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EDAIC PART II > Physiology (Respiratory) > Flashcards

Physiology (Respiratory) Flashcards

1
Q

How can you measure lung volumes?

A

Using a spirometer

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2
Q

What lung volumes cannot be measured by spirometry ?

A
  • TLC
  • FRC
  • RV
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3
Q

How can FRC be measured?

A
  • Body plethysmography
  • Helium dilution
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4
Q

What is tidal volume ?

A

This is the volume of gas inhaled or exhaled during a normal resting breath

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5
Q

What is residual volume?

A

Volume of gas that remains in the lungs after maximal forced expiration

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6
Q

What is inspiratory reserve volume?

A

This is the volume of gas that can further be inspired after the end of normal tidal inhalation

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7
Q

What is expiratory reserve volume?

A

This is the volume of gas that can further be exhaled after the end of normal tidal expiration

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8
Q

What is vital capacity ?

A

This is the volume of gas that can inhaled following maximal inspiration

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9
Q

what is FRC?

A

This is the volume of gas that remains in the lungs after normal tidal expiration

This is the sum of ERV and RV

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10
Q

What are the values of lung volumes and capacities ?

A
  • TV = 500
  • IRV = 2500
  • ERV = 1500
  • FRC = 3000
  • RV = 1500
  • VC = 4500
  • TLC = 6000
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11
Q

What is the closing volume?

A

This is the volume over and above RV that remain in the lungs when the small airway begins to close.

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12
Q

What is closing capacity?

A

This is the capacity at which the small airways begin to close.

This is a sum of RV + closing volume

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13
Q

How is closing volume measured?

A

This is measured by measuring the conc of nitrogen in expired gas after a single breath of 100% oxygen

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14
Q

How is anatomical dead space measured?

A

Nitrogen wash-out test

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15
Q

How is closing capacity calculated?

A

This is by adding the value of Nitrogen wash-out to RV which has been calculated by Helium dilution

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16
Q

Characteristics of closing capacity?

A
  • Increases with age
  • Reaches standing FRC at 70yo
  • Reaches supine FRC at 40 yo
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17
Q

Characteristics of hyperventilation?

Respiratory changes?

A
  • Increases arterial oxygen tension
  • Decreases arterial CO2 tension
  • Alkalosis
  • OHDC shifts to the left
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18
Q

Characteristics of hyperventilation?

Metabolic changes ?

A
  • Hypokalaemia
  • Hypocalcaemia
  • Decreased bicarbonate
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19
Q

Consequences of left shift of OHDC?

A
  • Tissue hypoxia
  • Increased affinity of Hb for oxygen
  • Reduced unloading of oxygen
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20
Q

Characteristics of hyperventilation?

Cardiovascular?

A
  • Increased O2
  • Decreased CO2
  • Electrolyte imbalance & Arrhythmias
  • Increased SVR
  • Decreased CO
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21
Q

Characteristics of hyperventilation?

CNS?

A
  • Reduced CBF- Hypocapnia
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22
Q

Characteristics of hyperventilation?

Others?

A
  • Reduced renal blood flow
  • Reduced hepatic blood flow
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23
Q

What is the alveolar gas equation ?

A

The alveolar O2 tension is equal to the inspired O2 tension minus alveolar CO2 divided by respiratory quotient.

PAO2 = PiO2 - PACO2 / RQ

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24
Q

What is RQ?

A

The amount of CO2 produced divided by the amount of O2 consumed.

It is normally 0.8 and can reach 1 in exercise

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25
Q

Characteristics of the OHDC?

A
  • Sigmoid shape
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26
Q

Factors affecting left shift of OHDC?

A
  • Decreased temperature
  • Decreased 2,3-DPG
  • Decreased hydrogen ions
  • Carbonmonoxide
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27
Q

Factors affecting right shift of OHDC?

A
  • Increased temperature
  • Increased 2,3-DPG
  • Increased hydrogen ions
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28
Q

What is P50?

A
  • Oxygen saturation is 50%
  • Partial pressure of oxygen is 27mmHg
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29
Q

Forms of CO2 transport?

A
  • Dissolved - HCO2
  • Hb - Carb-amino compounds
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30
Q

What is the Haldane effect?

A

Deoxygenated Hb is able to carry more CO2 than Oxygenated Hb

Deoxygenated is able to procuduce more carb-amino compounds than oxygenated ones

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31
Q

Characteristics of central chemoreceptors?

A
  • Located ventral surface of medulla
  • Sensitive to PCO2 - Not O2
  • Responds to changes in pH - Increased CO2
  • Responds rapidly
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32
Q

Characteristics of peripheral chemoreceptors?

A
  • Located in the carotid & aortic bodies
  • Responds to decreased PO2
  • Responds to increased PCO2 & hydrogen ion
  • Responsible for hypoxic respiratory drive
  • Responds rapidly
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33
Q

Mechanism of central chemoreceptor response?

A
  • Hyperventilation
  • Diffusion of CO2 out of capillaries
  • Decrease CSF pH
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34
Q

What is the ventilatory response to increased CO2?

A
  • Increase in CO2 by 1mmHg will increase mV 2-3L
  • Central and peripheral chemoreceptors are responsible for this response
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35
Q

What is the ventilatory response to decreased O2?

A
  • Only peripheral chemoreceptors respond
  • Significant with chronic hypoxia - COPD & Altitude
  • Magnified by increasing CO2
36
Q

What is the Hering-breuer inflation reflex?

A
  • Stimulation of pulmonary stretch receptors
  • Decreased RR
  • Increased expiratory time
37
Q

What is DO2 - Oxygen delivery ?

A

The volume of oxygen delivered to tissue per unit time.

DO2 = CO x CaO2 x 10

CO = L/min
CaO2 = Oxygen content of arterial blood ml/dl - Multiply by 10 to change the value of L/min & ml/dl

38
Q

Forms of oxygen transport in blood?

A
  • Dissolved
  • Combined to Hb
39
Q

What is the equation for oxygen content?

A

CaO2 = (Hb x 1.36 x O2 sats) + 0.003 x PaO2

1.36 = Huffner’s constant

40
Q

What is Huffner’s constant?

A

1g of Hb can combine 1.39 ml of oxygen

41
Q

What is the pasteur point?

A

The pressure of oxygen below which oxidative phosphorylation cannot occur - 1mmHg

42
Q

What is critical DO2?

A

The degree if oxygen delivery below which supply is inadequate to meet demand- 4-8ml/kg/min

43
Q

What is oxygen extraction ratio? VO2

A

The fraction of the delivered O2 taken up by tissue.

Peripheral tissue - 0.2-0.3
Heart - 0.6

44
Q

What are the factors increasing oxygen extraction ratio?

A
  • Increased metabolism
  • Pyrexia
  • Shivering
45
Q

What are the factors decreasing oxygen extraction ratio?

A
  • Sepsis
  • Mixed venous oxygen saturation is usually increased due to decreased extraction
46
Q

Oxygen cascade ?

A

Transport of oxygen from the atmosphere to the mitochondria

47
Q

What are the characteristics of spirometry ?

A
  • Uses a vitalograph
  • 75% of FVC expired in 1 sec = FEV1
  • Volume of FEV1 = 3,375mls
48
Q

Characteristics of obstructive pattern of spirometry?

A

FEV1/FVC ratio will be reduced

49
Q

Characteristics of restrictive pattern of spirometry?

A
  • Reduction in FVC
  • Doesn’t affect early expiration
  • FEV1/FVC ratio is normal or high
50
Q

Characteristics of a normal flow-volume loop?

A
  • Y-axis = Flow in L/sec
  • X-axis = Volume
  • On x-axis = TLC & RV
  • Positive deflection = Expiration
  • Negative deflection = Inspiration
51
Q

Obstructive disease in a flow-volume loop?

A
  • PEFR (Peak expiratory flow rate) decreased
  • RV increased - Gas trapping
  • Decreased flow rates during expiration
  • Increased concavity of expiratory limb
  • Moved away from RV mark
52
Q

Restrictive disease in a flow-volume loop?

A
  • Reduced TLC + Preserved RV
  • PEFR reduced
  • Flow rate is reduced
53
Q

Characteristics of variable intrathoracic obstruction?

A
  • Adequate gas flow during inspiration
  • Expiration exacerbates obstruction
54
Q

Characteristics of variable extrathoracic obstruction?

A
  • Gas flow allowed during expiration
  • Expiratory limb may be normal
  • Airway collapsed during inspiration
  • Reduced flow rates during inspiration
  • TLC & RV are unaffected
55
Q

What is a shunt?

A

Areas of the lung which is perfused but not ventilated

Increasing FiO2 will not increase arterial O2

56
Q

Formula for pulmonary vascular resistance ?

A

PVR = MPAP - LAP/CO x 80

Unit = dyne/sec/cm

57
Q

What are the factors affecting PVR? Increase?

A
  • Increase arterial CO2
  • Decreased pH
  • Decreased arterial PO2
  • Adrenaline / Nor-adrenaline
  • Thromboxane-A2
  • Angiotensin-II
  • Serotonin
  • Histamine
  • High or low lung volumes
58
Q

What are the factors affecting PVR? Decrease?

A
  • Decrease arterial CO2
  • Increased pH
  • Increase arterial O2
  • Isoprenaline
  • Acetylcholine
  • Prostacyclin (Prostaglandin I2)
  • NO
  • Increased peak airway pressure
  • Volatile anaesthetic agent
59
Q

West zone of the lung - Zone (1)? Collapse

A

PA > Pa > Pv

  • No blood flow
  • Alveolar pressure higher than arterial
  • Present during IPPV
  • Equates to alveolar dead space
60
Q

West zone of the lung - Zone (2)? Water fall

A

Pa > PA > Pv

  • Blood flow determined by arterial and alveolar pressures
61
Q

West zone of the lung - Zone (3)? Distention

A

Pa > Pv > PA

  • Blood flow is constant in this zone
  • The normal healthy lung comprises of this zone
62
Q

West zone of the lung - Zone (4)?

A
  • Region of reduced blood flow
  • Low lung volume
  • Resistance in extra-alveolar vessels
63
Q

What is the value of alveolar ventilation?

A

4500mls/min

64
Q

What is pulmonary arterial blood flow?

A

5 L/min

65
Q

what is the standard V/Q ratio

A

0.9 (i.e 4500/5000)

66
Q

Draw the V/Q graph?

A
  • Linear decrease of V/Q
67
Q

Lung regions in relation to V/Q mismatch?

A
  • Higher lung regions - Ventilated but not perfused - Dead space
  • Lower regions perfused but not ventilated - Shunt
68
Q

What is dead-space?

A

The volume of air which doesn’t take part in gas exchange

69
Q

What is anatomical dead space?

A

The volume of the conducting airway which doesn’t contain respiratory epithelium

70
Q

What is the extent of the anatomical dead space

A

Courses from the nasal cavity to generation 16 of the terminal bronchioles

71
Q

How can we measure anatomical dead space?

A

Fowler’s method

72
Q

What is the volume of anatomical dead space?

A

2ml/kg

73
Q

What is alveolar dead space?

A

The volume of alveoli which is ventilated but not perfused. Thus can’t take part in gas exchange

74
Q

What is physiological dead space?

A

This is the sum of anatomical and alveolar dead space

75
Q

What is the formula for calculating physiological dead-space?

A

The Bohr equation
Vd/Vt = PaCO2 - PeCO2 / PaCO2

Vd = Physiologic dead space
Vt = Tidal volume
PeCO2 = End-tidal CO2

76
Q

Describe the fowler’s method?

A
  • Single VC breath of O2
  • Exhales through N2 analyzer
  • Dead space gas - Pure O2 passes analyzer
  • Next mixture of dead space & alveolar gas
  • Plateau reach when pure alveolar gas passes
  • At closing capacity small airways close
  • Preferential exhalation from large airway
  • Larger airway contain more N2
77
Q

What is compliance?

A

This is the volume change per unit change in pressure - ml/cmH20

78
Q

What are the values of lung & chest wall compliance?

A

150 to 200 ml/cmH2O

79
Q

What is the value of total compliance ?

A

75-100 ml/cmH2O

Their reciprocals are added

80
Q

What is static compliance ?

A

The compliance of the lungs measured when all gas flow has ceased.

This is usually higher than dynamic compliance

81
Q

What is dynamic compliance ?

A

The compliance of the lungs measured during respiratory cycle when gas flow is ongoing

82
Q

Why is static compliance higher than dynamic compliance ?

A

The is time for volume and pressure equilibration between the lungs and measuring system

83
Q

Factors affecting surface tension?

A
  • Decreased at high volumes
  • Decreased with fibrotic changes
  • Increased in emphysema
  • Increases compliance
84
Q

What is resistance?

A

The pressure change per unit change of flow

cmH2O/L

85
Q

Draw a pressure volume loop ?

A

See attached image
Spont -ve values on x-axis
IPPV +ve value on x axis

86
Q

Read metabolic functions of the lungs

A

See text book

EDAIC PART II (15 decks)

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