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Apex > Respiratory Physiology I > Flashcards

Respiratory Physiology I Flashcards

1
Q

List the muscles of expiration

A
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2
Q

List the muscles of inspiration

A
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3
Q

Contraction of the inspiratory muscles reduces _____ and increases ______. What law is this an example of?

A

thoracic pressure

thoracic volume

Boyle’s Law

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4
Q

During inspiration, which muscle(s) increase A-P diameter?

Which muscle(s) increase superior-inferior dimension?

A

External intercostals

Diaphragm

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5
Q

What are the accessory muscles of inspiration?

A

Sternocleidomastoid

Scalenes

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6
Q

Active exhalation is carried out by:

What’s a good mnemonic for this?

A

the abdominal muscles

I let the air out of my TIREs:

Transverse Abdominus

Internal Oblique

Rectus Abdominus

External Oblique

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7
Q

What vital capacity is required in order to form a good cough?

A

15 ml/kg

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8
Q

The functional divisions of the airway can be divided into three zones:

A

Conducting

Transitional

Respiratory

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9
Q

The conducting zone begins at the ____ and ends at the ______

A

Nares

Terminal Bronchioles

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10
Q

______ is the last structure perfused by the bronchial circulation

A

Terminal bronchioles

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11
Q

The transitional zone contains:

A

the respiratory bronchioles

Dual function of air conduction and gas exchange

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12
Q

The respiratory zone consists of _____ and _____

A

Alveolar Ducts

Alveolar Sacs

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13
Q

List the levels of the airway, from the trachea down

A
  1. Trachea
  2. Bronchi
  3. Bronchioles
  4. Respiratory Bronchioles
  5. Alveolar Ducts
  6. Alveolar Sacs
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14
Q

What is the last are of the airway that contains cartilage?

A

Bronchi

Bronchioles DO NOT have cartilage

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15
Q

What is the last area of the airway containing smooth mucles?

A

The alveolar ducts

The alveolar sacs are the only structures that do not have any

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16
Q

Gas exchange occurs across ____ cells by ______

A

Type 1

Diffusion

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17
Q

Alveolar Pressure is the pressure _______

Intrapleural pressure is the pressure _______

A

inside the airway

outside the airway

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18
Q

Transpulmonary Pressure = ______ - ______

A

Alveolar Pressure - Intrapleural pressure

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19
Q

If TPP is positive, the airway _______

If TPP is negative, the airway _______

A

Opens

Closes

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20
Q

DURING TIDAL BREATHING

Transpulmonary Pressure is always ______

Intrapleural pressure is always ________

A

Positive (keeps airway open)

Negative (keeps lungs inflated)

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21
Q

Alveolar pressure becomes slightly ______ during inspiration

and slightly _____ during expiration

A

negative

positive

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22
Q

There are only two times when intrapleural pressure becomes positive:

A

Forced expiration

Pneumothorax

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23
Q

What is the transpulmonary pressure?

Is air moving in or out?

A

-1

You use the first area in the lungs to deflate

15 - (+16) = -1

Out - Forced Expiration

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24
Q

What is the TPP? Is air moving out or in?

A

-1 - (-8) = 7

Air is moving in (inspiration)

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25
Q

Minute ventilation = ______ x _______

A

Tidal Volume x RR

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26
Q

Alveolar Ventilation = ________ x _________

A

(TV - dead space) x RR

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27
Q

What is the VT?

What is a normal VT?

A

Tidal Volume is the amount of gas that is inhaled and exhaled during a breath

6-8 mlkg

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28
Q

What is the VT?

What is a normal VT?

A

Tidal Volume is the amount of gas that is inhaled and exhaled during a breath

6-8 ml/kg

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29
Q

What is Vd?

What is a normal VD?

A

Dead space

~ 2 ml/kg (150 ml)

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30
Q

Any condition that increases VD also increases:

A

The PaCO2 - EtCO2 gradient

Makes it harder to expire gases from the airway, causing CO2 retention

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31
Q

How can you predict PaO2 by age?

A
32
Q

How do you calculate static compliance?

A
33
Q

How do you calculate Dynamic Compliance?

A
34
Q

What are some factors that increase dead space?

A

Anything that increases the volume of the conducting zone

OR
Reduces pulmonary blood flow

e.g. Hypotension (reduces pulmonary blood flow)

Atropine (bronchodilates, which increases the volume of the conducting zone)

PPV (increases ventilation relative to perfusion, which is another way of saying that dead space is increased)

35
Q

What are some factors that decrease dead space?

A

Anything that reduces the volume of the conducting zone or increases pulmonary blood flow

e.g. ETT, LMA, neck flexion

36
Q

What are the four types of dead space?

A

Anatomic

Alveolar

Physiologic

Apparatus

37
Q

What are two examples of apparatus dead space?

A

Heat and Moisture Exchanger

Face Mask

38
Q

What is physiologic dead space?

A

Anatomic dead space + alveolar dead space

39
Q

What causes alveolar dead space?

A

Decreased pulmonary blood flow

40
Q

What is the Vd/Vt ratio?

A

Ratio between dead space and ventilation

41
Q

What is the Vd/Vt for a 65 kg woman with a Vt of 350 ml?

A

We assume adults have a Vd of 2 ml/kg, which would mean she has 130 ml dead space

130 ml/350ml = 0.37

42
Q

How does mechanical ventilation effect Vd/Vt?

A

It increases it to about 50% (0.5)

BECAUSE

It increases the V/Q ratio, which essentially means it increases dead space

43
Q

What is the most common cause of increased Vd/Vt under general anesthesia?

A

Decreased cardiac output

If etCO2 abruptly decreases, this should be your first suspicion before looking for other causes of increased dead space

44
Q

What disease states cause increased Vd?

A

Decreased CO

COPD

PE

45
Q

Neck flexion and extension have what effect on Vd?

A

Flexion: reduces the amount of hypopharynx open, and therefore reduces dead space

Extension: opens the hypopharynx, increasing dead space

46
Q

In a circle system, dead space begins at:

A

the Y piece

47
Q

How is physiologic dead space calculated?

A

The Bohr Equation

48
Q

Many clinicians use ______ and ______ to estimate dead space

A

The difference between the PaCO2 and the etCO2

49
Q

In the textbook patient:

V =

Q =

V/Q =

A

4 L/min

5 L/min

.8

50
Q

What is compliance?

A

Change in Volume
_______________
Change in Pressure

51
Q

When upright, blood flow predominantly to the lung bases. Why doesn’t the V/Q ratio get smaller?

A

Because alveoli in the base also have higher compliance:

for a set pressure, they take in more volume

more volume = more gas exchange

52
Q

Which alveoli have the poorest compliance?

Which have the highest?

A

Apex

Base

53
Q

Describe V/Q in the non-dependent portion of the lung

A
54
Q

Describe V/Q in the dependent area of the lung

A
55
Q

What determines how “ventilated” any particular alveoli is?

A

The alveoli with the greatest ventilation are the ones that undergo the greatest volumetric change

Better compliance = better ventilation

56
Q

Is this dead space or shunting?

A

Dead Space

57
Q

Is this dead space or shunting?

A

Shunt

58
Q

What is the most common cause of hypoxemia in the PACU?

A

Atelectasis

59
Q

Blood passing through an underventilated alveoli tends to ______ CO2

A

retain

and is unable to take in oxygen

60
Q

Blood passing through an overventilated alveoli tends to ______ CO2

A

give off too much CO2 (more than the alveoli could empty out), but it can’t take up a proportional amount of oxygen

(just because you’re giving off more CO2 does not mean you’re getting more O2 because of the dissociation curve)

61
Q

Which is usually effected by a V/Q mismatch: PAO2-PaO2 or PACO2-PaCO2

Why?

A

Usually just the O2 A-a gradient is effected

The lung compensates by overinflating alveoli. This works at eliminating CO2, but not at getting O2 in

62
Q

How does the body combat shunt?

A

hypoxic pulmonary vasoconstriction reduces pulmonary blood flow to hypoventilated alveoli

63
Q

How does the body combat dead space?

A

Bronchioles constrict to minimize airflow to poorly perfused alveoli

64
Q

The law of Laplace regarding spheres states that:

A

As the radius of a sphere increases, the wall tension increases as well

65
Q

The tendency of an alveolus to collapse is directly proportional to ______

and indirectly proportional to ______

A

more surface tension = more likely to collapse

smaller radius = more likely to collapse

66
Q

Why are alveoli pressures constant, despite varying sizes?

A

Every alveolus has the same amount of surfactant

As the radius decreases, the concentration of surfactant increases

As the radius increases, the concentration of surfactant decreases

the surface tension therefore remains the same

67
Q

Zone 1 =

Zone 2 =

Zone 3 =

Zone 4 =

A
68
Q

Zone 1 is equivalent to a V/Q =

A

Infinity

69
Q

Where does Zone 1 usually occur in the lung?

A

It doesn’t. Purely pathological.

Hypotension, PE, excessive airway pressure

70
Q

Zone 3 is equivalent to a V/Q =

A

0

Shunting!

71
Q

What West Zone should a PA cath be placed in?

Why?

A

Zone 3

The pressure in the capillary is always higher than the alveolus, and the vessel is always open

72
Q

What causes Zone 4?

A

Interstitial edema, usually from:

  1. Increased hydrostatic pressure (fluid overload)
  2. Increased negative pressure (flash pulmonary edema)
73
Q

What is the most common cause of increased dead space intraoperatively?

A

Decreased cardiac output

74
Q

What is the Bohr equation?

A

Compares the partial pressure of CO2 in the blood to the partial pressure in exhaled gas. Allows us to calculate dead space.

75
Q

Why does it matter that FRC is reduced by anesthesia?

A

FRC is the reservoir of oxygen that prevents hypoxemia during apnea

If the FRC is reduced, these patients will have very, very short tolerance of apneic episodes

76
Q

What are the anesthesia-related causes of reduced FRC?

A

Apex (46 decks)

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