Gas Exchange

Question 1

External Respiration

Answer 1

Pulmonary ventilation (Breathing)
Pulmonary Gas Exchange

Question 2

Components of Respiration

Answer 2

External Respiration
Internal Respiration
Transport of Gases through blood

Question 3

Internal Respiration

Answer 3

Systemic tissue gas exchange

Cellular Respiration

Question 4

Respiratory Cycle-Inspiration

Answer 4

During inspiration, the diaphragm contracts, increasing the volume of the thoracic cavity. This increase in volume results in a decrease in pressure, which causes air to rush into the lungs.

Question 5

Respiratory Cycle-Expiration

Answer 5

During expiration, the diaphragm returns to an upward position, reducing the volume in the thoracic cavity. Air pressure thus increases, forcing air out of the lungs.

Question 6

Partial Pressure of Gases

Answer 6

Partial Pressure of gases is the pressure exerted by a gas in a mixture of gases or liquids

Question 7

Law of Partial Pressure

Answer 7

Dalton’s Law

The partial pressure of a gas in a mixture will equal the total pressure if that gas

Question 8

Arterial Blood

Answer 8

PO2 and PCO2 equal alveolar PO2 and PCO2

Due to continuous ventilation PO2 and PCO2 should remain relatively constant

Question 9

Factors that Determine Diffuse of O2 into blood

Answer 9

1) O2 pressure gradient between alveolar air and blood
2) Total functional surface are
3) Respiratory minute ventilation
4) Alveolar ventilation versus deadspace ventilation

Question 10

Structural Factors that Facilitate Oxygen Diffusion from the Alveolar Air to the Blood

Answer 10

The walls of the alveoli and capillaries form only a very thin barrier for gases to cross. As little as half a micron.
The alveolar and capillary surfaces are large
The blood is distributed through the capillaries in a thin layer so that each red blood cell comes close to alveolar air.

Question 11

Bohr Effect

Answer 11

Increased PCO2 at the tissue level will decrease the affinity between oxygen and Hb (dumping of O2 at the tissue level)

Question 12

Haldane Effect

Answer 12

Increased CO2 loading caused by a decrease in PO2 (increase loading of CO2) at the tissue level

Question 13

Rate of Diffusion

Answer 13

〖Diffusion 〗_gas= [(A x Cs)/T ] x ∆P
	According to Fick’s Law the membrane diffusion rate is affected by
	Surface Area (A)
	Solubility of Gas (Cs)
	Membrane Thickness (T)
	Partial Pressure (∆P)

Question 14

Diffusion Rate and Surface Area

Answer 14

As surface area increases there will be a greater diffusion rate

Question 15

Diffusion Rate and solubility coefficient

Answer 15

As solubility coefficient increased there will be an increase in diffusion rate

Question 16

Diffusion Rate and Partial Pressure Gradient

Answer 16

As the partial pressure gradient increases there is an increase in diffusion rate

Question 17

CO2 Diffusion versus O2

Answer 17

CO2 will diffuse 20 times faster than O2 due to the fact that it has a higher solubility (heavier molecule)

Question 18

Graham’s Law

Answer 18

Gas diffusion rate is inversely proportional to the square root of the gram molecular weight (density)
the lighter the gas the faster the diffusion rate

Question 19

Henry’s Law

Answer 19

Gas diffusion is directly proportional to the partial pressure
Basis of O2 therapy
Greater pressure=greater diffusion

Question 20

Capillary Blood Transit

Answer 20

Capillary Transit Time=0.75 sec

Alveolar-Capillary Equilibrium-Within the first 0.25

Question 21

Perfusion and Diffusion Limitations to O2 transfers

Answer 21

Decreased or increased blood flow

Thickened alveolar blood flow

Question 22

CO Diffusion

Answer 22

Limited diffusion due to a strong affinity to Hgb

PP doesn’t rise easily

Question 23

N2O Perfusion

Answer 23

Perfusion is limited

Equilibrium pressure is reached quickly, therefore more blood is needed to accept more N2O

Question 24

Oxygen Diffusion Path Length

Answer 24

From alveolar gas to red blood cells

The path is less than 1/2 micron

Question 25

Pathologies that increase O2 Diffusion

Answer 25

Pulmonary Fibrosis
Interstitial Edema
Alveolar Fluid
Interstital Fibrosis

Question 26

Measuring Diffusion Capacity

Answer 26

Done through the Single-Breath CO Diffusion Test (DLCOsb)
DLCO=mL CO transferred to the blood/min
Mean PACO=Mean PCCO

Question 27

Normal Values in Diffusion Capacity

Answer 27

20-30mL/min/mmHg
DLO2=DLCO x 1.23=~32mL/min/mmHg
Unit of diffusion is opposite of resistance

Question 28

Conductance

Answer 28

Flow/pressure

Question 29

Factors that Affect DLCO

Answer 29

Body Size
Age
Lung Volume
Exercise
Body Position (will be 15-20% higher in supine)
Alveolar PO2 and PCO2
Alveolar PCO
Hemoglobin Concentration
Pulmonary Diseases (decrease total AC Membrane)

Question 30

Water Balance in Lungs

Answer 30

The Pulmonary capillary is a semi-permeable membrane
Due to the net outward pressure there will always be movement of fluids out of the capillaries
Lymphatic vessels will immediately drain the fluid coming out of the interstitial , which is important to make sure that fluid does not enter the alveoli
Due to the fact that the alveolar wall is so thin any increase in interstitial pressure will rupture the alveoli

Question 31

Oncotic Pressure

Answer 31

Influence of proteins on osmotic pressure
the effect of of filtration on protein concentration will also serve as a mechanism to limit capillary filtration
Normal tissue oncotic pressure is ~5mmHg

Question 32

Tissue (Interstitial) Oncotic Pressure (Πi)

Answer 32

The oncotic pressure of interstitial fluid will interstitial protein concentration and reflection coefficient of the capillary wall
The more permeable the capillary barrier is to protein the higher interstitial oncotic pressure
Pressure is also determined by amount of fluid filtration into interstitum (increase filtration will decrease interstitial protein concentration and reduce osmotic pressure)

Question 33

Water Imbalance-Pulmonary Edema

Answer 33

Increased hydrostatic pressure (fluid pushed out of capillaries) which can be cause by: Left ventricular failure, fluid overload,
Increased Capillary Permeability which can be caused by: non cardiac pulmonary deem
Decreased Plasma Oncotic Pressure: starvation, hemodilation, proteinuria
Lymphatic Insufficiency: Tumour, compression, trauma