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HLB > Respiratory Failure > Flashcards

Respiratory Failure Flashcards

1
Q

VA

A

the amount of air entering or exiting the alveoli and participating in gas exchange each minute

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2
Q

A-a gradient

A

the difference between PAO2 and PaO2
and hence the difference between hypoxia and hypoxaemia

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3
Q

V/Q

A

ventilation divided by perfusion

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4
Q

Hypoxic Pulmonary Vasoconstriction

A

constriction of pulmonary arteries in the presence of alveolar hypoxia to re-direct blood flow from areas that are poorly ventilated to areas that are well ventilated and more oxygen rich; no point to direct blood flow to areas of poor ventilation

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5
Q

ABG Measurement

A

a sample of blood is taken from an artery, usually the radial artery as that is the most accessible artery

the sample of blood is analysed in a few minutes in an ABG Analyser

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6
Q

acute

A

sudden deterioration

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7
Q

chronic

A

gradual and usually permanent change (eg:COPD)

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8
Q

acute on chronic

A

worsening of existing abnormalities eg: infective exacerbation of COPD

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9
Q

Generally lung failure results in

A

gas exchnage failure so hpoxaemia

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10
Q

Generally pump failures results in

A

ventilatory failure so hypercapnoea

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11
Q

Type 1 respiratory failure (hypoxaemic)

A

due to disease of the lungs, which prevents adequate oxygenation of the blood

Lungs still able to excrete CO2

This results in decrease O2 but normal or lower CO2 levels

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12
Q

State the five mechanisms of hypoxaemia.

A

Hypoventilation
Low inspired oxygen FIO2
Diffusion impairment
Shunt
Ventilation/perfusion (VQ) mismatch

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13
Q

Hypoventilation causes only Type 1 respiratory failure.

True or False?

A

False

Type 1 & Type 2

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14
Q

Hypoventilation is caused by

A

inadequate alveolar ventilation resulting in low alveolar pO2 and high pCO2

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15
Q

Hypoventilation occurs when

A

respiratory drive is impaired

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16
Q

When is respiratory drive impaired? (6)

A
  • head injury
  • drugs that suppress the respiratory center (morphine)
  • respiratory muscle weakness
  • COPD
  • neuromuscular disease
  • musculoskeletal disease
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17
Q

At higher altitudes the partial pressure of inspired oxygen increases or decreases?

A

Decreases

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18
Q

Low inspired oxygen causing type 1 RF slide

A

Low inspired oxygen FIO2 results in low alveolar PO2

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19
Q

How do we manage Type 1 Rf caused by hypoventilation or low inspired oxygen?

A

Supplemental oxygen
Can be given through nasal cannula, Venturi mask, re-breathe mask, CPAP, NIV, intubation and ventilation

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20
Q

Diffusion impairment causing Type 1 RF

A

disease or damage to the basement membrane causes a reduction in the amount of oxygen that diffuses across the interstitium and this results in hypoxaemia;

normal PAO2 but reduced PaO2

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21
Q

Diffusing capacity is also called

A

Transfer Factor (TLCO/DLCO) and can be measured by using a small amount of carbon monoxide

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22
Q

What gradient is used to determine if there is a problem with diffusion in the lungs?

A

Alveolar-arterial gradient

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23
Q

Alveolar - arterial gradient equation

A
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24
Q

4 factors affecting the diffusion of gases

A
  • surface area of the basement membrane (emphysema)
  • thickness of the basement membrane (pulmonary fibrosis)
  • diffusion coefficient of the gas
  • partial pressure and gradient of the gas
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25
Q

Management of type 1 respiratory failure due to diffusion impairment

A
  • treat the underlying condition if possible
  • supplemental oxygen
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26
Q

Type 1 respiratory failure caused by shunts

A
  • pulmonary shunt
  • anatomical shunt resulting in the mixing or venous and arterial blood
  • cardiac shunt can be congenital (cyanotix heart diseaSE) and acquired
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27
Q

Pulmonary shunts

A

Passage of deoxygenated blood from the right side of the heart to the left side without participating in gas exchange in the pulmonary capillaries

Is a physiological shunt:
- consolidation eg pneumonia (poorly ventilated areas bypassed due to the principle of pulmonary vasoconstriction)
- arteriovenous malformation AVM

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28
Q

Normal V/Q

A

0.8

29
Q

Ventilation

A

Volume of gas inhaled and exhaled over a given time period (flow of oxygen into the alveoli)

30
Q

Ventilation equation

A

Alveolar ventilation rate x respiratory rate

31
Q

Alveolar respiration rate =

A

Tidal volume - alveolar dead space

32
Q

Perfusion definition and equation

A
  • refers to the total volume of blood reaching the pulmonary capillaries in a given time period

perfusion = Cardiac output = heart rate x stroke volume

33
Q

Hypoxia definition

A

inadequate level of O2 in tissues for cellular metabolism despite adequate perfusion

34
Q

Hypoxaemia definition

A

arterial oxygen level below normal which can result in hypoxia

35
Q

VE

A

the amount of air entering or exiting the lungs

36
Q

Hypoxaemia caused by shunts: anatomical shunts: 2 examples:

A
  • deoxygenated blood from the bronchial circulation goes into the pulmonary veins
  • deoxygenated blood from coronary circulation goes into the thebesian vein and into the left ventricles
  • only 2% of cardiac output
37
Q

Is ventilation equal throughout the lungs?

A

no

38
Q

Where is ventilation lowest in the lungs and why?

A
  • at the lung apex
  • because more negative intrapleural pressure and higher transpulmonary pressure causing more distending pressure on the alveoli
  • alveoli have a lower compliance at this higher volume so less airflow during inspiration
  • ventilation progressively increases moving lower down the lung
  • ventilation is highest in the lung base
39
Q

Gradient of ventilation diagram

A
40
Q

Is perfusion equal in the lungs?

A

No

41
Q

Where is perfusion lowest?

A
  • the apex lowest
  • middle sporadic
  • base of lungs has constant perfusion
41
Q

Where is perfusion lowest?

A
  • the apex lowest
  • middle sporadic
  • base of lungs has constant perfusion
41
Q

Where is perfusion lowest?

A
  • the apex lowest
  • middle sporadic
  • base of lungs has constant perfusion
42
Q

Where is perfusion lowest?

A
  • the apex lowest
  • middle sporadic
  • base of lungs has constant perfusion
43
Q

Gradient of perfusion in the lungs diagram

A
44
Q

gradient of perfusion in the lungs diagram

A
45
Q

Is ventilation greater than perfusion at the lung base?

A

no
at the base perfusion is greater than ventilation

46
Q

Is ventilation greater than perfusion at the lung apex?

A

Yes
ventilation is greater than perfusion at the lung apex

47
Q

Is ventilation greater than perfusion in the middle of the lung?

A

No
ventilation and perfusion are equal

48
Q

Lung apices are relatively over ventilated/perfused?

A

ventilated

49
Q

Lung bases are relatively over ventilated/perfused?

A

perfused

50
Q

is there V/Q mismatch in healthy lungs?

A

Yes

51
Q

In healthy lungs how is V/Q mismatch minimised?

A

By hypoxic vasoconstriction, which directs blood away from poorly ventilated areas

52
Q

Type 2 respiratory failure is

A

hypoxaemia (pO2<8kPa) and hypercapnoea (pCO2 > 6.5 kPa)

53
Q

Type 2 respiratory failure occurs due to failure of

A

ventilation, resulting in alveolar hypoventilation

54
Q

Acute type 2 respiratory failure occurs within

A

minutes to hours, renal buffering does not have time to act, so bicarbonate level remains normal and pH drops (acidosis)

55
Q

Chronic type 2 respiratory failure can develops over

A

several days to weeks to months
the kidneys excretes H2CO3 reabsorbs HCO3-, increasing HCO3- levels and slighlty lowering pH (compensation)

56
Q

Respiratory acidosis

A
  • CO2 + H2O
  • H2CO3
  • H+ + HCO3-
  • HCO3- is an important buffer ensuring acid-base homeostasis
  • type 2 respiratory failure results in hypercapnoae which leads to an increase in the amount of hydrogen ions in the blood leading to acidosis and pH drop

can be fatal

57
Q

Management of type 1 respiratory failure: hypoxaemia

A
  • treatment of the underlying condition
  • correct hypoxaemia by giving oxygen and maintain O2 saturation between 94-98%
  • intubation and ventilation
58
Q

Management of Type 2 respiratory failure: hypoxaemia and hypercapnoae:

A
  • treatment of underlying condition if possible
  • administering controlled O2 aiming to keep saturation between 88-92%
  • non-invasive intubation (NIV)
  • intubation and ventilation
59
Q

State the 4 types of hypoxia:

A
  • ctotoxic or histotoxic hypoxia
  • circulatory or stagnant hypoxia
  • anaemia hypoxia
  • hypoanaemic or hypoxic hypoxia
60
Q

Cytotoxic or Histototoxic hypoxia

A
  • reduced inability to utilise O2
  • cyanide poisoning impairs mitochondrial cytochrome oxidase
61
Q

Circulatory or Stagnant hypoxia

A
  • reduced ability to deliver O2
  • heart failure
62
Q

Anaemic hypoxia

A
  • reduced ability to deliver O2
  • CO poisoning
63
Q

Hypoanaemix or hypoxic hypoxia

A
  • reduced ability to deliver O2
  • PaO2 (reduced amount of oxygen in the blood)
64
Q

Dead space

A
  • anatomical dead space = upper respiratory tract upto 150 terminal bronchioles do not take part in gas exchange - 150ml
  • alveolar dead space = alveoli that have lost blood supply do not participate in gas exchange
  • physiological dead space = anatomical dead space + alveolar dead space
65
Q

in healthy lungs physiological dead space =

A

anatomical dead space

66
Q

Anatomical dead space function

A

humidifying air

HLB (49 decks)

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