RN Nursing · Vital Signs · Practice question
A nurse is obtaining an oxygen saturation on a client. Which of the following actions should the nurse take?
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Relocate the sensor every 8 hrs.
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Wait 10 sec after placing the probe before obtaining the oxygen saturation reading.
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✓
Choose a finger with a capillary refill less than 3 seconds.
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Place the sensor probe on the same extremity as an electronic blood pressure cuff.
Answer & explanation
Correct: Choose a finger with a capillary refill less than 3 seconds.
When obtaining a pulse oximetry reading, choosing a finger with capillary refill of less than 3 seconds ensures adequate peripheral perfusion, which is necessary for the sensor to accurately detect pulsatile blood flow and provide a reliable oxygen saturation reading. Poor perfusion — evidenced by capillary refill greater than 3 seconds — can cause falsely low or unobtainable readings because the sensor relies on detecting the difference between oxygenated and deoxygenated hemoglobin in pulsating arterial blood. The sensor should be relocated every 2 hours (not every 8 hours) when continuous monitoring is used to prevent pressure injury and skin breakdown at the sensor site. The nurse should wait at least 10 to 30 seconds after placing the probe — though some sources specify waiting until the waveform stabilizes, not merely 10 seconds — making that option less specifically correct as stated, but the question identifies the perfusion check as most appropriate. Placing the sensor on the same extremity as an electronic blood pressure cuff should be avoided because cuff inflation temporarily occludes blood flow and will interfere with accurate readings during measurement cycles. Selecting a well-perfused digit is the foundational assessment step.
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