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Physiology And Pharmacology Of Systems > Gaseous Diffusion And Transport > Flashcards

Gaseous Diffusion And Transport Flashcards

1
Q

Definition of fractional concentration (FO2/%)

A

The proportion of air that is made up of O2

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2
Q

Definition of partial pressure (PO2)

A

The pressure at which a gas in the air exerts

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3
Q

Definition of barometric pressure (Pb)

A

Total pressure of gases in the atmosphere

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4
Q

Definition of inspired PiO2, FiO2

A

Partial pressure of O2/fractional concentration of O2 in moistened inspired air at the end of the trachea

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5
Q

Definition of alveolar PAO2,FAO2

A

Partial pressure of O2/fractional concentration of O2 in the alveoli

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6
Q

Definition of arterial PaO2/FAO2

A

Partial pressure of O2/fractional concentration of O2 in the arterial blood

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7
Q

Definition of dead space

A

Airway volume with no gas exchange

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8
Q

Definition of anatomic dead space (ADv)

A

All except alveoli and respiratory bronchioles

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9
Q

Definition of physiologic dead space (PDv)

A

Anatomic dead space and areas where gas exchange is dysfunctional

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10
Q

Definition of saturation

A

Depends on how much air has been in contact with the water

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11
Q

Definition of polycythaemia

A

Increase in no of RBCs in the blood

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12
Q

Definition of capacity

A

How much something is capable of carrying

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13
Q

What is Dalton’s Law

A

In a mixture of non reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases

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14
Q

What is Pb at sea level
What is FO2
What is PO2 as a result

A

Pb = 101kPa
FO2 - 0.209
PO2 = 101 x 0.209 =21kPa

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15
Q

How does Pb, FO2, PO2 change at altitude?

A

Pb falls
FO2 doesn’t change
PO2 falls

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16
Q

What is Henry’s Law
What happens when the partial pressure increases
How would you increase partial pressure

A

C = kp

C = conc of dissolved gas at equilibrium
k = solubility
p = partial pressure

Partial pressure increases = more dissolves
Change PP by changing volume

17
Q

Describe the relative solubilities of N2, O2 and CO2

What is the bends?

A 
O2 = 2x more soluble than N2
CO2 = 20x more soluble than O2

If Pb decreases too rapidly (rise to the surface too fast), N2 isn’t breathed out and gas accumulates in blood and joints
Causes severe pain

18
Q

What factors affect PH2O
What is the value of PH2O
How does PH2O affect PAO2

A

Affected by temp and saturation, NOT BY PB

6.3kPa

As you breathe in, air comes into contact with moisture in lungs = 100% saturation

19
Q

In atmospheric air, what is
PO2
PCO2
PH2O

A

PO2
-21

PCO2
-0

PH2O
-var

20
Q

In expired air, what is
PO2
PCO2
PH2O

A

PO2
-16

PCO2
-3.5

PH2O
-var

21
Q

In inspired tracheal air, what is
PO2
PCO2
PH2O

How would you calculate these values

A

PO2
-20

PCO2
-0

PH2O
-6.3

(Pb-PH2O) x FiO2
(101-6.3) x 0.209 =20 ish

22
Q

In alveolar air, what is
PO2
PCO2
PH2O

How would you calculate these values

A

PO2
-13.5

PCO2
-5.3

PH2O
-6.3

PO2 = PiO2 - PACO2/R
13.5 = 20 - 5.3/0.8
23
Q

How do you calculate PAO2 as you cannot measure it directly and why

What is the normal value for R

A

Can’t be measured directly as O2 input and CO2 output are not equal

PAO2 = PiO2 - PACO2/R

R=CO2 production/O2 consumption
R=0.8

24
Q

Describe gas exchange of O2 and CO2 in the pulmonary arteries and veins

What are the PP values in the pulmonary arteries, alveoli, pulmonary vein

What can happen when flow is abnormal/too fast

A

O2 movement powered by PP grad

Pulmonary arteries PO2 = 5.3
Alveoli = 13.5
Pulmonary veins PO2 = 13.5

CO2 diffuses slower than O2 due to increased MW
Solubility is higher equilibrates rapidly

Pulmonary arteries PCO2 = 6.1
Alveoli = 5.3
Pulmonary veins = 5.3

Less time for gas diffusion => hypoxia/hypercapnia

25
Q

Name the 3 capillary layers

A

Alveolar epithelium
Interstitial fluid
Endothelium

26
Q

How would you measure the rate of gas diffusion across the capillary wall

A 
Rate = c∆ x A/x∆ x sol/√MX
Rate = Dlg (PA -Pc)

CO has a v high affinity for haem, none dissolved in blood

Patient inhales CO tracer gas, composition of exhaled gas examined
-If DlCO = 100% => efficient gas transfer

27
Q

How do these factors affect the DlCO

  • Surface area of barrier
  • Thickness of barrier
  • Anaemia
  • Polycythaemia
  • Increasd pulmonary BV in exercise
A

SA

  • reduced in emphesyma, lung resection, reduced venous return
  • Decreased DlCO

Thickness

  • increased in fibrosis, congestive heart failure, vascular diseases
  • decreased DlCO

Anaemia

  • decreased Hb to pick up O2
  • decreased DlCO

Polycythaemia

  • increased Hb to pick up O2
  • increased DlCO

Increased pulmonary BV in exercise

  • Increased effective area
  • increased DLCO
28
Q

Describe how gas exchange occurs between the capillaries and tissues
What problems could occur at the venous end of the capillaries

A

O2 diffuses down the partial pressure gradient
Arterial end = 13.5
Venous end = 5.3

Venous end less likely to receive highly oxygenated blood, if PO2 too low => diffusion slows down => hypoxic tissue

29
Q

Describe how O2 is loaded and unloaded from RBCs
What is the PO2, O2 content, SaO2 in venous blood and arterial blood

What is the Bohr effect?

A

Sigmoid relationship between O2 sats and PP

Venous blood

  • PO2 = 5.3
  • O2 content = 150ml/l
  • SaO2 = 75%

Arterial

  • PO2 = 13.5
  • O2 content = 200ml/l
  • SaO2 = 100%

Bohr effect

  • decreased pH
  • increased pCO2
  • increased temp
  • increased 2, 3 DPG => MORE O2 OFFLOADED
30
Q

What PO2 is good in venous blood?

At what values should we be concerned and why?

A

PO2 in venous blood > 8 => good oxygenation of tissues

PO2 < 8 => O2 offloads too quickly (on steepest part of curve), tissue on venous side => hypoxic

31
Q

Describe how altitude affects

  • O2 capacity
  • Pb
  • PiO2
  • PaO2
  • SaO2
A

O2 capacity
-normal

Pb
-decreased

PiO2
-decreased

PaO2
-decreased

SaO2
-decreased

32
Q

Describe how anaemia affects

  • O2 capacity
  • Pb
  • PiO2
  • PaO2
  • SaO2
A

O2 capacity
-decreased due to less Hb

Pb
-normal

PiO2
-normal

PaO2
-normal

SaO2
- normal

33
Q

What is the difference between capacity, content and saturation?

A

Capacity
-how much O2 a RBC can carry

Content
-How much O2 a RBC is carrying

Saturation
-Percentage of Hb carrying O2

Physiology And Pharmacology Of Systems (22 decks)

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