Pulse oximetry is used to?

Appeared in: AIIMS Bhatinda NO - 2019

Explanation

Pulse oximetry is a noninvasive technique that measures the arterial oxyhemoglobin saturation (SpO₂) of arterial blood.
The reading represents the percentage of hemoglobin molecules that are bound with oxygen.
This measurement directly reflects the amount of oxygen being transported or carried by the blood to the tissues.
A normal SpO₂ range is typically 95% to 100%. A value below 90% is considered a clinical emergency.

Option A: Counting the respiratory rate involves observing the number of breaths a person takes per minute. Pulse oximetry does not measure this; it measures oxygen saturation.
Option B: This refers to ventilation, or the volume of air moving into the lungs. Pulse oximetry measures oxygen in the blood, not the air in the lungs.
Option C: Pulse oximetry measures oxygen, not carbon dioxide. The primary methods for measuring CO₂ are capnography and arterial blood gas (ABG) analysis.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The primary function and clinical application of pulse oximetry as background academic context rather than a clinical decision trigger.
Pulse oximetry is a fundamental vital sign in nursing, used to quickly assess for hypoxia, monitor patients on oxygen therapy, and evaluate respiratory status during and after procedures.
Nurses must be aware of factors that can cause inaccurate SpO₂ readings, such as dark nail polish, poor peripheral circulation, hypothermia, and patient movement.
What if? If a patient has carbon monoxide (CO) poisoning, the pulse oximeter may show a falsely high reading (e.g., 100%). This is because the device cannot differentiate between hemoglobin saturated with oxygen (oxyhemoglobin) and hemoglobin saturated with CO (carboxyhemoglobin). The nurse must rely on other clinical signs of hypoxia.

How to Approach the Question

First, identify the core term in the question, which is 'Pulse oximetry'.
Recall the primary function of this device from your nursing knowledge. Its name gives a clue: 'oxi' refers to oxygen and 'metry' means measurement.
Systematically evaluate each option. Ask yourself, 'Does a pulse oximeter do this?'
Eliminate the option for 'respiratory rate', as that is a separate vital sign (breaths per minute).
Eliminate the option for 'carbon dioxide', as that is measured by capnography or ABG.
Differentiate between 'oxygen taken into the lungs' (ventilation) and 'oxygen carried in the blood' (saturation/perfusion). Pulse oximetry measures the latter.

Concept Tested & Keywords

Concept Tested: The primary function and clinical application of pulse oximetry.
Stem keywords: Pulse oximetry
Lead-in keywords: used to

QkGmbuRxqIs_j5cvfArWSY

E6 Nursing Fundamentals Taylor p. 720-722

E6 Nursing Fundamentals Potter Perry 12e Part 3 pp. 23-25, 24-26

Practise the full AIIMS Bhatinda NO - 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.