During ABG analysis blood is collected from:

OSSSC Nursing Officer-2023

Medical Surgical Nursing

Easy

Appeared in: OSSSC Nursing Officer-2023

Explanation

Arterial blood is the standard sample for ABG analysis because it has just passed through the lungs and accurately reflects the body's overall gas exchange status.
An arterial sample provides direct measurements of arterial oxygen tension (PaO₂), carbon dioxide tension (PaCO₂), and pH, which are essential for evaluating oxygenation and ventilation.
The composition of arterial blood is uniform throughout the systemic circulation, making it a reliable source for assessing a patient's respiratory and metabolic state.

Option B: Venous blood gas levels (VBG) reflect the metabolic activity of the local tissues from which the blood is returning, not the function of the lungs. Oxygen levels are lower and carbon dioxide levels are higher.
Option C: Capillary blood is a mixture of arterial and venous blood, and its values, particularly for PaO₂, do not correlate well with arterial blood. It is less accurate.
Option D: The site is critical. Using venous or capillary blood for an ABG analysis would lead to incorrect interpretation of the patient's respiratory status.

Clinical Relevance

Nursing practice connection: Knowing Arterial Blood Gas (ABG) Sample Collection helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Performing the Allen test before radial artery puncture is a critical patient safety measure to prevent ischemic injury to the hand if the radial artery were to be damaged during the procedure.
After an ABG draw, applying firm pressure for at least 5 minutes is essential to achieve hemostasis and prevent a hematoma, especially since arteries are high-pressure vessels.
What if the patient is on anticoagulant therapy (like heparin or warfarin)? The nurse must apply pressure to the puncture site for a longer duration (e.g., 10-15 minutes) and monitor the site more closely for any signs of bleeding or hematoma.

How to Approach the Question

First, identify the core subject of the question: 'ABG analysis'.
Recall the purpose of an ABG test. Its primary function is to assess lung function, specifically gas exchange (oxygenation and ventilation), and the body's acid-base balance.
Consider the circulatory pathway. Blood flows from the lungs (where it gets oxygenated) into the arteries to be distributed to the body. Blood returns from the body's tissues via the veins.
Deduce that to measure how well the lungs are working, you need a sample of blood immediately after it has left the lungs. This is arterial blood.
Evaluate the options based on this deduction. 'Artery' is the only source of freshly oxygenated blood that reflects lung function. Veins and capillaries contain blood that has already undergone gas exchange at the tissue level, so they are incorrect.

Concept Tested & Keywords

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E6 Pathology-Vandana Puri & Kavita Gaur Textbook of Pathology and Genetics p. 407-409

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 79-81