Pulse Oximetry

  • Used to noninvasively monitor arterial oxygen saturation.
  • A photo detector slipped over the finger measures transmitted light as it passes through the vascular bed, detects the relative amount of color absorbed by arterial blood, and calculates exact mixed venous oxygen saturation without interference from surrounding venous blood, skin, connective tissue, or bone.


  • Oximeter
  • Sensor probe
  • Alcohol pads
  • Nail polish remover, if necessary

Preparation of Equipment

  • Review the manufacturer’s instruction for assembly.


  • Reinforce the explanation of the procedure to the patient.

Using a finger probe

  • Select a finger (usually index finger) on the patient’s nondominant hand, if possible for placement of the probe.
  • Remove fake fingernail and nail polish from the test finger.
  • Place the transducer (photoprotector) probe over the patient’s finger so the light beams and sensor oppose each other.
  • Trim long fingernails or position the probe perpendicular to the finger.
  • Position the patient’s hand at heart level.
  • Turn on the power switch. If the device is working properly, a beep will sound, a display will light momentarily, and the pulse search light will flash.
  • After four to six heartbeats the pulse amplitude indicator will begin tracking the pulse.
  • Rotate the sensor site according to the manufacturer’s instructions.
  • Clean the probe per facility policy between patients or, if disposable, discard.

Nursing Interventions

  1. Some machines have a pleth wave. A steady, level, even wave form ensures that the numerical reading is accurate.
  2. The pulse rate on the oximeter should correspond to the patient’s actual pulse. If it doesn’t, monitor the patient, check the oximeter, and reposition the probe.
  3. Factors that interfere with accuracy include:
    • Elevated carboxyhemoglobin or methemoglobin levels
    • Lipid emulsions and dyes
    • Excessive light
    • Excessive patient movement
    • Hypothermia
    • Hypotension
    • Vasoconstriction
    • Medications such as dapsone, vasopressors.
  4. Use the bridge of the nose if the patient has compromised circulation in his extremities.
  5. If an automatic blood pressure cuff is used on the same extremity as the saturation probe is placed, the cuff will interfere with oxygen saturation readings during inflation.
  6. If the light is a problem, cover the probes.
  7. If patient movement is the problem, move the probe or select a different probe.
  8. Notify the physician of any significant change in the patient’s condition.

Daisy Jane Antipuesto RN MN

Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.

What Do You Think?