NHA Certified Clinical Medical Assistant (CCMA)Clinical Patient CareMedium
A medical assistant is performing a pulse oximetry reading on a patient. The patient has cold hands and is wearing dark nail polish. Which of the following factors is most likely to cause an inaccurate reading?
- APatient's age
- BPatient's height
- CDark nail polish
- DAmbient room temperature
Show answer & explanationAnswer & explanation
Correct answer: C. Dark nail polish
Dark nail polish, especially black or dark blue, can absorb light emitted by the pulse oximeter, leading to falsely low or inaccurate oxygen saturation readings. Cold hands can also affect accuracy by causing vasoconstriction and reduced peripheral perfusion, but dark nail polish is a more direct interferent with the device's light-based measurement.
Why the other options are wrong
- A. Patient's age does not directly cause inaccurate pulse oximetry readings.
- B. Patient's height has no bearing on the accuracy of a pulse oximetry reading.
- D. Ambient room temperature is generally not a direct cause of inaccurate pulse oximetry, although extreme cold can contribute to poor perfusion.
Pulse Oximetry Accuracy Factors
Pulse oximetry measures oxygen saturation. Factors that can interfere with its accuracy include dark nail polish, artificial nails, poor peripheral perfusion (e.g., cold extremities, hypotension), motion artifact, and carbon monoxide poisoning.
- Dark nail polish interferes with light absorption.
- Poor perfusion (cold, hypotension) affects signal.
- Motion artifact causes unreliable readings.
Memory trick: Color on nail, signal will fail.