- Provides an estimate of arterial oxyhemoglobin saturation by using selected wavelengths of light to noninvasively determine the saturation of oxyhemoglobin. Oximeters function by passing a light beam through a vascular bed, such as the finger or earlobe, to determine the amount of light absorbed by oxygenated (red) and deoxygenated (blue) blood.
- Calculates the amount of arterial blood that is saturated with oxygen (Sao2) and displays this as a digital value.
- Indications include:
- Monitor adequacy of oxygen saturation; quantify response to therapy.
- Monitor unstable patient who may experience sudden changes in blood oxygen level.
- Evaluation of need for home oxygen therapy.
- Determine supplemental oxygen needs at rest, with exercise, and during sleep.
- Need to follow the trend and need to decrease number of ABG sample drawn.
- The oxyhemoglobin dissociation curve allows for correlation between Sao2 and PaO2
- Increased body temperature, acidosis, and increased 2,3- DPG cause a shift in the curve to the right, thus increasing the ability of hemoglobin to release oxygen to the tissues.
- Decreased temperature, decreased 2,3-DPG, and alkalosis cause a shift to the left, causing hemoglobin to hold on to the oxygen, reducing the amount of oxygen being released to the tissues.
- Increased bilirubin, increased carboxyhemoglobin, low perfusion or Sao2 < 80% may alter light absorption and interfere with results
NURSING ALERT
There is a potential error in Sao2 readings of ±2% that can increase to greater than 2% if the patient's SpO2 drops below 80%. Oximeters rely on differences in light absorption to determine Sao2. At lower saturations, oxygenated hemoglobin appears bluer in color and is less easily distinguished from deoxygenated hemoglobin. ABG analysis should be used in this situation.
Nursing and Patient Care Considerations
- Assess patient's hemoglobin. Sao2 may not correlate well with PaO2 if hemoglobin is not within normal limits.
- Remove patient's nail polish because it can affect the ability of the sensor to correctly determine oxygen saturation, particularly polish with blue or dark colors.
- Correlate oximetry with ABG values and then use for single reading or trending of oxygenation (does not monitor Paco2).
- Display heart rate should correlate with patient's heart rate.
- To improve quality of signal, hold finger dependent and motionless (motion may alter results) and cover finger sensor to occlude ambient light.
- Assess site of oximetry monitoring for perfusion on a regular basis, because pressure ulcer may occur from prolonged application of probe.
- Device limitations include motion artifact, abnormal hemoglobins (carboxyhemoglobin and methemoglobin), I.V. dye, exposure of probe to ambient light, low perfusion states, skin pigmentation, nail polish or nail coverings, and nail deformities such as severe clubbing.
- Document inspired oxygen or supplemental oxygen and type of oxygen delivery device.
- Accuracy can be affected by ambient light, I.V. dyes, nail polish, deeply pigmented skin, patients in sickle cell crisis, jaundice, severe anemia, and use of antibiotics such as sulfas.
