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CPR Test 2 > 57: Ventilation Perfusion > Flashcards

57: Ventilation Perfusion Flashcards

1
Q

Alveolar Ventilation (VA)

A

4L/min at rest

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2
Q

Perfusion (Q)

A

cardiac output 5L/min

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3
Q

Alveolar- arterial oxygen (A-a O2) gradient

A

5 to 15 mm

Hg is due to venous admixture

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4
Q

Hypoxemia

A

PaO2 below 85 mm Hg

Increased venous admixture results in low O2 tension in
the blood

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5
Q

Dead Space

A

V(D)

Volume of inhaled air that does not
participate in gas exchange

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6
Q

Anatomic dead

space

A

Conducting airways

150 mL

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7
Q

Alveolar dead

space

A

Alveoli with no perfusion

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8
Q

Physiologic Shunt

A

total venous

admixture

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9
Q

Cause 1 of Physiologic Shunt?

A

Anatomic shunt

right –to –left shunt

ex: bronchial circulation

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10
Q

Cause 2 of Physiologic Shunt?

A

50% from low VA/Q

ex: partially obstructed airway

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11
Q

“wasted air”

A

all inspired air
does not participate
in gas exchange

anatomic + alveolar = physiologic dead
space

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12
Q

“wasted blood”

A

all blood entering the lung is not fully oxygenated

anatomic + low (VA/Q) ratio = physiologic shunt

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13
Q

Lung is slinky

A

top: coils are pulled apart, weight pulling down on it
middle: coils tighter than the top, half of weight pulling down on it
bottom: coils are tighter, little weight pulling down on it
* lungs rest on abdomen

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14
Q

Pressure Volume at FRC

A

apex less compliant than base

at rest: apex 70% and base 15% distended

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15
Q

What is the change in volume at apex during inspiration?

A

Significantly less than base

ventilation gradient aligned with gravity

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16
Q

Pulmonary circulation

A

high-flow,

low-pressure, low-resistance system

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17
Q

Is the base or apex of the lung more compliant?

A

The base of the lung

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18
Q

There is more resistance to blood flow toward the apex of the lung b/c upward flow runs against…….

A

Hydrostatic pressure

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19
Q

High alveolar volume in the apex reduces ,,,,,,,,

A

Blood flow (this restriction is not present when alveolar pressure falls below pulmonary arterial pressure)

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20
Q

Apex of Lung: Ventilation

  • Intrapleural pressure more………..
  • Greater transmural pressure gradient
  • Alveoli ………….
  • Less ventilation
A

Negative

Larger, Less compliant

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21
Q

Apex of Lung; Perfusion

  • Low Intravascular pressures
  • …….. Recruitment and Distention
  • …….. Resistance
  • Less blood Flow
A

Less Recruitment

Higher Resistance

22
Q

Base of Lung: Ventilation

  • Intrapleural pressure less negative
  • ……….. Transmural Pressure Gradient
  • Alveoli…………
  • More Ventilation
A

Smaller Transmural Pressure Gradient

Alveoli smaller, more compliant

23
Q

Base of Lung: Perfusion:

  • ………. Vascular Pressures
  • ……….. Recruitment and Distention
  • Lower resistance
  • Greater Blood Flow
A

Greater vascular pressures

More Recruitment

24
Q

………….. and ……… are both gravity dependent

A

Ventilation and Blood Flow

25
Q

Ventilation-perfusion ratio ……..down the lung

A

Decreases

26
Q

……….. is more efficient at the apex of the lung as compared to the base.

A

Gas Exchange

27
Q

For low V/Q ratio (lots of blood or too little ventilation); causes the blood coming into the area to be directed to other parts of the lung.

A

Hypoxic vasoconstriction

28
Q

for high V/Q ratio, the bronchi will constrict slightly to increase the resistance and decrease the amount of ventilation coming into an area that is not well perfused thus limiting the amount of alveolar dead space

A

Bronchoconstriction

29
Q

The patient with a V/Q = 0 may most likely not benefit from supplemental oxygen because there is ………

A

No ventilation

30
Q

Regional low VA/Q ratio causes A-a O2 gradient to …..

A

Increase

31
Q

An Anatomic shunt causes A-a O2 gradient to …..

A

Increase

32
Q

Diffusion block causes A-a O2 gradient to …..

A

Increase

33
Q

How does hypoventilation effect A-a O2 gradient?

A

No Change

34
Q

If the patient has hypoxemia and PaCO2 is less than 40 and A-a is outside of the 5-20 mmHg points to …….

A

Hypoventilation

35
Q

…….. has high alveolar pressure –which increases resistance in pulmonary circulation

A

Apex of lung

36
Q

V/Q = 0 means

A

Perfusion of an area with no ventilation i.e. a shunt

37
Q

V/Q = infinity means

A

Dead space –ventilation with no perfusion

38
Q

The healthy lung has ……. the majority of respiratory segments blood flow (by controlling pulmonary capillary flow) to ventilation –and therefore have a V/Q of ~1

A

Matched

39
Q

V/Q mismatch always ……the oxygen content of the venous admixture and increases the A-a gradient.

A

Lowers

not necessarily hypercapnia though

40
Q

↑V/Q = >1 =

A

↑PO2 ↓PCO2

41
Q

V/Q = 1 =

A

PO2 100, PCO2 40

42
Q

↓V/Q = <1 =

A

↓PO2 ↑PCO2

43
Q

With high altitude, alveolar PO2 ……… which results in decreased arterial PO2 (hypoxemia)

A

Decreases

44
Q

………. is stimulated by the hypoxemia experienced by carotid/aortic bodies

A

Ventilation

45
Q

Minute alveolar ventilation ……….in an attempt to restore blood oxygen levels

A

Increases

46
Q

During a rapid Altitude Increase, leads to:

A
  • Hypoxemia –stimulated ventilation
  • PCO2 declines producing resp. alkalosis
  • These tend to counter the increase in ventilation due to hypoxia
  • Over 2-3 days –blood pH is corrected (acidified) by renal excretion of HCO3-. CSF also returns to normal with HCO3excretion.
  • Full hypoxic ventilatory drive is then restored
47
Q

How can polycythemia be caused by hypoxemia?

A

Low PO2 of kidney stimulates the release of erythropoietin –which in turn stimulates bone marrow to increase RBC production

48
Q

During mountain sickness, the pulmonary hypoxic vasoconstriction ……. pulmonary vascular resistance
–……… hydrostatic pressure in the pulmonary circulation

A

Increases

Increasing

49
Q

During mountain sickness, ………sympathetic stimulation and cardiac output due to arterial chemoreceptor stimulation

A

Increase

50
Q

…….. is sensitive to hypocapnea –it is a strong cerebral vasoconstrictor

A

Cerebral Circulation

51
Q

Common symptom of altitude sickness

A

Headaches, mental confusion

52
Q

Low PO2 leads to cerebral vessel ……….. and hyperperfusionof the vessels. Increases the likelihood of cerebral edema

A

Vasodilation

CPR Test 2 (28 decks)

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