Cardiopath: Oxygenation Assessment Flashcards

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Questions and Answers

What two ways is oxygen transported in the blood?

Dissolved oxygen in blood plasma, and bound to the hemoglobin

At normal body temperature, how much O2 will dissolve in each 100 mL of blood for every 1 mm Hg of PO2?

0.003 mL

What is the normal hemoglobin value in men?

14 to 16 g/dL

What is the normal hemoglobin value in women?

12 to 15 g/dL Signup and view all the answers

What is the normal hemoglobin value in infants?

14 to 20 g/dL Signup and view all the answers

Each g% of Hb is capable of carrying approximately how much O2?

1.34 mL O2 Signup and view all the answers

What is oxygen bound to hemoglobin expressed as?

16.08 volume % O2 Signup and view all the answers

What are the two normal physiologic shunts?

Thesbian venous drainage into the left atrium; Bronchial venous drainage into the pulmonary veins Signup and view all the answers

The total oxygen content can be calculated in which types of blood?

Arterial blood, Venous blood, Pulmonary capillary blood Signup and view all the answers

What does the oxygen dissociation curve illustrate?

The S-shaped curve that shows the percentage of hemoglobin connected to oxygen at a specific oxygen pressure. Signup and view all the answers

What are the two categories of oxygen transport studies?

Oxygen tension-based indices; Oxygen saturation and content-based indices Signup and view all the answers

What is the arterial oxygen tension (PaO2)?

Good indicator of the patient's oxygenation status Signup and view all the answers

What is the normal range for P(A-a) O2 on room air at sea level?

7-15 mmHg, should not exceed 30 Signup and view all the answers

What is the normal range for the arterial alveolar pressure ratio (PaO2/PAO2)?

0.75-0.95 Signup and view all the answers

What is the amount of oxygen delivered to peripheral tissue cells normally?

About 1000 mL of oxygen/minute Signup and view all the answers

The difference between the CaO2 and the CvO2 is normally about how much?

5 mL Signup and view all the answers

What is hypoxemia?

An abnormally low PaO2 Signup and view all the answers

What is hypoxia?

An inadequate level of tissue oxygenation Signup and view all the answers

What is cor pulmonale?

Pulmonary arterial hypertension, Right hypertrophy, Increased right ventricular work, Right ventricular failure Signup and view all the answers

What are the three major causes of cor pulmonale?

Increased viscosity of blood; Increased vascular resistance due to hypoxic vasoconstriction; Obliteration of the pulmonary capillary bed Signup and view all the answers

Study Notes

Oxygen Transport in Blood

Oxygen is transported in blood either dissolved in plasma or bound to hemoglobin.
At normal body temperature, each 100 mL of blood dissolves 0.003 mL of O2 for every 1 mm Hg of PO2, clinically noted as 0.3 mL/dL.

Hemoglobin Values

Normal hemoglobin values:
- Men: 14 to 16 g/dL
- Women: 12 to 15 g/dL
- Infants: 14 to 20 g/dL
Each gram of hemoglobin can carry approximately 1.34 mL of O2.

Oxygen Content and Indices

Total oxygen content is calculated in arterial, venous, and pulmonary capillary blood.
Oxygenation indices can be categorized into oxygen tension-based and saturation-content-based indices.

Arterial Oxygen Tension (PaO2)

PaO2 is a reliable indicator of oxygenation status but may be misleading in cases of low hemoglobin, decreased cardiac output, peripheral shunting, or carbon monoxide exposure.
Alveolar-arterial oxygen tension difference (P(A-a)O2) typically ranges from 7-15 mm Hg on room air and should not exceed 30 mm Hg.

Conditions Affecting Oxygen Values

P(A-a)O2 increases with oxygen diffusion disorders, V/Q mismatching, right-to-left shunting, and aging.
The arterial-alveolar oxygen pressure ratio (PaO2/PAO2) indicates the flow of alveolar oxygen into the arterial blood, with a normal range of 0.75-0.95.

Indicators of Pulmonary Function

Decreased PaO2/PAO2 ratios signal lung abnormalities, with significant values indicating pulmonary shunting, diffusion defects, and ventilation-perfusion mismatching.
The PaO2/FiO2 ratio helps assess lung diffusion defects, with a room air range of 350-450; values below 200 suggest poor lung function.

Oxygen Content Calculations

CaO2 reflects total arterial oxygen content, while CvO2 (mixed venous blood) incorporates hemoglobin, oxygen saturation, and dissolved oxygen.
CcO2 (pulmonary capillary blood) is calculated similarly but focuses on alveolar conditions.

Oxygen Delivery and Consumption

The average oxygen delivery rate to peripheral tissues is about 1000 mL/min, measured by cardiac output.
The difference between CaO2 and CvO2 typically measures around 5 mL, useful in assessing cardiopulmonary status.

Factors Influencing Oxygen Dynamics

Factors increasing C(a-v)O2 difference include decreased cardiac output, exercise, seizures, and hyperthermia.
Factors decreasing the difference include increased cardiac output, muscle relaxation, and hypothermia.
Oxygen consumption ranges around 250 mL/min and can rise with factors like seizures and exercise.

Understanding Oxygen Extraction Ratio (O2ER)

O2ER represents consumed oxygen divided by delivered oxygen, with a normal amount of 25%.
Factors enhancing O2ER involve decreased cardiac output or increased oxygen consumption.

Blood Oxygen Saturation Levels

Mixed SvO2 serves as an early indicator of changes in the patient’s oxygen status, normally about 75%.
Factors increasing SvO2 include improved respiratory function and increased cardiac output, while changes that decrease it involve exercise and respiratory disease.

Clinical Relevance of Oxygenation Knowledge

Understanding the degree of pulmonary shunting aids in developing effective patient care plans.
Key parameters for assessing pulmonary shunting include barometric pressure, oxygen tensions, and hemoglobin concentration.

Hypoxemia and Hypoxia

Hypoxemia refers to low PaO2 levels, while hypoxia indicates inadequate tissue oxygenation, which can be classified into hypoxic, anemic, circulatory, or histotoxic types.

Cor Pulmonale

Defined as pulmonary arterial hypertension leading to right ventricular hypertrophy and potential failure.
Major causes include increased blood viscosity, increased vascular resistance due to hypoxia, and capillary bed obliteration.

Hypoxic Vasoconstriction

This phenomenon arises in response to decreased alveolar oxygen (PaO2) in chronic respiratory disorders, facilitating adaptation to hypoxic conditions.

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Description

Test your knowledge on the assessment of oxygenation in the cardiovascular system with these flashcards. Learn about how oxygen is transported in the blood, the normal hemoglobin values, and related clinical details. Perfect for students in medicine or healthcare fields.