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Board Review CRNA (Sweat Book) > Control of ventilation & Pulmonary mechanics > Flashcards

Control of ventilation & Pulmonary mechanics Flashcards

1
Q

The central chemoreceptors are stimulated by _______ H+; an increase in cerebral spinal fluid CO2 automatically leads to an ______ in H+.

A

increased; increase

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2
Q

______ drives normal respiration.

A

CO2

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3
Q

The peripheral chemoreceptors are stimulated by ______ PCO2, ______ pH, and/or _____ PaO2 (<60mmHg).

A

increased; decreased; decreased

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4
Q

The _______ nerve carries sensory impulses from the carotid bodies, and the _____ nerve carries sensory impulses from the aortic bodies and also from stretch receptors in the lung parenchyma.

A

glossopharyngeal nerve–> carotid bodies

vagus nerve—> aortic bodies and lung parenchyma

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5
Q

The glossopharyngeal nerve carries sensory impulses from the _______, and the vagus nerve carries sensory impulses from the _______ and also from stretch receptors in the _______.

A

The glossopharyngeal nerve carries sensory impulses from the carotid bodies, and the vagus nerve carries sensory impulses from the aortic bodies and also from stretch receptors in the lung parenchyma.

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6
Q

The diaphragm is the muscle of inspiration. ______ % of TV alone is all due to the diaphragm. The rest is from the _________ nerve.

A

50-75%; external intercostal

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7
Q

_______ are our built in ABG’s.

A

chemoreceptors

-only kick in when PaO2 <60

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8
Q

Why is it BAD to give chronic O2 patients too much O2?

A

because they rely on their chemoreceptors–> their chemoreceptors kick in when PaO2 <60… we knock out this function when giving them O2

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9
Q

DRG stands for:

A

doral respiratory group

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10
Q

VRG stands for:

A

ventral respiratory group

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11
Q

DRG generates the basic rhythm of respiration, it is found in the medulla, and may be considered the ________.

A

inspiratory pacemaker

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12
Q

The VRG can influence BOTH _______ and ________.

A

inspiration and expiration (internal intercostals)

*probably comes into play when high levels of ventilation are required

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13
Q

The pneumotaxic center is located _________. The apneustic center is located ________.

A

pneumo: high in the pons
apneu: low in the pons

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14
Q

The ________ SHUTS OFF inspiration.

A

pneumotaxic

*apneustic center also has similar function

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15
Q

The ______ work together to control the RATE and DEPTH of inspiration.

A

pneumotaxic and apneustic centers

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16
Q

The smooth muscle of the bronchi and bronchioles has receptors that FIRE when STRETCHED, which reflexly tends to INHIBIT inspiration. This is called the _______.

A

Hering-Breuer reflex

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17
Q

In adults, the Hering-Breuer reflex does not become important until TV exceeds ____.

A

1.5L

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18
Q

In neonates the Hering-Breuer reflex is _______ and ______.

A

STRONG and RELEVANT

*protective mechanism for preventing excess lung inflation

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19
Q

In the Hering-Breuer reflex, the ______ nerve carries afferent (sensory) information.

A

vagus

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20
Q

Central chemoreceptors respond to _________.

A

hydrogen ions
*H+ concentration in CSF increases as PaCO2 increases and decreases as PaCO2 decreases–> normally CO2 drives ventilation

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21
Q

Peripheral chemoreceptors respond to 3 things???:

A

1) decreased PaO2 <60
2) increased H+ concentration
3) increased PaCO2

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22
Q

When the partial pressure of CO2 in CSF increases, the H+ and HCO3- ion concentrations increase immediately…. who’s principle or law applies?

A

Le Chatliers—> derives from law of mass action—> want to achieve equilibrium

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23
Q

Ventilation and perfusion in the UPRIGHT, SPONT VENT, NON-INTUBATED person is BEST in the ______ lung.

A

DEPENDENT

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24
Q

The intrapleural space (potential space) is found between parietal pleura of internal chest wall and visceral pleura covering the lung. The intrapleural pressure is “negative” (subatmospheric) b/c the lungs recoil inward and the chest wall recoils outward–> when the inward and outward forces are equal this is called FRC. Which part is altered in the obese patient? In the patient with emphysema?

A

obese= chest wall
emphysema= lung
in both instances FRC is altered
~ 3L FRC is normal in the upright, spont breathing 70kg person

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25
Q

During inspiration intrapleural pressure becomes more _______. Air enters the lung because the intrapulmonary pressure is ______.

A

negative (subatmospheric–> can’t actually have a negative pressure)

subatmospheric

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26
Q

The _______ couple the lungs to the chest wall.

A

pleural membranes

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27
Q

_______ pressure (pressure between the inside of the chest wall and lungs) is ALWAYS negative (subatmospheric) during normal tidal breathing.

A

intrapleural pressure

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28
Q

Intrapleural pressure becomes more ______ during inspiration and less _______ during expiration. Intrapulmonary pressure is ______ during inspiration and more ______ during expiration.

A

Intrapleural becomes more negative during inspiration and less negative during expiration…. intrapulmonary is negative during inspiration and positive during expiration

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29
Q

What are 2 scenarios when intrapleural pressure may become positive?

A

1) during forced expiration

2) expiratory effort against a closed glottis (valsalva)

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30
Q

Describe the alveoli size in inspiration and expiration in the UPRIGHT, SPONT VENT, NON-INTUBATED patient.

A

non-dependent alveoli started big and got bigger (so not much change overall); dependent alveoli started small and for bigger (so larger change= BEST ventilation)
*think of a hanging slinky in regards to alveoli

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31
Q

1 atm= ____ mmHg= ______ cm H2O

A

760; 1,033

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32
Q

The dependent lung is dependent on the diaphragm… if you lose diaphragmatic tone you lose _____.

A

dependency

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33
Q

Calculate normal ventilation perfusion mismatch.

A 
V= 4 L/Min (norm MV)
-----------------                  =   0.8
Q= 5 L/min (norm CO)
  1. 8 is good but not quite keeping up with perfusion… if it is >1.0 then the perfusion is not keeping up with ventilation
    ex) V/Q=3.5…… ventilation is delivering O2 3.5 times quicker than blood flow can take it away
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34
Q

In the awake and spont ventilating pt that is standing, how does PAO2 and PACO2 compare in the apex and base of the lungs?

A

increased PAO2 in apex, less PACO2 d\t less exchange… INVERSE at base

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35
Q

In the awake and spont ventilating pt that is lying supine (prone or lateral decubitus), how does PAO2 and PACO2 compare in the apex and base of the lungs?

A

it would be the same in apex as it is the base

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36
Q

Describe how positive pressure ventilation affects the ventilation and perfusion of the lung in a patient lying lateral decubitus that is ANESTHETIZED AND PARALYZED.

A

the dependent lung is compressed by the weight of the abdominal contents (paralyzed); with positive pressure ventilation, inspiratory gases are preferentially distributed to the nondependent lung–> clinically significant V/Q mismatch–> nondep lung is well ventilated but poorly perfused (deadspacing)….. the dependent lung is well perfused, but poorly ventilated (shunting)

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37
Q

Absolute shunt = ________

A

V/Q = 0

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38
Q

Venous admixture, or partial shunt= _______

A

0< V/Q < 0.8

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39
Q

Partial alveolar deadspace, or partial deadspacing= _____

A

0.8< V/Q < infinity

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40
Q

V= 0 L/min
——————- = 0
Q= 5 L/min
the above is an example of what?

A

absolute shunt

ex) tumor obstructing the bronchus

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41
Q

V= 4 L/min
——————- = infinity
Q= 0 L/min
the above is an example of what?

A

absolute deadspacing

ex) pulmonary emboli

42
Q

PaO2 ALWAYS ______ when there is a V/Q mismatch.

A

decreases

43
Q

Name 3 causes of low PaO2.

A

1) low inspired O2
2) hypoventilation
3) V:Q mismatching

44
Q

How can you determine the difference between hypoventilation or V/Q mismatch as a source of low PaO2 in a patient?

A

you must calculate the alveolar arterial blood gradient for O2 and/or CO2
*if the gradient is HIGH then it is the result of mismatch, if it is NORMAL then the pt is hypoxic

45
Q

There would be _____ A-a gradients if the lungs had PERFECT matching of ventilation and perfusion.

A

No

*but normal lungs exhibit some V/Q mismatching (0.8–> more perfusion than ventilation)

46
Q

The normal PAO2-PaO2 gradient is ______ when breathing room air.

A

5-15 mmHg (this increases when inspired O2 increases)

*while breathing 100% O2 the normal Aa gradient is <100

47
Q

The normal PACO2-PaCO2 gradient is ______ when breathing room air.

A

2-10 mmHg

*regardless of inspired O2

48
Q

What is a way of obtaining the average PACO2?

A

PACO2 = ETCO2

49
Q

How do you calculate the PAO2-PaO2 gradient?

A

just subtract one from the other

50
Q

How can you estimate the PaO2 in a healthy patient?

A

multiply the % O2 by 5

60% x 5= 300 mmHg = PaO2

51
Q

How can you estimate the PAO2 in a healthy patient?

A

multiply the % O2 by 6

60% x 6= 360 mmHg = PAO2

52
Q

What is the normal PaO2/PAO2 ratio, and what does a decrease in this ratio reflect?

A

normal= >0.75

a decrease reflects a possible shunt

53
Q

What is a right to left shunt?

A

intracardiac shunt–> blood pumped by right heart passes to left heart without being oxygenated
*from anatomic defect or that blood passes through lungs without coming in contact with oxygen in alveoli–> as in ARDS

54
Q

What is a left to right shunt?

A

intracardiac shunt–> blood is pumped from left heart back to right as in a neonate when blood is shunted through the ductus arteriosus or formamen ovale

55
Q

In ANY position, the dependent regions of the lungs are better perfused and better ventilated in the ______.

A

awake, spontaneously breathing subject

56
Q

Ventilation perfusion ratios are normally ____ in dependent lung areas and ______ in nondependent lung areas.

A

smaller; larger

57
Q

What are the two results of normal slight V/Q mismatching?

A

1) O2 A-a gradient of 5-15mmHg….. arterial blood is 5-15mmHg less than the partial pressure of oxygen in mixed alveolar gas
2) CO2 A-a gradient 2-10mmHg….. CO2 in arterial blood slightly exceeds the partial pressure of CO2 in mixed alveolar gas

58
Q

What are the 4 zones of West?

A

just move the “A” to the right for the first 3
I) A>a>v
II) a>A>v
III) a>v>A
IV) a>isf>v>A
IV)= not normal–> wet lungs–> edema–> additional pressure was added
*remember wherever Alveolar pressure is in the “pecking” order is the name of the zone

59
Q

Explain zone 1.

A

since arterial pressure is basically negligible–> alveolar pressure exceeds pulmonary artery pressure–> the distensible capillaries of the alveolar wall are collapsed–> No blood flow in Zone I

60
Q

Explain zone II.

A

pulmonary artery pressure exceeds alveolar pressure–> there is blood flow in zone 2, and blood flow is proportional to pulm artery pressure minus alveolar pressure (Pa-PA gradient)—> after blood passes through the alveoli of zone 2 it falls into the pulmonary venous system like a waterfall–> zone 2 is waterfall zone

61
Q

Explain zone III.

A

blood flow is proportional to the pulmonary artery pressure minus pulmonary vein pressure gradient. The tip of a Swanz Ganz catheter should be placed in zone 3

62
Q

Explain zone IV.

A

BF is proportional to the pulmonary artery pressure minus pulmonary interstitial fluid pressure gradient. zone 4, like zone 1 is a pathological zone that normally is not present. zone 4 is present with pulmonary edema

63
Q

West’s zones describe ______ in the lungs.

A

PERFUSION

64
Q

Zone _____ is better ventilated, better perfused, has a lower V/Q mismatch/ratio, has a less negative intrapleural pressure, and smaller alveoli.

A

3

65
Q

Preoxygenation with 100% O2, and spontaneous ventilation with a tight fitting mask for ____ minutes can furnish up to _____ min of O2 reserve following apnea.

A

5 min provides 10 min reserve

66
Q

Why do we preoxygenate=denitrogenate?

A

to fill the FRC with O2–> provides a reservoir to maintain PaO2 during apnea

67
Q

What is the normal oxygen consumption? (VO2)

A

250ml/min

68
Q

Given the patient has normal O2 consumption (VO2), how long will it take for a patient to develop deleterious side effects following apnea if 2500mL of O2 is found in FRC after preoxygenation?

A

2500/250= 10 min

69
Q

What is hypoxic pulmonary vasoconstriction?

A

-in response to alveolar hypoxia, the alveolar arterioles constrict, thereby decreasing shunt blood flow

70
Q

Name some pharmacologic things that can decrease hypoxic pulmonary vasoconstriction.

A

1) direct-acting vasodilators–> nitroprusside, nitroglycerin, hydralazine–> increasing shunt and decreasing PaO2
2) volatile anesthetics–> at higher concentrations (> 1 MAC)

71
Q

What 3 measures cannot be measured directly with spirometry?

A

1) FRC
2) RV
3) TLC

72
Q

Name 3 methods for measuring FRC.

A

1) helium dilution
2) nitrogen washout
3) body plethysmography (based on Boyle’s Law)

73
Q

What is FEV1?

A

forced exp volume in one second

74
Q

What is FVC?

A

forced vital capacity–> volume of gas that can be exhaled during a forced expiratory maneuver

75
Q

What is a ratio that is useful to distinguish between restrictive and obstructive diseases?

A

FEV1/FVC ratio

76
Q

What is FEF 25-75?

A

rate of flow occurring in a forced expiratory flow from the point where 25% of the FVC has been exhaled to the point where 75% has been exhaled—> BEST test for assessing small airway disease

77
Q

Name common obstructive airway diseases.

A

Airways are obstructed–> asthma, COPD (bronchitis, emphysema)

78
Q

Name common restrictive airway diseases.

A

expansion of lungs and/or chest wall is restricted–> pulmonary fibrosis, pneumothorax, chest wall disease (scoliosis), neuromuscular disease (amyotrophic lateral sclerosis, myasthenia gravis)

79
Q

What is a normal FEV1?

A

4.0 L/min

80
Q

What is a normal FVC?

A

5.0 L/min

81
Q

What is a normal FEV1/FVC ratio?

A

normal is usually >0.7

82
Q

Using the FEV1/FVC ratio how can you tell whether or not it is restrictive disease or obstructive disease?

A

obstructive if FEV1 and FVC are LOW
AND
FEV1/FVC ratio 0.7

83
Q

Restrictive, Obstructive, or Normal?
FEV1= 3.6
FVC= 4.8

A

both are relatively normal
ratio= 0.75
NORMAL

84
Q

Restrictive, Obstructive, or Normal?
FEV1= 1.8
FVC= 2.2

A

both are LOW
ratio= 0.8
this is restrictive

85
Q

Restrictive, Obstructive, or Normal?
FEV1= 2.2
FVC= 4.8

A

ratio= 0.45

possible obstructive disease

86
Q

A normal flow volume loop looks like _______. restrictive? obstructive?

A

an upside down ice cream cone or a pointed side up guitar pic

restrictive: baby ice cream cone…. restricted= smaller volumes
obstructive: one side of the ice cream cone appears caved in and lung volumes are greater

87
Q

______ is shown on a flow volume loop to be impaired when there is a variable extrathoracic obstruction.

A

inspiration

88
Q

_______ is shown on a flow volume loop to be impaired when there is a variable intrathoracic obstruction.

A

expiration

89
Q

________ is shown on a flow volume loop to be impaired when there is a large, fixed airway obstruction.

A

inspiration and expiration

90
Q

As you move along a tube the pressure will ______.

A

decrease—> physiologic basis of airway closure

91
Q

How are CC and CV measured?

A

by nitrogen washout and helium dilution methods

92
Q

How does closing volume in the older healthy adult differ than that of a young healthy adult?

A

airway closure tends to close in the TV instead of after TV… causing air trapping

93
Q

In a young, healthy adult…. if vital capacity is 4,500mL when would airway closure begin?

A

typically 10% of VC in young and healthy… so,

4500 x 0.10= 450mL so airway closure begins when 450mL of the VC has been exhaled

94
Q

The volume at which airway closure begins ______ progressively with age.

A

increase

95
Q

Closing volume is _______ in obstructive pulmonary disease.

A

increased

  • emphysema–> loss of collagen and elastin
  • chronic bronchitis–> airways are narrower–> pressure drop along the airways is greater
  • asthma–> airways narrowed
96
Q

What are other conditions that can increase closing volume?

A

smoking, bronchospasm, airway secretions, fluid retention, anesthesia/surgery

97
Q

Does pulmonary compliance increase or decrease with age? Why?

A

it increases with age–> elastin and collagen breakdown with age, so the lung tissue becomes easier to distend (elasticity decreases)

98
Q

How does FRC change with age?

A

since the lung does not recoil inward with as much force, FRC increases slightly with age (~10%)

99
Q

Does chest wall compliance increase or decrease with age?

A

decreases

100
Q

Peripheral chemoreceptors are most sensitive to _____.

A

decreased Pa O2 (<60)

101
Q

What is the problem if the patient has a segment of lung with a ventilation:perfusion ratio of zero?

A

The patient has a left to right shunt (not sure, I thought it was right to left)

102
Q

What enzyme is responsible for producing bicarbonate in the red blood cell?

A

carbonic anhydrase

Board Review CRNA (Sweat Book) (38 decks)

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