OXYGEN TRANSPORT

LEARNING OBJECTIVES

Competency

Examine the Oxygen transport system

Learning Objectives:

Explain the mechanism that Oxygen is

transported in the blood

Utilize the Oxygen disassociation curve

Explain the significance of the curve shifts

Calculate Oxygen transport values

TWO TYPES OF OXYGEN

TRANSPORT

Oxygen is carried in the blood in two ways.

As dissolved oxygen in the blood plasma. Chemically bound to the hemoglobin

Oxygen carrying capacity

Hemoglobin Values

OXYGEN DISSOCIATION

CURVE

Student to Draw Curve through lecture

Distribute graph paper

50% Saturation of Hemoglobin with Oxygen

(P50)

Another important reference point on the

oxygen dissociation curve is the P50 figure.

This value represents the partial pressure at

which the hemoglobin is 50% saturated with

oxygen.

Factors that Shift the Curve

pH: As pH decreases, the curve shifts to the

right, enhancing the unloading of oxygen at

the cells in the tissues.

Dr. John Walsh would say “Acidosis is the

body’s friend”

Factors that Shift the Curve

Factors that Shift the Curve to the

Left

< Temp

>pH

<PCO2

< 2,3 DPG

Curve shifts

Fetal hemoglobin:

Hemoglobin in infants less than 1 year old is

chemically different from adult hemoglobin..

Carbon monoxide hemoglobin

Carbon monoxide has a tremendous ability to

bond with __________; thus, a small amount

of CO can "tie up" a large amount of

____________ and prevent ______ from

bonding with _______.

.Summary view of shift of the Curve

Oxygen Dissociation Curve Shifts

and Abnormal Pressure

If a person’s partial pressure of oxygen is normal (80

to 100 mm Hg), then shifts in the curve are not

clinically significant.

However @#$@#$@$#@#

Please in Groups answer the following

questions

Explain the Benefit of the Right shift clinically

Explain the Benfit of the Left shift clinically

Explain the Bohr effect

Where does the shift occur in the Bohr effect?

Label where 1-6 are

measured. List 7-11

1. O2 Extraction

ratio

2. O2

Consumption

3. O2 delivery

4. SVO2 & PVO2

obtained

5. PaO2 & SaO2

obtained

6. AVO2

difference

where

obtained

• PaO2____

• SaO2_____

• SvO2____

• PvO2____

• Hgb____

OXYGEN TRANSPORT STUDIES

•Total Oxygen DeliveryThe total oxygen delivery value is calculated as the total cardiac output times the oxygen content of arterial blood multiplied by a factor of 10.

Oxygen Transport

• Hemodynamic calculations

Total oxygen delivery

• Decreases when there is a decrease in

–Blood oxygenation

–Hemoglobin concentration

–Cardiac output

Arterial-Venous Oxygen Content Difference

• The arterial-venous oxygen content difference is the total oxygen content of arterial blood minus the oxygen content of mixed venous blood.

Factors that increase the arterial-venous oxygen content difference

include:

• Decreased cardiac output

• Periods of increased oxygen consumption, such as exercise, seizures, shivering, and hyperthermia

Factors that decrease the arterial-venous oxygen content difference

include:

• Increased cardiac output

• Skeletal muscle relaxation

• Peripheral shunting, such as that associated with systemic infection or trauma

• Poisons that prevent cellular metabolism- cyanide poisoning

• Hypothermia

Oxygen Consumption

• Also called oxygen uptake, oxygen consumption is the amount of oxygen extracted by the peripheral tissues in 1 minute.

Factors that increase oxygen consumption include:

• Exercise

• Seizures

• Shivering

• Hyperthermia

• Other activities that increase the metabolic rate

Oxygen Extraction Ratio

• Oxygen Extraction RatioThe oxygen extraction ratio is the amount of oxygen extracted by the peripheral tissues divided by the amount of oxygen delivered to the peripheral cells.

Oxygen Extraction Ratio

• Under normal circumstances, the oxygen extraction ratio is about 25%.

• This means that the hemoglobin molecules that return to the alveoli are about 75% saturated with oxygen.

Factors that increase the oxygen extraction ratio :

• Situations where there is greater demand for Oxygen to the tissues

• Decreased cardiac output

Factors that increase the oxygen extraction ratio :

• Exercise

• Seizures

• Shivering

• Burns

• Trauma

• Anemia

• Decreased arterial oxygenation

Factors that decrease the oxygen extraction ratio

• ___________

• ___________

• ___________

• ___________

• ___________

Mixed Venous Oxygen Saturation

• Normal mixed venous oxygen saturation is about 75%

SVO2

• A low mixed venous oxygen saturation level means the extraction of oxygen from the blood at the tissue level is excessive.

Factors that decrease mixed venous oxygen saturation include:

• Decreased cardiac output

• Periods of increased oxygen consumption, such as exercise, seizures, shivering, hyperthermia, and recovery from burn injuries or significant trauma

So!!!!!!!!!!!!!!!

• If the SvO2 is low it is an indication that the tissue extraction is_______________

Pulmonary Shunting

• Shunt can be very simply defined as perfusion without ventilation.

• How many types of pulmonary shunts are there?

True shunting

• Anatomic shunt blood R to L without gas exchange

• Normal anatomic shunted blood comes from three veins: –Bronchial,

–Pleural

–Thebesian ( sounds like the aliens in Galaxy Quest! )

Capillary shunt

• The sum of anatomic and capillary shunts is called the true, or absolute, shunt.

• Examples of this would be:

–Atelctasis

–Pneumonia

–Pulmonary Edema

Absolute shunt

• Can Oxygen delivery treat a patient with a high shunt fraction?

Pathologies causing a shunt like effect

• Hypoventilation

• Uneven distribution of ventilation, such as that due to bronchospasm or excessive mucus in the tracheobronchial tree

• Alveolar-capillary diffusion defects

• Can we treat this with Oxygen?

Venous Admixture and Arterial Blood Gases

• This blood mixture is what is measured in arterial blood gases

Shunt Equation

• The shunt equation allows the respiratory care practitioner to calculate the degree of shunting that is present.

Clinical Significance of Shunting

• 10% to 20%: intrapulmonary abnormality is present

• 20% to 30%: significant intrapulmonary abnormality

• 30% or greater aggressive suppport required.

CONDITIONS THAT AFFECT THE AMOUNT OF OXYGEN AVAILABLE

TO TISSUES

• Hypoxic hypoxia

• Anemic hypoxia

• Circulatory hypoxia

• Histotoxic hypoxia

Other circulatory concerns

• Cyanosis

• Polycythemia