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EDAIC PART II > Physiology (Respiratory) > Flashcards

Physiology (Respiratory) Flashcards

(86 cards)

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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
Characteristics of the OHDC?
- Sigmoid shape
26
Factors affecting left shift of OHDC?
- Decreased temperature - Decreased 2,3-DPG - Decreased hydrogen ions - Carbonmonoxide
27
Factors affecting right shift of OHDC?
- Increased temperature - Increased 2,3-DPG - Increased hydrogen ions
28
What is P50?
- Oxygen saturation is 50% - Partial pressure of oxygen is 27mmHg
29
Forms of CO2 transport?
- Dissolved - HCO2 - Hb - Carb-amino compounds
30
What is the Haldane effect?
Deoxygenated Hb is able to carry more CO2 than Oxygenated Hb Deoxygenated is able to procuduce more carb-amino compounds than oxygenated ones
31
Characteristics of central chemoreceptors?
- Located ventral surface of medulla - Sensitive to PCO2 - Not O2 - Responds to changes in pH - Increased CO2 - Responds rapidly
32
Characteristics of peripheral chemoreceptors?
- Located in the carotid & aortic bodies - Responds to decreased PO2 - Responds to increased PCO2 & hydrogen ion - Responsible for hypoxic respiratory drive - Responds rapidly
33
Mechanism of central chemoreceptor response?
- Hyperventilation - Diffusion of CO2 out of capillaries - Decrease CSF pH
34
What is the ventilatory response to increased CO2?
- Increase in CO2 by 1mmHg will increase mV 2-3L - Central and peripheral chemoreceptors are responsible for this response
35
What is the ventilatory response to decreased O2?
- Only peripheral chemoreceptors respond - Significant with chronic hypoxia - COPD & Altitude - Magnified by increasing CO2
36
What is the Hering-breuer inflation reflex?
- Stimulation of pulmonary stretch receptors - Decreased RR - Increased expiratory time
37
What is DO2 - Oxygen delivery ?
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
Forms of oxygen transport in blood?
- Dissolved - Combined to Hb
39
What is the equation for oxygen content?
CaO2 = (Hb x 1.36 x O2 sats) + 0.003 x PaO2 1.36 = Huffner's constant
40
What is Huffner's constant?
1g of Hb can combine 1.39 ml of oxygen
41
What is the pasteur point?
The pressure of oxygen below which oxidative phosphorylation cannot occur - 1mmHg
42
What is critical DO2?
The degree if oxygen delivery below which supply is inadequate to meet demand- 4-8ml/kg/min
43
What is oxygen extraction ratio? VO2
The fraction of the delivered O2 taken up by tissue. Peripheral tissue - 0.2-0.3 Heart - 0.6
44
What are the factors increasing oxygen extraction ratio?
- Increased metabolism - Pyrexia - Shivering
45
What are the factors decreasing oxygen extraction ratio?
- Sepsis - Mixed venous oxygen saturation is usually increased due to decreased extraction
46
Oxygen cascade ?
Transport of oxygen from the atmosphere to the mitochondria
47
What are the characteristics of spirometry ?
- Uses a vitalograph - 75% of FVC expired in 1 sec = FEV1 - Volume of FEV1 = 3,375mls
48
Characteristics of obstructive pattern of spirometry?
FEV1/FVC ratio will be reduced
49
Characteristics of restrictive pattern of spirometry?
- Reduction in FVC - Doesn't affect early expiration - FEV1/FVC ratio is normal or high
50
Characteristics of a normal flow-volume loop?
- Y-axis = Flow in L/sec - X-axis = Volume - On x-axis = TLC & RV - Positive deflection = Expiration - Negative deflection = Inspiration
51
Obstructive disease in a flow-volume loop?
- 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
Restrictive disease in a flow-volume loop?
- Reduced TLC + Preserved RV - PEFR reduced - Flow rate is reduced
53
Characteristics of variable intrathoracic obstruction?
- Adequate gas flow during inspiration - Expiration exacerbates obstruction
54
Characteristics of variable extrathoracic obstruction?
- Gas flow allowed during expiration - Expiratory limb may be normal - Airway collapsed during inspiration - Reduced flow rates during inspiration - TLC & RV are unaffected
55
What is a shunt?
Areas of the lung which is perfused but not ventilated Increasing FiO2 will not increase arterial O2
56
Formula for pulmonary vascular resistance ?
PVR = MPAP - LAP/CO x 80 Unit = dyne/sec/cm
57
What are the factors affecting PVR? Increase?
- Increase arterial CO2 - Decreased pH - Decreased arterial PO2 - Adrenaline / Nor-adrenaline - Thromboxane-A2 - Angiotensin-II - Serotonin - Histamine - High or low lung volumes
58
What are the factors affecting PVR? Decrease?
- Decrease arterial CO2 - Increased pH - Increase arterial O2 - Isoprenaline - Acetylcholine - Prostacyclin (Prostaglandin I2) - NO - Increased peak airway pressure - Volatile anaesthetic agent
59
West zone of the lung - Zone (1)? Collapse
PA > Pa > Pv - No blood flow - Alveolar pressure higher than arterial - Present during IPPV - Equates to alveolar dead space
60
West zone of the lung - Zone (2)? Water fall
Pa > PA > Pv - Blood flow determined by arterial and alveolar pressures
61
West zone of the lung - Zone (3)? Distention
Pa > Pv > PA - Blood flow is constant in this zone - The normal healthy lung comprises of this zone
62
West zone of the lung - Zone (4)?
- Region of reduced blood flow - Low lung volume - Resistance in extra-alveolar vessels
63
What is the value of alveolar ventilation?
4500mls/min
64
What is pulmonary arterial blood flow?
5 L/min
65
what is the standard V/Q ratio
0.9 (i.e 4500/5000)
66
Draw the V/Q graph?
- Linear decrease of V/Q
67
Lung regions in relation to V/Q mismatch?
- Higher lung regions - Ventilated but not perfused - Dead space - Lower regions perfused but not ventilated - Shunt
68
What is dead-space?
The volume of air which doesn't take part in gas exchange
69
What is anatomical dead space?
The volume of the conducting airway which doesn't contain respiratory epithelium
70
What is the extent of the anatomical dead space
Courses from the nasal cavity to generation 16 of the terminal bronchioles
71
How can we measure anatomical dead space?
Fowler's method
72
What is the volume of anatomical dead space?
2ml/kg
73
What is alveolar dead space?
The volume of alveoli which is ventilated but not perfused. Thus can't take part in gas exchange
74
What is physiological dead space?
This is the sum of anatomical and alveolar dead space
75
What is the formula for calculating physiological dead-space?
The Bohr equation Vd/Vt = PaCO2 - PeCO2 / PaCO2 Vd = Physiologic dead space Vt = Tidal volume PeCO2 = End-tidal CO2
76
Describe the fowler's method?
- 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
What is compliance?
This is the volume change per unit change in pressure - ml/cmH20
78
What are the values of lung & chest wall compliance?
150 to 200 ml/cmH2O
79
What is the value of total compliance ?
75-100 ml/cmH2O Their reciprocals are added
80
What is static compliance ?
The compliance of the lungs measured when all gas flow has ceased. This is usually higher than dynamic compliance
81
What is dynamic compliance ?
The compliance of the lungs measured during respiratory cycle when gas flow is ongoing
82
Why is static compliance higher than dynamic compliance ?
The is time for volume and pressure equilibration between the lungs and measuring system
83
Factors affecting surface tension?
- Decreased at high volumes - Decreased with fibrotic changes - Increased in emphysema - Increases compliance
84
What is resistance?
The pressure change per unit change of flow cmH2O/L
85
Draw a pressure volume loop ?
See attached image Spont -ve values on x-axis IPPV +ve value on x axis
86
Read metabolic functions of the lungs
See text book

EDAIC PART II (15 decks)

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