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VS: Oxygen Saturation

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References:

  1. Kozier & Erb’s Fundamentals of Nursing: Concepts, Process, and Practice, 11th Edition, ISBN 9780135428733, by Audrey Berman, Shirlee J. Snyder, and Geralyn Frandsen (Ch. 28, pp. 532–569)
  2. da Costa, J. C., Faustino, P., Lima, R., Ladeira, I., & Guimarães, M. (2016). Research: Comparison of the Accuracy of a Pocket versus Standard Pulse Oximeter. Biomedical instrumentation & technology, 50(3), 190–193. https://doi.org/10.2345/0899-8205-50.3.190

A pulse oximeter is a noninvasive device that estimates a client’s blood oxygen saturation (SpO₂) by means of a sensor attached to the client’s finger, toe, nose, earlobe, or forehead (or around the hand or foot of a neonate). The oxygen saturation value is the percent of all hemoglobin binding sites that are occupied by oxygen. The pulse oximeter can detect hypoxemia (low oxygen saturation) before clinical signs and symptoms develop.

Normal oxygen saturation is 95% to 100%; below 90% should be evaluated and treated, and below 70% is life-threatening.

The following are some constraints or factors that affect the viability of an oxygen saturation reading.

  1. Hemoglobin: saturation is not related to the amount of red blood cells actually present. A patient with low hemoglobin can still obtain a normal reading of 100% SpO₂ despite compromised oxygen capacity.
  2. Circulation: oximeters rely on circulation to an area to obtain readings. An area with impaired circulation is not a viable site for pulse oximetry. This includes transient causes such as vasoconstriction from cold temperatures or long-standing disease processes such as peripheral vascular diseases.
  3. Activity: shivering or excessive movements of the sensor site may interfere with accurate readings.
  4. Light Interference: sensors often use light as the medium of measurement. Readings may be altered by exposure to light such as sunlight or a bilirubin light.
  5. Carbon monoxide poisoning: pulse oximeters cannot tell the difference between hemoglobin bound with oxygen and hemoglobin bound with carbon monoxide.

Oxygen Saturation Assessment Procedure

Specifications

This procedure is based on the use of pulse oximeters with a separate sensor and a machine. It is common to rely entirely on pocket pulse oximeters that can provide a reading directly. A study (2016) compared pocket vs standard pulse oximeters and found a minimal mean difference (0.01%).

Assessing respirations is done to:

  • Estimate the arterial blood oxygen saturation
  • Detect the presence of hypoxemia before visible signs develop
PhaseNursing Activities
AssessmentAssess the best location for a pulse oximeter based on the client’s age and physical condition. The finger is usually used for adults. Overall condition including risk actors for developing hypoxemia and hemoglobin level should be considered.

Signs of perfusion— vital signs, skin color and temperature, nail bed color, and tissue perfusion of extremities are used a baseline data.

For adhesive-type pulse oximeters, determine whether or not the client may have an allergy to the type of adhesive used.
PlanningAssign: pulse oximetry may be assigned to APs. The nurse interprets the oxygen saturation value and determines appropriate interventions.

Equipment: nail polish remover if needed, pulse oximeter.
ImplementationCheck that the oximeter equipment is functioning normally. Prior to performing the procedure, the nurse must introduce themselves and verify the client’s identity using agency protocol. Explanation of the nurse’s purpose, the procedure, and how the patient will participate.
  1. Perform hand hygiene and observe appropriate infection prevention procedures.
  2. Provide client privacy.
  3. Choose a sensor appropriate for the client’s size and desired location.
    • If the client is allergic to adhesive, use a clip or sensor without adhesive.
    • For oximeters using extremities, ensure that perfusion is adequate.
  4. Prepare the site. It must be clean and dark nail polish must be removed to avoid inaccuracies.
  5. Apply the sensor, and connect it to the pulse oximeter. These may beep, indicating the detecting of arterial pulsations.
  6. Set and turn on the alarm when using continuous monitoring. Presets for high and low oxygen saturation and high and low pulse rates may be set according to agency policy. Audio and visual alarms are double-checked as enabled before leaving the client.
  7. Ensure client safety. Adhesive sensors are inspected (for irritation) and switched sites every 4 hours, and sprint-tension (clip) sensors are inspected and switched sites every 2 hours.
  8. Minimize sources of error:
    • Minimize motion artifacts; use adhesive-type sensors, change sensor site, or immobilize the client if absolutely necessary.
    • Cover the sensor with a sheet or towel to block large amounts of light from external sources, which may interfere with readings.
    • Comparisons of the reported pulse rate and radial pulse should be done periodically.
  9. Document the oxygen saturation on the appropriate record at designated intervals.
EvaluationCompare the oxygen saturation to the client’s previous oxygen saturation level. Relate to pulse rate and other vital signs. Conduct appropriate follow-up such as notifying the primary care provider, adjusting oxygen therapy, or providing breathing treatments.

Pulse Oximetry Across the Lifespan

  1. Infants: an earlobe or forehead sensor may be required if fingers, feet, and toes are not available.
  2. Children: anxiety may be present. Inform the child that the sensor will not hurt. The probe may be disconnected whenever possible to allow for movement of the child.
  3. Older Adults: vasoconstrictive medications, poor circulation, or thickened nails may interfere with readings. A forehead or earlobe sensory may be used if indicated.

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