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Purposes of the Pulse Oximeter

Pulse oximeters are used by health care workers in medical settings to measure the oxygen saturation of the hemoglobin in blood without a blood sample. Hemoglobin is a protein in the blood that carries oxygen. When oxygen is bound, it is referred to as oxy-hemoglobin; when oxygen is not bound, it is referred to as deoxy-hemoglobin. The pulse oximeter quantifies how much hemoglobin is in the oxy-hemoglobin form.

  1. How to Use a Pulse Oximeter

    • In order to measure oxygen saturation, the device is lightly clamped onto a translucent part of the body, typically the tip of a finger or an earlobe. A pulse oximeter works by emitting light through the translucent body part, and measuring the amount of light absorbed by the blood. The light absorption reveals the amount of oxygen bound to hemoglobin because oxy-hemoglobin absorbs a different amount of light than deoxy-hemoglobin.

    What a Pulse Oximeter Reading Means

    • A normal pulse oximeter reading is between 95 and 100. This number is a percentage, meaning the percentage of hemoglobin that has oxygen bound to it or is in the oxy-hemoglobin form. A reading of below 95 may indicate that the patient is not breathing enough oxygen or may have impaired gas exchange in the lungs. These conditions can lead to decreased oxygen bound to hemoglobin in the blood, thus more deoxy-hemoglobin, less oxy-hemoglobin and a lower oximeter reading.

    When to use a Pulse Oximeter

    • Pulse oximeters may be used to constantly measure the amount of oxygen in a patient's blood in a hospital. They may be used by patients with respiratory or cardiac conditions -- such as emphysema or congestive heart failure -- in order to determine whether their ventilation is adequate to supply body tissues with oxygen. Pilots in unpressurized aircraft may also use pulse oximeters to monitor their oxygen levels when using supplemental oxygen.

    Limitations of Pulse Oximeters

    • Although a person may have a pulse oximeter reading of 100, he may still not have enough oxygen to survive. For example, a high pulse oximeter reading may be obtained from an anemic patient. In anemia, the patient has a decreased number of hemoglobin molecules in the blood. In this case, there is simply not enough hemoglobin to bind sufficient amounts of oxygen to supply body tissues. Additionally, a patient with a high pulse oximeter reading may also have high levels of carbon dioxide, which is not measured by a pulse oximeter. High levels of carbon dioxide in the blood can be fatal.

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