pulse ox

pulse ox

1. Pulse oximeter, see there.
2. Pulse oximetry, see there.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

pulse ox

A colloquial term for a pulse oximeter.
Medical Dictionary, © 2009 Farlex and Partners

Pulse Oximetry

Synonym/acronym: Oximetry, pulse ox.

Common use

To assess arterial blood oxygenation toward evaluating respiratory status during ventilation, acute illness, activity, and sleep and to evaluate the effectiveness of therapeutic interventions.

Area of application

Earlobe, fingertip; for infants, use the large toe, top or bottom of the foot, or sides of the ankle.




Pulse oximetry is a noninvasive study that provides continuous readings of arterial blood oxygen saturation (SpO2) using a sensor site (earlobe or fingertip). The SpO2 equals the ratio of the amount of O2 contained in the hemoglobin to the maximum amount of O2 contained, with hemoglobin expressed as a percentage. The results obtained may compare favorably with O2 saturation levels obtained by arterial blood gas analysis without the need to perform successive arterial punctures. The device used is a clip or probe that produces a light beam with two different wavelengths on one side. A sensor on the opposite side measures the absorption of each of the wavelengths of light to determine the O2 saturation reading. The displayed result is a ratio, expressed as a percentage, between the actual O2 content of the hemoglobin and the potential maximum O2-carrying capacity of the hemoglobin.

This procedure is contraindicated for



  • Determine the effectiveness of pulmonary gas exchange function
  • Evaluate suspected nocturnal hypoxemia in chronic obstructive pulmonary disease
  • Monitor oxygenation during testing for sleep apnea
  • Monitor oxygenation perioperatively and during acute illnesses
  • Monitor oxygenation status in patients on a ventilator, during surgery, and during bronchoscopy
  • Monitor O2 saturation during activities such as pulmonary exercise stress testing or pulmonary rehabilitation exercises to determine optimal tolerance
  • Monitor response to pulmonary drug regimens, especially flow and O2 content

Potential diagnosis

Normal findings

  • Greater than or equal to 95%

Abnormal findings related to

  • Abnormal gas exchange
  • Hypoxemia with levels less than 95%
  • Impaired cardiopulmonary function

Critical findings


Interfering factors

  • Patients who smoke or have suffered carbon monoxide inhalation, because O2 levels may be falsely elevated.
  • >Factors that may result in incorrect values

    • Patients with anemic conditions reflecting a reduction in hemoglobin, the O2-carrying component in the blood.
    • Excessive light surrounding the patient, such as from surgical lights.
    • Impaired cardiopulmonary function.
    • Lipid emulsion therapy and presence of certain dyes.
    • Movement of the finger or ear or improper placement of probe or clip.
    • Nail polish, artificial fingernails, and skin pigmentation when a finger probe is used.
    • Vasoconstriction from cool skin temperature, drugs, hypotension, or vessel obstruction causing a decrease in blood flow.
  • Other considerations

    • Accuracy for most units is plus or minus 4% with a standard deviation of 1%.

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this procedure can assist in monitoring oxygen in the blood.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s cardiovascular and respiratory systems, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Address concerns about pain related to the procedure and explain that no pain is associated with the procedure. Inform the patient that the procedure is generally performed at the bedside, in the operating room during a surgical procedure, or in the office of a health-care provider (HCP). Explain that the procedure lasts as long as the monitoring is needed and could be continuous.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • If a finger probe is used, instruct the patient to remove artificial fingernails and nail polish.
  • When used in the presence of flammable gases, the equipment must be approved for that specific use.
  • Instruct the patient not to smoke for 24 hr before the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient.
  • Ensure that the patient has complied with pretesting instructions.
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • If a finger probe is used, instruct the patient not to grip treadmill rail or bed rail tightly; doing so restricts blood flow.
  • Instruct the patient to cooperate fully and to follow directions.
  • Massage or apply a warm towel to the upper earlobe or finger to increase the blood flow.
  • The index finger is normally used, but if the patient’s finger is too large for the probe, a smaller finger can be used.
  • If the earlobe is used, make sure good contact is achieved.
  • The big toe, top or bottom of the foot, or sides of the heel may be used in infants.
  • Place the photodetector probe over the finger in such a way that the light beams and sensors are opposite each other. Turn the power switch to the oximeter monitor, which will display information about heart rate and peripheral capillary saturation (SaO2).
  • Remove the clip used for monitoring when the procedure is complete.


  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Closely observe SpO2, and report to the HCP if it decreases to 90%.
  • Recognize anxiety related to test results, and be supportive of perceived loss of independent function. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include α1-AT, anion gap, arterial/alveolar oxygen ratio, biopsy lung, blood gases, bronchoscopy, carboxyhemoglobin, chest x-ray, chloride sweat, CBC, CBC hemoglobin, CBC WBC count and differential, CT angiography, culture and smear for mycobacteria, culture bacterial sputum, culture viral, cytology sputum, ECG, Gram stain, IgE, lactic acid, lung perfusion scan, lung ventilation scan, MR angiography, MR chest, osmolality, phosphorus, plethysmography, pleural fluid analysis, potassium, pulmonary function tests, sodium, and TB skin test.
  • Refer to the Cardiovascular and Respiratory systems tables at the end of the book for related tests by body system.
Handbook of Laboratory and Diagnostic Tests, © 2013 Farlex and Partners
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