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Physiology Test 3 > Resp- Lecture 3&4 > Flashcards

Resp- Lecture 3&4 Flashcards

1
Q

Dalton’s Law of Partial Pressure states:

A

In a mixture of gasses each gas exerts a partial pressure proportional to its concnetration in the mixture

N is 79%*760 mmHg= 600 mmHg Pn2

O2 is 21%* 760 mmHg= 160 mmHg

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2
Q

What does A stand for? a?

A

A=alveolus

a is for arterial

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3
Q

Alveolar gas equation?

A

pAO2= FiO2 x (760-47)- pACO2/R

  • pAO2= Partial pressure of alveolar O2
  • FIO2= Fractional concentraiton of o2
  • 760= total barometic pressure (local)
  • 47= partial pressure water vapor in alveolus
  • pACO2= alveolar partial pressure of CO2
  • R= respiratory quotient (RQ)<– will be given, typically 0.8 BMR
    • RQ= amount of CO2 generate/o2 molecule used
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4
Q

What are nitrogen levels like along respiratory tract?

A

Nitrogen is major component and does not change much

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5
Q

What happens to O2 partial pressure once in trachea?

A

Air automatically becomes saturated with water vapor, so it takes up some of room available in 760. PP h2o= 47 mmHg and PPO2=150 in trachea

21/100*760= 159.6 ppO2 at room air

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6
Q

What are partial pressures like in alveolus?

A
  • pO2= 100 mmHg
  • pH2O= 47 mmHg
  • pCO2= 40 mmHg
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7
Q

What are partial pressures like in artery?

A
  • pO2= 95 mmHg
  • pCO2= 40
  • pH2O=0
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8
Q

What is difference between pAo2 and pao2? What is this called?

A

Alveolar-arterial gradient. Typically 5-10 mmHg

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9
Q

What is primary reason for a-a gradient?

A

Return of deoxygenated blood to Left atrium from bronchial vasculature

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10
Q

When might alveolar-arterial gradient increase?

A

When there is a diffusion problem

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11
Q

Normal tidal volume?

A

500 mL

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12
Q

Normal anatomical dead space?

A

150 mL

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13
Q

Alveolar ventialtion flow?

A

5250 mL/min

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14
Q

What is pulmonary capillary blood flow?

A

70 mL/beat; 70 beat/min

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15
Q

Pulmonary blood flow?

A

5000 mL/min

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16
Q

What is minute ventilation?

A

TV x RR

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17
Q

What is vita capacity?

A

IRV + TV + ERV

inspiratory reserve volume + tidal volume+expiratory reserve volume

(everything you can move, full exertional effort)

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18
Q

What is inspiratory capacity?

A

IRV +TV

Everything inhaled from rest.

Inspiratory reserve volume +tidal volume

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19
Q

What is functional residual capacity?

A

ERV + RV

Everything left in lungs

Expiratory reserve volume + residual volume

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20
Q

Total lung capacity is?

A

IRV + TV + ERV+ RV

Everything!

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21
Q

Can you measure RV by spirometry?

A

No

Any value that includes residual value cannot be measure by simple spirometry (FRC, RV)

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22
Q

What is forced vital capacity?

A

Forcing VC out quickly. Value ends up a little less than VC (you get less air out when forced)

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23
Q

What is anatomic dead space?

A

Volume of conducting airways (150 mL)

  • Can be measured by measuring N2 concentraiton by “washout” using 100% o2
  • Measures volume of conducting airways down to midpoint of transition from dead space to alveolar gas
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24
Q

What is physiological dead space?

A
  • Volume of gas that does not participate in gas exchange and does not eliminate CO2
  • Alveolar CO2 equilibrates with arterial blood
    • co2 so soluble and diffuses so fast that pAco2= paco2
    • can be measured by Bohr’s method
  • ​VD =VT x PaCO2 – PECO__2 where PaCO2 is arterial pCO2
    • PaCO2
    • PeCO2= Expired CO2
    • paCO2= arterial co2
    • VT= tidal volumd
    • Vd= volume dead space
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25
Q

Anatomic dead space and physiological dead space should be almost the ____ in healthy people

26
Q

When might physiological dead space be increased?

27
Q

What is helium dilution method?

A
  • Measures communicating gas, or ventilated lung volume
  • Subject connected to spirometer containing a known concentration of helium
    • subject breaths to equilibrate Helium in his lung as well as spirometer
  • Helium is insoluble in blood
  • new helium concnetration measured
  • C1V1= C2 (V1 +V2)
  • C1= concentration helium in jar
  • V1= volume of gas in jar
  • C2= concentration of helium in lung
  • V2= volume in lung= FRC

can measure RV by combining with spirometry

28
Q

How do you assess alveolar ventilation?

A

Alveolar ventilation (Va)= tidal volume- dead space x rate

CO2 concentration in expired gas may be used to measure alveolar ventilation

VCO2= Va x FCO2 x K (constant)

Fractional CO2= % CO2/100

Va= VCO2/pCO2 x K

29
Q

What does total body plethysmography do?

A

Measure volume of chest cavity.

30
Q

If ventilation is halved, CO2 _____

31
Q

Normal Po2 /Pco2 in alveolus?

A

Po2= 100 mmhg

PCO2= 40 mmHg

32
Q

Normal Po2/Pco2 in pulmonary veins?

A

Po2= 100 mmHg

Pco2= 40 mmHg

33
Q

Normal po2/pco2 in pulmonary artery?

A

pO2= 40 mmHg

pco2= 46 mmHg

34
Q

Diffusion of CO2 is ____ faster than O2

35
Q

How do you assess diffusion?

A

Carbon monoxide

  • CO immediatly binds to blood Hgb
  • Concentration in solution doesn’t build up. Always has same delta P
  • Transfer is truly limited by diffusion
  • Allows to evaluate ability of patient to diffuse gases
  • Vgas= A x D( P1-P2)/T
    • Ax Dco (P1co-p2co)/T
    • DLco= (A/T) x Dco
    • DLco= Vco/PAco
36
Q
  1. At high altitudes, alveolar pO2 is reduced and the gradient between air and blood is less, so rise in pO2 along the capillary is relatively
38
Q

How to find ambient O2?

A

21/100 x ambient pressure

39
Q

How to find inspired o2?

A

21/100 x (ambient pressure-water vapor [47])

40
Q

How to find alveolar o2?

A

Inspired o2- (Pco2/RQ)

41
Q

Causes of hypoventilation?

A
  • Drugs
  • Damage to chest wall
  • Weakness R muscles

Increased resistance to airflow

42
Q

What does hyhpoventilation increase?

A

pAco2 and paCO2 (fraction o2 going down so CO2 will take up more space, therefore increase % co2)

43
Q

Diffusion can be limited by?

A

Interstitial disease

44
Q

What is easiest factor to change in fick’s law to influence diffusion?

A

Change in P

  • Increase pO2 in alveolus will increase gradient and increase arterial po2
45
Q

Shunt refers to what?

A
  • Refers to blood that enters arterial system without going through ventilated areas of the lung
    • v/q=0
    • Perfusion without ventilation
  • SHunt fraction

Qs/ Qt = CcO__2__- CaO__2

CcO2 – CvO2

46
Q

Can a shunt be fixed by giving 100% O2?

A

No, shunted blood is not xposed to high concentration of O2

However, giving O2 will increase alveolar O2, but this will not reach the blood

47
Q

What is physiological dead space?

A
  • When an area of lung is ventilated but not perfused
  • Va/Qc= infinity
  • Ventilation without perfusion
48
Q

What is shunt flow?

A

Perfusion without ventilation (shunted blood returning to left heart that has not been exposed to ventilated alveoli)

49
Q

What is a physiological shunt?

A

Alveolar capillaries are perfused in an area of lung that is not ventilated (i.e. blocked aiway)

  • Va/Qc= 0
  • Can also be anatomic
    • ex- blood from bronchopulmonary circulation returning to L heart
    • Contributes to small alveolar to systemic arterial Po2 gradient
50
Q

What could cause V/Q to = infinity?

A

Pulmonary embolism

51
Q

What can cause V/Q to =0?

A

Airway obstruction, shunt

52
Q

What can cause V/Q <1?

53
Q

Normal V/Q is?

54
Q

When could A-a gradient be normal but hypoxemia present?

A

Low inspired O2 (high altitude)

Hypoventilation

Both can be aliveated by providing extra o2

55
Q

When can hypoxemia be present with A-a increased?

A

Diffusion limitation (o2 will help)

Ventilation-perfusion inequality (o2 will help)

Shunt (o2 will not help)

56
Q

Blood flow distribution in Zone one?

A

Blood flow is lowest

Pressure driving blood flow: PA(alveolar)>Pa(arterial) >Pv

57
Q

Blood flow distribution in zone 2?

A

Medium blood flow

Pa> PA> pv

a= arterial

A= alveolar

P= pressure

58
Q

Blood flow distribtuion in zone 3?

A

Blood flow is highest

Pa> Pv> PA

a= arteriole, v= venous

A= alveolar

59
Q

Ventilation/unit volume is ______ at base vs apex

60
Q

Describe the venitlation-perfusion relationship in the lung

A
  • Both blood flow (Q) and ventilation (V) go down moving from bottom to top of lung
  • But Q (flow) goes down faster than V and Q is denominator, so V/Q goes up (as you go up the lung)

Physiology Test 3 (9 decks)

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