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Pathophysiology Thorax > Module #2: Ventilation > Flashcards

Module #2: Ventilation Flashcards

1
Q

What is the difference between Ventilation and respiration?

A

Ventilation = mechanical process of bringing air into lungs

Respiration = gas exchange that occurs in lungs (@ alveoli) and throughout the body (target tissues/capillaries)

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2
Q

Ventilation Rate

A

breaths per min

approx. 12/min

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3
Q

Minute Ventilation

A

volume of air inspired/expired per minute

@ rest = ~6 L/min

minute ventilation = (alveolar ventilation + dead space ventilation) x Respiratory Rate (RR)

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4
Q

Alveolar Ventilation

A

volume of air that reaches alveoli per minute

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5
Q

Dead Space Ventilation

A

Volume of air that DOES NOT reach alveoli per minute

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6
Q

What areas of the bran stem are involved in respiratory control?

A

Medulla and pons

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7
Q

What is the respiratory center controlling?

A

respiratory muscle contraction and relaxation

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8
Q

What are the respiratory groups in the medulla?

A

Dorsal Respiratory Group

Ventral Respiratory Group

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9
Q

Describe the Dorsal Respiratory Group (DRG) in the Medulla:
Which respiratory action is it working on?
What is its function?
Wo is it receiving inputs from?

A

works on inspiratory actions

sets AUTOMATIC rhythm of breathing

receives input from respiratory receptors (peripheral and central chemoreceptors/lung receptors); mechanism for blood CO2 and O2 levels to influence rate of ventilation

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10
Q

Describe the Ventral Respiratory Group (VRG) in the Medulla

Which respiratory action is it working on?
What is its function?

A

works on both inspiratory and expiratory actions

active when increased ventilation is required (quiet during rest)

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11
Q

What are the respiratory regions in the pons?

A

Pneumotaxic Center

Apneustic Center

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12
Q

What is the function of the Pneumotaxic and Apneustic Centers?

A

modify depth and rate of inspiration that has been set by medullary centers (DRG and VRG)

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13
Q

What other parts of the CNS can override or influence automatic ventilation?

A

motor cortex (voluntary movement)

hypothalamus

limbic system (stress/emotion)

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14
Q

Which Respiratory center do lung receptors send impulses to?

A

DRG to influence rate of ventilation

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15
Q

Describe Irritant Receptors

Location, stimuli, Action

A

Locatedin epithelium of conducting airways (mostly larger proximal airways)

Stimulated by noxious gases, particles, etc

Action: cough reflex, initiate bronchoconstriction of airway, increase ventilation rate via DRG

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16
Q

Describe Stretch Receptors

Location, stimuli, Action

A

Located in smooth muscle of conducting airways

Stimulated by stretch (takes a lot to activate in adults) primary in newborns

Decreases ventilation rate and volume via DRG

Protective mechanism

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17
Q

Hering-Breuer Expiratory Reflex

A

strech receptor reflex in newborns

helps maintain ventilation

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18
Q

Describe Juxtapulmonary Capillary (J) Receptors

Location, stimuli, Action

A

located near alveolar septum of capillaries

stimulated by elevated pulmonary capillary pressure

results in rapid, shallow breathing (also influences cardiovascular system; decrease HR, decrease BP)

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19
Q

What do central and peripheral chemoreceptors monitor?

A

pH

PaCO2

PaO2

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20
Q

Describe Central Chemoreceptors

Location, stimuli, Action

A

located in brainstem close to respiratory centers

Stimulus: monitor pH of CSF which indirectly monitors CO2 levels of arterial blood; are activated by pH decreases (means PaCO2 is increasing)

Action: stimulate respiratory centers to increase ventilation rate and depth –> blow off CO2

Misc: plays important role in acid-base compensation

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21
Q

Describe relationship between pH of CSF and CO2 in blood

A

CO2 can DIRECTLY cross BBB; H+ CAN NOT

CO2 in brain will combine w/ H2O –> carbonic acid which then dissociates into H+ + bicarbonate

when you INCREASE H+ you DECREASE pH

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22
Q

Describe Peripheral Chemoreceptors

Location, stimuli, Action

A

located in carotid body (where CCA splits into ICA and ECA) and aortic body (arch of aorta)

Stimulated by changes in PaO2; respond to hypoxic conditions

Action: increase ventilation via DRG

Misc: plays important role in acclimatization to altitude (chronic hypoxia)

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23
Q

what is the relationship between central and peripheral receptors in healthy individuals?

A

central chemoreceptors more sensitive than peripheral; more sensitive to PaCO2 levels

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24
Q

what is the relationship between central and peripheral receptors in individuals suffering from pulmonary disease state?

A

chronic hypoventilation causes central chemoreceptors to become less sensitive

peripheral receptors take over role of regulating ventilation

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25
Q

What muscles are involved in respiration during rest?

A

diaphragm

external intercostal muscles

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26
Q

What accessory muscles are involved in respiration during exercise/disease?

A

SCM/scalenes

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27
Q

What muscles are involved in expiration during rest?

A

No major muscles are involved

diaphragm relaxes and elastic recoil of lungs dominate

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28
Q

What accessory muscles are involved in expiration during exercise/disease?

A

abdominals

internal intercostals

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29
Q

What is the purpose of surfactant?

A

lowers surface tension in alveoli –> allows alveoli to expand

30
Q

What is the consequence of increased surface tension in alveoli?

A

it makes it more difficult for alveoli to expand

31
Q

Describe the relationship of surfactant and alveoli diameter

A

small radius –> surfactant makes it easier for alveoli to expand

large radius –> surfactant makes it harder to expand

32
Q

What is the consequences of inadequate surfactant?

A

surface tension increases –> alveoli collapse

decreased lung expansion

increase work of breathing

poor gas exchange

33
Q

What is the lung disease that effects premature infants?

A

Infant Respiratory Distress Syndrome (IRDS)

they have inadequate surfactant production; hard for them to breath

34
Q

How much is the Work of Breathing in a healthy individual?

A

Very low

35
Q

How much is the work of breathing in an individual suffering from respiratory disease?

A

significantly increased

lead to chronic adaptation w/ hypertrophied accessory muscles (SCM/Scalenes)

36
Q

What is the Atmospheric pressure (barometric pressure)?

A

760 mmHg @ sea level

will decrease w/ elevation

37
Q

What is Partial Pressure?

A

pressure of individual gases w/in total air pressure

PaX = % concentration X x Total pressure of gas

38
Q

What is the partial pressure of O2 in atmospheric air? (PaO2)

A

159 mmHg

PaO2 = .209 (percentage of O2 in atmospheric air) x 760 mmHg (total atmospheric pressure)

39
Q

What is the partial pressure of CO2 in atmospheric air?

A

.23 mmHg

PaCO2 = .0003 (percentage of CO2 in atmospheric air) x 760 mmHg (total atmospheric pressure)

40
Q

How is gas exchange drive in the lungs?

A

driven by pressure gradients

41
Q

How is the air pressure different in the respiratory system as compared to atmospheric air?

A

the air pressure in the lungs is LESS than the atmospheric air

total pressure decreased when air is warmed/humidified in upper respiratory tract

42
Q

How is the PaO2 different in alveoli vs pulmonary capillaries and what does that mean?

A

PaO2 is higher in alveoli than pulmonary capillaries

means O2 will diffuse from alveoli into pulmonary capillaries

43
Q

How is PaCO2 different in alveoli vs pulmonary capillaries and what does that mean?

A

PaCO2 is lower in alveoli than pulmonary capillaries

means CO2 will diffuse from pulmonary capillaries into alveoli

44
Q

What is the total pressure in respiratory tract?

A

713 mmHg

PaH2O vapor in respiratory tract = 47 mmHg

760 mmHg - 47 mmHg = 713 mmHg

45
Q

What are the partial pressures of O2 and CO2 in trachea?

A

PaO2 = 149 mmHg

PaO2 = .209 (% of O2 in air in trachea) x 713 mmHg (total pressure of air in trachea)

PaCO2 = .21 mmHg

PaCO2 = .0003 (% CO2 in air in trachea) x 713 mmHg (total pressure of air in trachea)

46
Q

What are the partial pressures of O2 and CO2 in alveoli?

A

PaO2 = 103 mmHg

PaO2 = .145 (% O2 in air in alveoli) x 713 mmHg (total pressure of air in alveoli)

PaCO2 = 39 mmHg

PaCO2 = .055 (% CO2 in air in alveoli) x 713 mmHg (total pressure of air in alveoli)

47
Q

Tidal Volume (TV)

A

Volume of air inspired or expired w/ each normal breath

500 mL

48
Q

Inspiratory Reserve Volume (IRV)

A

Volume of air that can be inspired over and above tidal volume

3000 - 3300 mL

49
Q

Expiratory Reserve Volume (ERV)

A

volume of air that be expired after expiration @ total volume

1000 - 1200 mL

50
Q

Reserve Volume (aka Residual Lung Volume) (RV)

A

Volume of air that remains in lungs after max expiration

1200 mL

CAN’T be measured by spirometry

51
Q

Forced Vital Capacity (FVC)

A

Volume of air that can be forcibly expired after max inspiration

TV + IRV + ERV = (F?)VC

4500 - 5000 mL

52
Q

Total Lung Capacity (TLC)

A

sum of all 4 lung volumes

VC + RV = TLC

5700 - 6000 mL

CAN’T BE MEASURED by spirometry

53
Q

FEV1 = Forced Expiratory Volume

A

Volume of air that is measured during first second expiration

54
Q

FEV1:FVC ratio

A

% of FVC that can be expired in 1 second

Normal = 70 - 90%

Average = 85%

55
Q

FEV1:FVC in obstructive disease

A

decreases (<70%)

56
Q

FEV1:FVC in restrictive disease

A

increases (>90% or no change)

57
Q

Minute Ventilation (Ve)

A

volume of air expired in 1 minute

Respiratory Rate (RR) x Tidal Volume (TV)

@ Rest = 6 L/min

12 breaths/min x 500 mL

58
Q

How can you increase Minute Ventilation?

A

Increase RR or Increase TV

59
Q

Maximum minute Ventilation (Max Ve)

A

max volume of air moved in/out of lungs during max exercise

measured during stress test

will be 60-70% of Max Voluntary Ventilation (MVV)

60
Q

Maximum Voluntary Ventilation (MVV)

A

max volume of air that can be moved in and out of lungs in 60 seconds

measure for 15 s then x 4

usually higher than Max Ve

61
Q

How would you expect MVV to change in a pt that has an obstructive disease

A

will be 40% of expected normal for their size/weight/sex

62
Q

Is ventilation a limited factor of exercise?

A

No, Max Voluntary Ventilation is 25% higher than exercise ventilation

63
Q

Forced Expiratory Flow Rate (FEF25-75%) aka max midexpiratory flow rate (MMEFR)

A

middle portion of FEV

64
Q

What is the relationship between exercise and lung volumes/capacities?

A

measures of lung volumes/capacities are a poor predictor of athletic performance/fitness

but is useful in predicting disease/dysfunction

65
Q

What population will benefit more from exercise?

A

people w/ pulmonary diseases will see beneficial effect on static/dynamic lung volumes

66
Q

Clinically what will a change in FVC suggest?

A

reduced FVC suggests restrictive disease

67
Q

Clincially what will change in FEV1:FVC ratio suggest?

A

< normal value suggests obstructive disease

> normal value suggests restrictive disease

68
Q

Clinically what will a change in FEV25-75% suggest?

A

< normal can be early indicator of obstructive disease

low w/ normal FEV1 associated w/ asthma severity in kids

69
Q

Clnically what will a change in TLC suggest?

A

> normal suggests obstructive disease

< normal suggests restrictive disease

70
Q

Clinically what will a change in MVV suggest?

A

suggested to represent “strength”

Pathophysiology Thorax (5 decks)

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