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Generals G.O.A.T > Respiratory > Flashcards

Respiratory Flashcards

1
Q

What does a right shift of the Hb-oxygen dissociation curve mean?
What causes it?

A

Shifting to the right means increased unloading of oxygen to the tissues

Seen with acidosis, increased PCO2 (hypercarbia), increased temp (heat) and increased 2,3 DPG in RBC

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2
Q

What does a left shift of the Hb-oxygen dissociation curve mean?
What causes it?

A

Shifting to the left means decreased unloading of oxygen to the tissues
Alkalosis, hypothermia

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3
Q

How does the O2-hemoglobin curve shift in acidemia

A

Right

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4
Q

How does the O2-hemoglobin curve shift with increased CO2 concentrations?

A

Right

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5
Q

How does the O2-hemoglobin curve shift in decreased temperatures?

A

Left

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6
Q

How does the O2-hemoglobin curve shift in increased 2,3-DPG?

A

Right

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7
Q

What is the Bohr effect?

A

Increased CO2 and H+ → decreases affinity of Hb for O2 and promotes offloading

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8
Q

What forms does CO2 exist in the blood?

A
  1. HCO3 - most
  2. Carbamino compounds
  3. Dissolved in plasma
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9
Q

What is the Haldane effect?

A

Dexoygenated haemoglobin is better at carrying CO2

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10
Q

What is the difference between the Bohr and Haldane effects?

A
  1. Bohr → increase in CO2 (or H+) in blood causes O2 to be displaced from haemoglobin (tissues)
  2. Haldane → binding of O2 with hemoglobin causes CO2 to be displaced from the hemoglobin (lungs)
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11
Q

Where are the peripheral chemoreceptors?

A

Aortic and carotid bodies

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12
Q

Where are the central chemoreceptors located?

A

The respiratory centre in the medulla and the pons

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13
Q

How do the central chemoreceptors work?

A

Respond to increasing H+ by increasing ventilation

H+ cannot cross BBB

CO2 in the blood rises, diffuses in to CSF, and Hydrogen ions dissociate

Not influenced by PO2

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14
Q

Parasympathetic stimuation (ACh) causes what effect in the lung?

A

BronchoCONSTRICTION

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15
Q

Sympathetic stimualtion (Epi/Norepi) causes what effect in the lung?
Via which receptor?

A

BronchoDILATION
B2 adrenergic receptors

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16
Q

What compose the conducting airways?

A

Trachea and bronchi

*Anatomic dead space

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17
Q

What cells secrete secrete surfactant?

A

Type II alveolar epithelial cell

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18
Q

Which alveolar epithelial cells are most abundant?

A

Type 1 - 95%

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19
Q

What are the roles of type 2 alveolar epithelial cells

A
  1. Stem cells from which type 1 cells arise
  2. Produce/Store surfactant
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20
Q

What is surfactant composed of?

A

80% phospholipids (contains DPPC)
20% neutral lipids and proteins

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21
Q

What muscle(s) plays a role in the process of inspiration?

A
  1. Diaphragm → contracts and flattens, causes intrapleural space to become more negative
  2. External intercostals → make diaphragm contraction more efficient, greater role during exercise
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22
Q

What muscle(s) plays a role in the process of expiration?

A
  • Typically a passive process
    1. Abdominal muscles push diaphragm up → increase the intrapleural pressure
    2. Internal intercostals → oppose action of external intercostals, pull ribcage down and in
    3. Accessory muscles → laryngeal muscles, act as “breaks”
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23
Q

What components determine lung compliance?

A
  1. Elastic forces of the lung → elastin and collagen fibers
  2. Surface tension of the alveoli mediated by surfactant
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24
Q

What is tidal volume?

A

Volume of air inspired or expired with each normal breath

10-15 ml/kg

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25
Q

What is the inspiratory reserve volume?

A

The extra volume of air that can be inspired OVER the normal tidal volume

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26
Q

What is the inspiratory capacity?

A

Tidal volume + inspiratory reserve volume

The total amount of air that an individual can breathe in

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27
Q

What is the expiratory reserve volume?

A

The extra volume of air that can be expelled by an active expiratory effort AFTER passive expiration

28
Q

What is the the residual volume?

A

The volume of air remaining in the lungs after the most forceful expiration

29
Q

What is the functional residual capacity?

A

The amount of air that remains in the lungs at the end of normal expiration

30
Q

What is the vital capacity?

A

Tidal volume + inspiratory reserve volume + expiratory reserve volume

The maximum amount of air an individual can expel from the lungs after filling the lungs to the maximum extent and then expiring to a maximum extent

31
Q

What is the total lung capacity?

A

Vital capacity + residual volume

The maximum amount of air the lungs can be expanded with the greatest amount of effort

32
Q

What factors affect diffusion in the lung?

A
  1. Thickness of membranes
  2. Surface area
  3. Diffusion coefficient of gas
  4. Partial pressure difference
33
Q

What is Fick’s law

A

Ficks law states that the rate of diffusion of a gas through a tissue sheet is proportional to the area and pressure difference across it, and inversely proportional to the thickness

34
Q

What happens to the blood vessel if the concentration of O2 in an alveoli decreases?

A

Blood vessels constrict → increase vascular resistance
Distributes blood flow to where the lungs are better aerated

35
Q

What occurs to V/Q in the following scenarios?

  1. Without ventilation
  2. Without perfusion
A
  1. V/Q = 0
  2. V/Q = infinity
36
Q

What diseases can lead to a low V/Q (poor ventilation, decreased PaO2)

A
  1. Chronic bronchitis
  2. Asthma
  3. Pulmonary edema

Ventral lungs have slightly lower V/Q

37
Q

What diseases can lead to a high V/Q (poor perfusion, increased PaCO2)

A
  1. Pulmonary thromboembolism
    * Dorsal lungs have a slightly higher V/Q
38
Q

What can cause pulmonary edema (general mechanisms)?

A
  1. Increased hydrostatic pressure
  2. Decreased oncotic pressure
  3. Failure of lymphatic drainage
  4. Increased vascular permeability
39
Q

What is perfusion limited gas exchange?

A

Illustrated by O2 and NO

  • The gas equilibrates early along the length of the pulmonary capillary
  • The partial pressure of the gas in arterial blood becomes equal to the partial pressure in the alveolar air
  • Diffusion of the gas can only be increased with increased blood flow
40
Q

What is diffusion limited gas exchange?

A

Illustrated by CO

  • The gas does not equilibrate by the time the blood reaches the end of the pulmonary capillary
  • The partial pressure of the gas between alveolar air and pulmonary capillary blood is maintained
  • Diffusion continues as long as the partial pressure gradient is maintained
41
Q

What are the 5 causes of hypoxemia?
Which will not respond to oxygen therapy?

A
  1. Hypoventilation (Decreased PAO2)
  2. Diffusion impairment
  3. V/Q Mismatch
  4. Shunts
  5. Low FiO2

*Shunt will not respond to 100% O2

42
Q

What are the causes for tissue hypoxia?

A
  • Hypoxic hypoxia (low blood oxygen overall)
  • Anemia hypoxia (recall the oxygen content equation)
  • Circulatory hypoxia (decreased tissue perfusion)
  • Histotoxic hypoxia (Cyanide)
43
Q

In what zone of the lung is blood flow the lowest?

44
Q

Where is the V/Q ratio the highest?

45
Q

How are PO2 and PCO2 affected in airway obstruction?

A

V/Q = 0
Will approach their values in mixed venous blood

46
Q

How are PO2 and PCO2 affected in pulmonary embolism?

A

V/Q = infinity
Will approach their values in inspired air

47
Q

What is normal tidal volume?

A

10-15 ml/kg

48
Q

The A-a gradient should always be (number)

49
Q

What does an increased A-a gradient indicate?

A
  1. Shunt
  2. V/Q Mismatch
  3. Diffusion impairment
50
Q

A low PaO2, high PCO2, and normal A-a gradient would indicate what?

A

Hypoventilation with normal lungs

51
Q

The (PO2/PCO2) is the most important regulator of ventilation and most of the control is via the (peripheral/central) chemoreceptors

A
  1. PCO2
  2. Central
52
Q

Peripheral chemoreceptors respond to changes in which gases

A
  • Respond non-linearly to changes in PaO2, with maximum response when PaO2 < 50 mmHg
  • Also respond to increased PCO2 and H+, more rapidly than central
53
Q

Which chemoreceptors can respond to hypoxia?

A

Peripheral

54
Q

Which conditions will not respond to 100% oxygen supplementation?

A
  1. Cyanide toxicity
  2. Shunt
  3. V/Q to infinity (ventilation but no perfusion)
55
Q

How does the lung adapt to accommodate more blood during exercise?

A

Increases pulmonary blood flow (blood vessel dissension)
Decreases physiologic dead space (blood vessel recruitment)

56
Q

What does a right shift of the oxygen dissociation curve mean?

A

Right shift = decreased oxygen affinity of haemoglobin allowing more O2 release to tissues

57
Q

What are the 4 types of lung receptors

A

Pulmonary stretch receptors (slow acting)
Irritant receptors (fast acting stretch receptor - bronchoconstriction and hyperpnea)
J receptors
Bronchial C Fiber

REATHING)

58
Q

What is the A-a gradient and how do you calculate it

A

The A-a gradient is the difference between the theoretical value of oxygen partial pressure in the alveolus (PAO2) and the actual partial pressure of oxygen in the blood (PaO2).

PAO2 = FiO2 x (Atmospheric Pressure (760mmHg) – Saturated Water Vapour Pressure (47mmHg)) – 1.2(PCaO2).

So - PAO2 = 150 – 1.2(PaCO2)

A-a gradient = PAO2-PaO2 or
A-s = 150 – 1.2(PaCO2) - PaO2

59
Q

What is the P/F ratio and how do you calculate it?

A

PaO2/FiO2

Normal PaO2/FiO2 on room air should be approx. 470

Mild ARDS < 300
Moderate ARDS <200
Severe ARDS <100

60
Q

How is total ventilation or minute ventilation calculated?

A

minute ventilation = tidal volume x respiration frequency

Tidal volume in a normal dog = 10-20ml/kg

61
Q

How is alveolar ventilation calculated?

A

Alveolar ventilation is the volume of fresh gas (non-dead space) entering the respiratory zone per minute

(Vtidal - Vdead space) x no of breaths per minute

62
Q

What is the difference between anatomic and physiological dead space?

A

Anatomic dead space is the volume of the conducting airways - approx. 150ml in the adult
Physiologic dead space is the volume of gas that does not eliminate CO2

Physiologic dead space is affected by lung disease

63
Q

What are the other function of the lung apart from gas exchange?

A
  • removal of vasoactive substanceds (Serotonin, bradykinin, Norepinephrine, AT1)
  • Biological activation (ACE)
  • Coagulation
  • Synthesis (surfactant, mucous IgA)
64
Q

What are the main differences of pulmonary circulation compared to systemic?

A
  • Low pressure - Mean PA pressure is 15mmHg
  • Thin vessel walls - arteries lack smooth muscle in walls
  • Pressure from alveoli can collapse surrounding capillaries
65
Q

How do you calculate vascular resistance

What is the calculation for pulmonary vascular resistance

A

(input pressure - output pressure) / blood flow

mean PA pressure - LA pressure/cardiac output

66
Q

An initial increase in mean PA pressure or venous pressure will cause what to happen to PVR?

A

Decrease in PVR due to recruitment and distension of capillaries

67
Q

Which local vasoactive substances can cause vasodilation

A

Nitric oxide, Sildenafil, Endothelin 1

Generals G.O.A.T (8 decks)

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