Pulse oximeter is a non invasive method to assess the level of

KGMU 2024

Medical & Surgical Nursing

Easy

Appeared in: KGMU 2024

Explanation

A pulse oximeter is a non-invasive device that measures the peripheral oxygen saturation of arterial blood (SpO₂).
SpO₂ is a reliable estimate of arterial oxygenation, which represents the percentage of hemoglobin molecules in arterial blood that are saturated with oxygen.
The device functions by emitting red and infrared light through a pulsating arterial bed (e.g., a fingertip) and measuring the differential absorption of light by oxygenated and deoxygenated hemoglobin.
A normal SpO₂ reading is typically 95% or higher in a healthy individual.

Option B: The Fraction of Inspired O₂ (FiO₂) is the concentration of oxygen in the air a patient breathes. It is a therapeutic setting on an oxygen delivery device, not a physiological measurement taken from the patient.
Option C: O₂ intake, or oxygen consumption (VO₂), is the amount of oxygen used by the body's tissues. This is a complex metabolic measurement and is not assessed by pulse oximetry.
Option D: Stroke volume is the volume of blood pumped from the heart's left ventricle with each contraction. It is a measure of cardiac function, not respiratory oxygenation.

Visual 1: Diagram: How a pulse oximeter works, showing the light emitter and photodetector on a fingertip, illustrating how light passes through tissue to measure oxygenated and deoxygenated hemoglobin.
Visual 2: Chart: SpO₂ levels and their clinical interpretation, with color-coded zones for Normal (95-100%), Mild Hypoxemia (91-94%), and Severe Hypoxemia (below 90%).
Visual 3: Infographic: Common sites for pulse oximeter probe placement, including the finger, toe, earlobe, and forehead, with notes on when to use alternative sites.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Function and measurement principle of a pulse oximeter as background academic context rather than a clinical decision trigger.
Nurses rely on pulse oximetry for rapid, continuous, and non-invasive monitoring of a patient's respiratory status, making it a standard part of vital sign assessment in nearly all clinical settings.
An SpO₂ reading below 90% is considered a clinical emergency. A nurse's first action is to assess the patient's airway and breathing, ensure the probe is correctly placed, and prepare to administer oxygen and notify the physician.
What if? If a patient is rescued from a house fire and has an SpO₂ of 99%, the nurse should not be falsely reassured. In carbon monoxide poisoning, the pulse oximeter gives a falsely high reading because it cannot differentiate between hemoglobin bound to oxygen and hemoglobin bound to carbon monoxide. An arterial blood gas (ABG) is essential for an accurate assessment.

How to Approach the Question

First, identify the core subject of the question: the function of a 'pulse oximeter'.
Recall the primary purpose of this common clinical device. It is used to check 'sats' or oxygen levels in the blood.
Analyze the options based on this primary function. 'Arterial oxygenation' directly relates to the measurement of oxygen in the blood.
Systematically eliminate the other options. 'Fraction of inspired O2' is what is delivered to the patient. 'O2 intake' is a metabolic measure. 'Stroke volume' is a cardiac measure.
Confirm that the pulse oximeter's measurement of SpO₂ is a direct, non-invasive assessment of arterial oxygenation, making it the correct choice.

Concept Tested & Keywords

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