Upload
donald-raymond
View
276
Download
1
Tags:
Embed Size (px)
DESCRIPTION
Oxygen Transport Lecture notes for Respiratory Therapy Students
Citation preview
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