ESR is considered to be the measure of following blood physical-chemical property.

OSSSC Nursing Officer-2023

Applied Physiology

Easy

Appeared in: OSSSC Nursing Officer-2023

Explanation

ESR measures the rate at which red blood cells (erythrocytes) settle in a tube of anticoagulated blood, which is a direct measure of the blood's suspensial properties.
The stability of blood as a suspension depends on the balance between factors causing RBCs to settle (gravity) and factors keeping them suspended (repulsive surface charges).
In inflammatory states, increased plasma proteins like fibrinogen cause RBCs to form rouleaux (stacks), which are heavier and settle faster.
A faster settling rate (higher ESR) signifies decreased suspension stability, making 'blood suspensial properties' the correct answer.

Option A: While plasma contains colloids, ESR specifically measures the sedimentation of cellular components (RBCs) which are in suspension, not the stability of the plasma colloids themselves. This option is less precise.
Option C: The volume of the blood's cellular part, primarily RBCs, is measured by the Packed Cell Volume (PCV) or hematocrit, not the ESR.
Option D: Blood velocity refers to the speed of blood flow through the circulatory system. It is a hemodynamic parameter and is unrelated to the in-vitro ESR test.

Clinical Relevance

Nursing practice connection: Knowing Physical-chemical properties of blood measured by Erythrocyte Sedimentation Rate (ESR) helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
ESR is a widely used, non-specific screening test that indicates the presence of inflammation, infection, autoimmune disease, or malignancy.
While not diagnostic for any single condition, it is valuable for monitoring disease activity and response to treatment in chronic inflammatory disorders like rheumatoid arthritis and tuberculosis.
What if? If a patient has sickle cell anemia, the ESR will be paradoxically low even during an inflammatory crisis. This is because the abnormal 'sickle' shape of the RBCs prevents them from forming rouleaux, thus slowing their sedimentation rate.

How to Approach the Question

First, identify the core concept of the question, which is the principle behind the Erythrocyte Sedimentation Rate (ESR).
Recall the definition of ESR: it is the rate at which red blood cells settle or sediment out of plasma.
Analyze the nature of blood: it is a suspension of cells (like RBCs) in a liquid medium (plasma).
Evaluate the options based on this understanding. The act of settling is a characteristic property of a suspension. Therefore, 'Blood suspensial properties' is the most accurate description.
Eliminate the other options by defining them. 'Volume of blood cellular part' is hematocrit/PCV. 'Blood velocity' is the speed of blood flow. 'Stability of colloid solution' is related but less specific than 'suspensial properties' for a test measuring cell sedimentation.

Concept Tested & Keywords

Concept Tested: Physical-chemical properties of blood measured by Erythrocyte Sedimentation Rate (ESR)
Stem keywords: ESR, measure, blood, physical-chemical property
Lead-in keywords: BEST, MOST RELEVANT CLUE
Negative lead-in flag: false

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E6 Physiology Essentials Sembulingam 10e Part 1 pp. 97-99, 99-101

E6 Physiology Guyton 4SAE Part 1 p. 172-174