortness of breath) * bluish discolouration of the skin (**cyanosis**) * **tachypnoea** (rapid breathing)
64
What are the investigations performed for ARDS?
* **arterial blood gas (ABG)** * **CXR / CT** * **Echocardiogram** * **Covid swab** - COVID-19 has been seen to cause ARDS it is important to treat the underlying cause and be aware that it exists
65
**A - apixaban** * the patient is **haemodynamically stable** as **_SBP \> 90_** * alteplase should not be given as thrombolysis is not in the patient's best interest at this stage * a **DOAC**, such as **apixaban**, should be given