Chapter 6 Oxygen Transport 1307

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Normal CaO2 is

20 mL/dL

The quantity of oxygen that dissolves in plasma is determined by the

PAO2 to which plasma is exposed.

Mixed Venous Oxygen Saturation (SvO2)

Saturation of venous blood in RA

Hyperthermia (exercise or fever)

Shift to the RIGHT Enhances release of O2 at the cellular level

CaO2=

[(Hb x 1.34)(SaO2)] + (PaO2 x 0.003)

Increase in SvO2 indicates that C(a-v)O2, VO2, and O2ER are ____

decreasing

> 30 % is ____

life threatening

A small amount of CO ties up a lot of hemoglobin and

prevents oxygen molecules from binding to hemoglobin

At normal body temperature:

0.003 mL of O2 will dissolve in 100 mL (deciliter) of blood for every 1 torr of PO2

Each gram of Hb is capable of carrying ___ mL of oxygen

1.34

Steep part of curve

10-60 torr, O2 combines rapidly with Hb as the PaO2 increases

5 mL of O2 are needed from each ___mL blood for normal tissue metabolism

100

Total Oxygen Delivery average

1000 mL O2 / min

0.3 mL of O2 is dissolved in every ____ of blood plasma

100mL

Hb F is gradually replaced with Hb A during the first ___ months of life

12

Normal Hb for an Adult Female

12-15 g/dL

Normal Hb for an Adult Male

14-16 g/dL

Normal CvO2 is

15 mL/dL

What is the normal CaO2 value?

16-20 mL/dL, vol% or mL/100 mL of blood

Hemoglobin's affinity for CO is ___ greater than O2

210

Normal Oxygen Concentration Ratio (O2ER)

25%

Normal Oxygen Consumption is

250 mL/min

Each red blood cell contains ___ million hemoglobin molecules

280

Normal Anatomic Shunt is ___% of Cardiac Output

3

Moderate Hypoxemia

40-59 torr

Normal C(a-v)O2 is

5 mL/dL

Flat part of curve

60-100 torr; increases in PaO2 have little effect on SaO2

Mild Hypoxemia

60-79 torr

Under normal circumstances a person's hemoglobin returns to the alveoli ~____% saturated with oxygen

75

Normal Mixed Venous Oxygen Saturation (SvO2)

75% is normal (65% is acceptable)

The PaO2 can drop from 100 to 60 torr and Hb will still be ___% saturated with O2 (____)

90;suggests a strong affinity

Hypoxemia

Abnormally low arterial oxygen tension (Low PaO2)

Absolute Shunt is caused by

Alveolar collapse or atelectasis Alveolar fluid accumulation Alveolar consolidation (fluid, blood, infection)

Relative Shunts are caused by

Alveolar hypoventilation Ventilation/Perfusion mismatch: Chronic emphysema, bronchitis, asthma and excessive airway secretions Alveolar-capillary diffusion defects Pulmonary fibrosis, pulmonary edema

Total Oxygen Delivery (Do2)

Amount of oxygen delivered (or transported) to peripheral tissues is dependent upon: Body's ability to oxygenate the blood Hemoglobin concentration Cardiac output (QT)

Oxygen delivery to the tissue cells decreases if there is decline in:

Blood oxygenation (PaO2) Cardiac output Hb concentration

The impact of changes in blood pH on hemoglobin's affinity for oxygen is called the

Bohr effect

How is a Mixed Venous Oxygen Saturation (SvO2) obtained?

By an indwelling (Swan-Ganz) pulmonary artery catheter

O2ER=

C(a-v)O2/CaO2

PaO2 falls below 60 torr

Decrease in amount of oxygen bound to hemoglobin Quantity of O2 delivered to tissue cells may be significantly reduced

Factors that Increase Oxygen Concentration Ratio

Decreased cardiac output Increased oxygen consumption Anemia Decreased arterial oxygenation

Hemoglobin S or "Sickle Cell Anemia"

Deoxygenated Hb changes RBC shape to crescent or sickle form; tendency to form thrombi

Arterial-Venous Oxygen Content Difference C(A-V)O2

Difference between CaO2 and CvO2

Oxygen is transported in blood in two forms:

Dissolved oxygen molecules in blood plasma Chemically bound to hemoglobin (Hb) within the erythrocyte (RBC)

Methemoglobin

Drugs and chemicals (nitric oxide) change iron molecule from ferrous state to ferric state, so it cannot combine with O2 for transport

Factors that increase Arterial-Venous Oxygen Content Difference C(A-V)O2

Exercise Seizures Shivering Hyperthermia

Factors that increase Oxygen Consumption

Exercise Seizures Shivering Hyperthermia

Four heme (iron) groups on each Hb molecule, bonded and enfolded in:

Globin (complex protein) made of four linked amino acid chains

Shift to the Right: Oxyhemoglobin Dissociation Curve

Hb affinity for O2 decreases (Hb is less saturated at a given PO2) and oxygen unloading at the cellular level is enhanced

Shift to the Left: Oxyhemoglobin Dissociation Curve

Hb affinity for O2 increases (Hb is more saturated at a given PO2) and oxygen loading onto Hb molecule in the lungs is enhanced

If all 4 Heme groups on a hemoglobin molecule bind with four O2 molecules,

Hb is considered to be 100% saturated with O2 "Oxyhemoglobin"

Deoxyhemoglobin

Hemoglobin not bound to O2

Oxyhemoglobin Dissociation Curve

Illustrates the percentage of Hb that is chemically bound to O2 (saturation) at any specific PaO2

Factors the decrease Arterial-Venous Oxygen Content Difference C(A-V)O2

Increased QT Skeletal muscle relaxation Peripheral shunting (sepsis, trauma) Certain poisons (cyanide, prevents cellular metabolism) Hypothermia

Factors that decrease Oxygen Concentration Ratio

Increased cardiac output Skeletal muscle relaxation Peripheral shunting Poisons Hypothermia Increased Hb Increased arterial oxygenation

Fetal Hb (Hb F)

Increases hemoglobin's affinity for O2 allowing for better transfer of maternal O2 across placenta to the fetus

What happens with a Left Shift on the Oxyhemoglobin Dissociation Curve?

Loading of O2 at the lungs is enhanced and Unloading of O2 at the Tissues

Is the Oxyhemoglobin Dissociation Curve a linear relationship?

No it is an S Curve

2,3-BIPHOSPHOGLYCERATE (BPG)

Organic phosphate and by-product of anaerobic glycolysis found in the RBC

Total O2 content (CaO2) in 100 mL of blood consists of:

Oxygen dissolved in the plasma + Oxygen bound to hemoglobin

P50 ON Oxyhemoglobin Dissociation Curve

Partial pressure at which the Hb is 50% saturated with O2 (2 oxygen molecules on each Hb molecule) (Normal P50 is 27 torr)

Shunt Equation

Percent of shunted blood when compared to Cardiac Output

Absolute Shunt responds ____to oxygen therapy (refractory)

Poorly

Pulmonary Shunt

Portion of the cardiac output that moves from the RIGHT side of heart to LEFT side of heart without being exposed to alveolar oxygen

Relative Shunt

Pulmonary capillary perfusion exceeds alveolar ventilation

Hypothermia

Shift to the LEFT O2 demand at the cold tissues sites is decreased

Factors that decrease Oxygen Consumption

Skeletal muscle relaxation Peripheral shunting Certain poisons Hypothermia

Blood pH fluctuations cause variations in the shape of the hemoglobin molecule (what specific part?)

The Globin Portion

Henry's Law:

The amount of gas that dissolves in a liquid (blood plasma) is proportional to its partial pressure.

Oxygen Consumption

The amount of oxygen consumed by the peripheral tissues in 1 min (VO2)

Oxygen Concentration Ratio (O2ER)

The amount of oxygen extracted by the peripheral tissues divided by the amount of oxygen delivered to the peripheral cells

When PaO2 is within normal limits (80 to 100 torr), a shift of the oxyhemoglobin dissociation curve to the right or left does NOT significantly affect hemoglobin's ability to transport oxygen to the peripheral tissues, because shifts in this pressure range occur where on the curve?

The flat part/safe space

Venous Admixture

The mixing of shunted, non-reoxygenated blood with re-oxygenated blood in the pulmonary venous system

When PaO2 falls below the normal range (60 or 80), a shift to the right or left can have a remarkable effect on hemoglobin's ability to pick up and release oxygen, because shifts in this pressure range occur where on the curve?

The steep part

Normal Physiologic Shunts(all deoxygenated):

Thebesian venous drainage into the LA Bronchial venous drainage Underventilated alveoli relative to pulmonary blood flow (zone 1)

Anatomic Shunts

When blood flows from Right side of heart to Left side of the heart without coming into contact w/alveolus

Abnormal Hemoglobin

When the number, sequence, or spatial arrangement of globin chains is altered, hemoglobin will be abnormal

In a normal Anatomical Shunt deoxygenated blood bypasses the alveoli and enters the pulmonary vascular system via ___and Coronary blood enters LA via ____

bronchial venous drainage; Thebesian veins

Most O2 that diffuses from the alveoli into pulmonary capillary blood moves rapidly into erythrocytes and

chemically binds to hemoglobin (Hb) molecules

Examples of Abnormal Anatomic Shunts:

congenital heart disease, intrapulmonary fistula, vascular lung tumors

Most pulse oximeter measurements below 70% are considered

inaccurate and unreliable

Hypoxia ___ 2,3 BPG levels

increases

Decrease in SvO2 indicate that C(a-v)O2, VO2, and O2ER are ___

increasing

10-20 % indicates ___

intrapulmonary abnormality

20-30 % indicates significant ___

intrapulmonary disease

Oxygen transport between the lungs and body tissue cells

is a function of the blood and the heart

COHb impedes oxygen delivered to body tissues by shifting the curve to the ____

left

Shunt % < 10 is___

normal

If PaO2 within normal range----small right to left shift on Oxyhemoglobin Dissociation Curve is

not clinically significant.

At center of each of the four heme groups, the iron molecule can combine with one O2 molecule in an easily reversible reaction to form

oxyhemoglobin

Factors that Shift the Oxyhemoglobin Dissociation Curve

pH H+ CO2 levels Body Temperature 2,3 DPG Hb F COHb

As hydrogen ion concentration increases:

pH decreases (acidotic) Shifts curve to the RIGHT Hb affinity for O2 Enhances the unloading of O2 at cellular level

As hydrogen ion concentration decreases

pH increases (alkalotic) Shifts curve to the LEFT Hb affinity for O2 Enhances the loading of O2 onto Hb

At a normal PaO2 of 100, Hb is 97% saturated due to

physiologic shunts

Physiologic shunt

portion of venous blood that travels from the R heart to the L heart without participating in gas exchange

As 2,3 BPG level increases, curve shifts to the ___, decreasing Hb affinity for oxygen

right

The amount of oxygen bound to Hb is directly related to

the partial pressure of oxygen

Hb is highly specialized in structure to

transport O2 and CO2

Hemoglobin saturation with oxygen ___ with changes in PaO2

varies

Relative Shunts responds ____ to oxygen therapy

well


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