Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

FHB II Pulmonary/Renal > Pulmonary 7: Gas transport > Flashcards

Pulmonary 7: Gas transport Flashcards

1
Q

In what two forms is O2 carried in the blood?

A
  1. dissolved

2. bound to hemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is dissolved oxygen measured clinically?

A

measured clinically as PaO2 (blood gas analysis)

the amount that can be dissolved follows Henry’s Law of gas solubility (the concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution. C= kHP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Provide the following values in regards to dissolved oxygen (measured clinically as PaO2).

Per 1mmHg of PO2
normal blood (PaO2 100mmHg)

What is normal O2 consumption?

A

Per 1 mmHg of PO2 → 0.003 mL O2 / 100 mL of blood

normal blood (PaO2 100 mmHg) → 0.3 mL O2/100 mL

3 mL O2/L x cardiac output (5 L/min) = 15 mL O2/min

Normal O2 consumption (VO2) ~ 250 mL/min

This obeys Henry’s law, that is, the amount dissolved is proportional to the
partial pressure. For each mm Hg of PO2, there is 0.003 mlO2/100 ml of blood. Thus, normal arterial blood with a PO2 of 100 mm Hg
contains 0.3 mlO2/100 ml.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Draw a dissolved oxygen curve. PO2 (mmHg) on horizontal axis, and % Hb saturation and O2 concentration on vertical axes.

Show dissolved, total blood and hemoglobin bound oxygen concentration at a hemoglobin concentration of 15g/dL

A

Slide 6

  • small percentage of total O2
  • under normal conditions, almost negligible
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe Hemoglobin (its structure).

A

4 heme groups containing (Fe 3+) - O2 binding sites

4 polypeptide chains
2 alpha-globin chains, 2 B-globin chains = HbA

Binding/dissociation of O2 occurs in milliseconds and 
changes light absorption of Hb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How is the hemoglobin structure different in children less than a year old.

A

Children HbF – 2 alpha-globin and 2 gamma-globin chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the oxyhemoglobin dissociation curve show?

Discuss its shape and what it means.

A

Shows the relationship between the partial pressure of O2 in blood and the percentage of Hgb binding sites that are occupied by oxygen molecules (percent saturation)

Sigmoid shape of HbO2 curve reflects the four-stage cooperative loading of oxygen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

At what PO2 is HbA (adult hemoglobin) 50% saturated? 90% saturated? 98% saturated?

What is P50? What happens to P50 if the dissociation curve shifts L or R?

(Draw)

A

Slide 8.
50% saturated at PO2 of 27mmHg, 90% saturated at 60mmHg and 98% saturated at 100mmHg.

The P50 is the partial pressure at which Hgb is 50% saturated with O2. When the O2 dissociation curve shifts to the right, P50 increases. When the curve shifts to the L, P50 decreases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe how Hb saturation changes at partial pressures above 60mmHg.

How does it change at pressures below 60mmHg?

Describe the significance of the shape of the curve, what does the flat portion signify?

A

At partial pressures > 60 mmHg:
small changes in Hb saturation

—normal O2 transport to organs/cells

At partial pressures 60 mm Hg) is that a drop in PO2 over a
wide range of partial pressures (100 to 60 mm Hg) has
only minimal effect on Hgb saturation, which remains
at 90% to 100%, a level sufficient for normal O2 transport and delivery.

shape shows the dependence of Hgb saturation on PO2 (esp. at partial pressures lower than 60mmHg)

flat portion (larger than 60mmHg) is that a drop in PO2 over a wide range of partial pressures (100-60mmHg) has only a minimal effect on Hgb saturation which remains at 90-100% (sufficient level for O2 transport and delivery) …flat portion means a large amount of O2 is released from Hgb with only a small change in PO2 which facilitates the release and diffusion of O2 into tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Which physiological factors will shift the oxyhemoglobin dissociation curve to the L? to the R?

(Discuss increases/decreases in temperature, PCO2, 2,3 DPG, or pH)

Is this an increase or decrease in P50?

A

decreased P50 (increased affinity)

  • decreased temperature
  • decreased PCO2
  • decreased 2-3, DPG
  • increased pH

Increased P50 (decreased affinity)

  • increased temperature
  • increased PCO2
  • increased 2,3-DPG
  • decreased pH

Slide 9

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Draw a dissociation curve (O2 + hemoglobin) and CO + hemoglobin. Explain the difference.

What happens in the presence of small amounts of CO?

A

Affinity of CO for Hb
> 200 times greater
than the affinity of O2

At 1 mmHg CO: all binding
sites are occupied

In the presence of 
small amounts of CO:
Affinity for O2 is 
enhanced and unloading
prevented
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What would a PaO2 of 60mmHg indicate?

A

hypoxemia… 80

60mmHg is v dangerous… coordinates with a 90% SO2 (oxygen saturation…%saturation of Hb?)

See slide 11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How many mL of O2 can 1g of Hb bind?

How much Hb/O2 is there in normal blood?
Calculate O2 extrated from the blood.

A

1 g of Hb can bind 1.34 mL of O2 = O2 capacity

Normal blood (15g Hb/100mL) = 20.1mLO2/100mL =SO2 100%

at 19.5mLO2/100mL - SO2% is 97
at 15.1 mLO2/100mL- SO2% is 75

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Given a change from 97% saturated to 75% how much was dropped off to blood?

Calculate O2 extracted from the blood.

A

19.5-15.1= 4.4mL O2/100mL x CO (5L/min) = 220mL O2/min

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Given normal blood (15g Hb/100 mL) = 20.1 mL O2/100 mL = SO2 100%

What would be the values for an anemic patient? Where on the saturation curve would an anemic person be?

A

Anemic patient (7.5g Hb/100 mL) = 10.1 mL O2/100 mL = SO2 100%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does oxygen content depend on?

Describe the relationship between Hb saturation and Hb concentration.

A

Oxygen content depends on the oxygen transport capacity of blood =Hb concentration.

Hb saturation is independent of the Hb concentration.

17
Q

Draw blood oxygen content and saturation curves at Hb= 20, Hb =15 and Hb=10

A

Slide 14

Effects of anemia and polycythemia on O2 concentration and saturation.
In addition, the broken line shows the O2 dissociation curve when one-third of the normal hemoglobin is bound to CO. Note that the curve is then shifted to the left. (West p. 80)

18
Q

Describe the curved shape of the O2 dissociation curve:

What does the flat upper portion mean? The steep lower part?

A

The curved shape of the O2 dissociation curve has several physiological advantages.

The flat upper portion means that even if the PO2 in alveolar gas falls somewhat, loading of O2 will be little affected. In addition, as the red cell
takes up O2 along the pulmonary capillary, a large partial pressure difference between alveolar gas and blood continues to exist when most of
the O2 has been transferred. As a result, the diffusion process is hastened.

The steep lower part of the dissociation curve means that the peripheral tissues can withdraw large amounts of O2 for only a small drop in capillary PO2. This maintenance of blood Po2 assists the diffusion of O2 into the tissue cells.

19
Q

When is cyanosis caused?

A

Because reduced Hb is purple, a low arterial O2 saturation causes cyanosis

20
Q

What are the three forms that CO2 is carried in the blood?

A
  1. dissolved
  2. as bicarbonate
  3. as carbamino compounds with proteins
21
Q

How is dissolved CO2 measured clinically?

What are the values of 1mmHg of PCO2?

(How does this compare to O2)

A
  • is measured clinically as PaCO2 (blood gas anaylsis)
  • amount that can be dissolved follows Henry’s Law

(C=KHP, concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution)

per 1mmHg PCO2– 0.067 mL CO2/100mL blood
=20x more than O2

22
Q

Write out the equation for the formation of bicarbonate.

A

CO2+ H2O – H2CO3 — H+ + HCO3-

HCO3 is bicarbonate

23
Q

Describe the bicarbonate present in plasma and in erythrocytes.

What is the hydrogen equilibrium constant at 25 degrees C (Kh)?

A

in plasma:
slow conversion to carbonic acid
majority exists as CO2

Kh is [H2CO3]/[CO2] which is approx. 1.7 x 10^-3 in water

in erythrocytes: (carbonic anhydrase (CA)

24
Q

What is the most important protein?

A

globin of hemoglobin (carbaminohemoglobin)

Hb can bind more CO2 than HbO2

Slide 18

Carbamino compounds are formed by the combination of CO2 with terminal
amine groups in blood proteins. The most important protein is the globin of hemoglobin: Hb·NH2 + CO2–Hb·NH·COOH, giving carbaminohemoglobin.
This reaction occurs rapidly without an enzyme, and reduced Hb can bind more CO2 as carbaminohemoglobin than HbO2. Thus, again, unloading
of O2 in peripheral capillaries facilitates the loading of CO2, whereas oxygenation has the opposite effect

25
Q

Review mechanisms of CO2 transport in the blood. Slide 19.

What is the predominant mechanism by which CO2 is transported from tissue cells to the lung?

A

Slide 19.

Predominant mechanism by which CO2 is transported from tissue cells to the lung is in the form of HCO3-
RBC

26
Q

Describe CO2 transport in the blood.

How much is dissolved?
How much as carbamino?
How much is HCO3-?

A

10% dissolved
20-30% as carbamino
60-70% as HCO3-

27
Q

Describe the role of erythrocytes in CO2 transport?

A

erythrocytes are as crucial for CO2 transport in the blood as they are for oxygen transport in the blood.

28
Q

What is a chloride shift and what is the purpose?

A

When intracellular H+ and HCO3- increase in erythrocytes, [HCO3-] diffuses out and Cl- in to maintain electrical neutrality =chloride shift.

Slide 20

29
Q

Describe what happens if there is an increase in H+ ions.

A

ph decreases, CO2 increases
Right shift of curve (P50 increases)

facilitates O2 delivery

Hb carries more CO2 than HbO2 (Haldane effect)

Some H+ are bound by Hb (less acidic than HbO2)

facilitates CO2 unloading.

30
Q

Describe how the dissociation curves for O2 and CO2 differ (while focusing mainly on CO2). What has a major effect on the CO2 dissociation curve?

Will deoxygenated Hgb or oxygenated Hgb have a higher affinity for CO2? What are the implications for this?

Explain the Haldane effect. When is it reversed?

Will the CO2 dissociation shift curve Left or R (and in arterial or venous blood) to show this effect?

A

In contrast to O2, the dissociation curve for CO2 in
blood is linear and directly related to PCO2.
The degree of Hgb saturation with O2 has a major
effect on the CO2 dissociation curve. Although O2 and
CO2 bind to Hgb at different sites, deoxygenated Hgb
has greater affinity for CO2 than oxygenated Hgb does.
Thus, deoxygenated blood (venous blood) freely takes
up and transports more CO2 than oxygenated arterial
blood does. The deoxygenated Hgb more readily forms carbamino compounds and also more readily binds free H+ ions released during the formation of HCO3-.

The effect of changes in oxyhemoglobin saturation on
the relationship of CO2 content to PCO2 is referred to
as the Haldane effect and is reversed in the lung when
O2 is transported from the alveoli to red blood cells.
This effect is illustrated by a shift to the left in the CO2
dissociation curve in venous blood as compared with
arterial blood.

31
Q

Describe the Haldane effect graphically.

(CO2 partial pressure on horizontal axis and CO2 concentration on vertical axis)

second graph- PCO2 on horizontal axis and CO2 concentration on vertical axis.

(What is Haldane shift and Bohr shift)

A

Slide 22.

the lower the O2 saturation, the larger the CO2 concentration

In pulmonary capillaries where the environmental PO2 is high, the presence of the oxygen decreases the affinity of hemoglobin for CO2 and assists in the unloading of CO2 from the blood to the alveolar spaces. This effect is called the Haldane shift.

In tissue capillaries where the environmental PCO2 is high, the presence of carbon dioxide decreases the affinity of hemoglobin for O2 and assists in the unloading of O2 from the blood to the tissue spaces. This effect is called the Bohr shift.

32
Q

Describe the shape of the CO2 dissociation curve (and how differs from O2 curve) What does the CO2 curve account for?

What does the position of CO2 curve depend upon?

At a given PCO2 describe how much O2 and CO2 venous blood can hold in comparison to arterial blood. What is the significance of this?

Draw.

A

Slide 23.
The CO2 dissociation curve shows the dependency of the total CO2 content of the blood (mL CO2/dL) as a function of PCO2. The shape of the CO2 dissociation curve is hyperbolic (without a flat-top), unlike the oxygen dissociation curve which is sigmoid (with a flat-top).
The curve accounts for all three forms of CO2 (dissolved, carbamino CO2 and bicarbonate CO2.)

Position of CO2 dissociation curve depends upon the prevailing PO2. At any given PCO2, venous blood (at PO2=40mmHg) can hold more carbon dioxide than arterial blood (at PO2= 95mmHg). This means that an increase in PO2 shifts the CO2 dissociation curve to the right. Or any increase in PO2 causes the CO2 affinity of blood to decrease.

33
Q

Describe tissue hypoxia.

Draw three scenarios in which there is adequate oxygen delivery, critical oxygen delivery, and inadequate (cap-tissue-cap against PO2 mmHg)

O2 consumption continues at same rate until what PO2 value?

A

a condition in which insufficient oxygen is available to maintain adequate aerobic metabolism.

O2 consumption continues at the same rate until PO2 is less than 3mmHg

34
Q

Describe hypoxic hypoxia. What is a typical clinical symptom?

A

Diseases/conditions with decreased PaO2 leading to insufficient O2 delivery to tissues

  • suffocation
  • COPD
  • pulmonary fibrosis

typical clinical symptom- cyanosis bc of lack of oxygen and increased deoxyhemoglobin (approx 6 g/dL of deoxyhemoglobin are required to appear cyanotic..thus in patients with anemia cyanosis may not occur despite hypoxic hypoxia)

35
Q

Describe circulatory (stagnate) hypoxia).

A

reduced blood flow to tissues, e.g. vascular disease or cardiac insufficiency

36
Q

Describe anemic (hypemic) hypoxia.

A

Inability of blood to carry sufficient oxygen

  • anemia
  • CO poisoning
37
Q

Describe histotoxic hypoxia.

A

Inability of cell to utilize oxygen

-poisoning (cyanide, sodium azide)

FHB II Pulmonary/Renal (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions