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First Aid 2014 > RESPIRATORY: 599 - 600 > Flashcards

RESPIRATORY: 599 - 600 Flashcards

1
Q

Characterize the normal pulmonary circulation system in terms of resistance, pressure, and compliance.

A

Low resistance
Low pressure
High compliance

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2
Q

What is hypoxic vasoconstriction?

A

A decrease in PAO2 shifts blood away from poorly ventilated regions of lung to well-ventilated regions of lung

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3
Q

What is the major complication of pulmonary hypertension?

A

Cor pulmonale and subsequent right sided heart failure (JVD, edema, hepatomegaly)

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4
Q

Describe perfusion limited gas exchange.

A

Gas equilibrates early along the length of the capillary (i.e. maximal gas exchange).

Diffusion can only be increased if blood flow itself is increased.

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5
Q

Describe diffusion limited gas exchange.

A

Gas does not equilibrate by the time blood reaches the end of the capillary (i.e. less than maximal gas exchange).

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6
Q

What gases are perfusion limited?

A

O2 (normal health), CO2, N2O

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7
Q

What gases are diffusion limited?

A

O2 (in cases of emphysema, fibrosis), CO

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8
Q

What is the equation for the volume of a gas that will diffuse across a membrane?

A

Vgas = A/T x Dk(P1 - P2)

where V = volume, A = area, T = thickness, Dk = diffusion constant, P1 - P2 = difference in partial pressures

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9
Q

What happens to the diffusion membrane in emphysema?

A

Decrease in area

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10
Q

What happens to the diffusion membrane in pulmonary fibrosis?

A

Increase in thickness

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11
Q

How do we relate pulmonary vascular resistance to pressure and flow?

A

General equation: delta P = Q x R so R = delta P / Q
where delta P = pressure difference, Q = flow, R = resistance

So in this case: PVR = (P pulmonary artery - P left atrium) / cardiac output

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12
Q

What is the equation for calculating resistance based on all of its components?

A

R = 8nl / (πr^4)

where n = viscosity of blood, l = vessel length, r = vessel radius

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13
Q

What is the alveolar gas equation?

A

PAO2 = PIO2 - PaCO2/R
where PAO2 = alveolar PO2, PIOS = PO2 in inspired air, PaCO2 = arterial PCO2, R = respiratory quotient = CO2 produced/O2 consumed

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14
Q

What is a normal value for PIO2?

A

150

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15
Q

What is a normal value for the respiratory quotient?

A

0.8

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16
Q

What is the A-a gradient?

A

PAO2 - PaO2

17
Q

What is a normal value for A-a gradient?

A

10-15 mm Hg

18
Q

When do we see an increased A-a gradient?

A

In cases of hypoxemia

19
Q

What can cause an increased A-a gradient?

A

Shunting, V/Q mismatch, fibrosis (from limited diffusion)

20
Q

What are the three types of oxygen deprivation?

A
  1. Hypoxemia - decrease in PaO2 (in oxygen getting to the blood)
  2. Hypoxia - decreased O2 delivery to tissue
  3. Ischemia - loss of blood flow
21
Q

How can we break up the causes of hypoxemia?

A

Normal A-a gradient vs. Increased A-a gradient

22
Q

When do we see hypoxemia with a normal A-a gradient?

A

High altitude or hypoventilation

23
Q

What are 4 causes of hypoxia?

A
  1. Decreased cardiac output
  2. Hypoxemia
  3. Anemia
  4. CO poisoning
24
Q

What are 2 causes of ischemia?

A
  1. Impeded arterial flow

2. Decreased venous drainage

25
Q

What is the ideal V/Q ratio?

A

1

26
Q

What do V and Q stand for in V/Q ratio?

A 
V = ventilation
Q = perfusion
27
Q

Where are ventilation and perfusion greatest in the lung?

A

Both are greater at the base of the lung compared to the apex

28
Q

Describe how the V/Q ratio changes between apex vs. base of the lung.

A

Higher in the apex (wasted ventilation) than the base (wasted perfusion)

In the apex- around 3, in the base - around 0.6

29
Q

Why does the V/Q ratio approach 1 during exercise?

A

Increase in cardiac output results in vasodilation of apical capillaries

30
Q

Why does TB like the apex of the lung?

A

TB is an organism that thrives in high O2 so it prefers the apex where the V/Q ratio is high meaning more wasted ventilation

31
Q

Compare PA, Pa, Pv in zones 1, 2, 3.

A

Zone 1: PA > Pa > Pv
Zone 2: Pa > PA > Pv
Zone 3: Pa > Pv > PA

32
Q

What is it called when V/Q approaches 0?

A

Shunt (airway obstruction)

33
Q

What is it called when V/Q approaches infinity?

A

Dead space (blood flow obstruction)

34
Q

In which scenario (shunt vs. dead space) will 100% O2 improve the PO2?

A

Dead space - assuming that the obstruction is < 100%

First Aid 2014 (24 decks)

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