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Feb.25.2021

Pulse Oximetry (Neonatal) - CE

ALERT

To decrease morbidity and mortality, the generally accepted range for peripheral oxygen saturation (SpO2) in a neonate is 88% to 92%.undefined#ref5">5

Place the pulse oximeter probe on the right extremity to provide a preductal reading in the delivery room.

OVERVIEW

The goal of oxygen therapy is to deliver sufficient oxygen to the tissues while avoiding hyperoxia and oxygen toxicity. Preterm neonates are especially vulnerable to the effects of hypoxia and hyperoxia.2 Toxic oxygen radicals increase in hyperoxia and in reoxygenation after hypoxemia, resulting in oxidative stress. Oxidative stress is a result of the preterm neonate’s deficiency in the quantity and function of antioxidants that protect the cells from free radicals. Oxidative stress is associated with the development of bronchopulmonary dysplasia and retinopathy of prematurity (ROP).1 Because premature neonates experience intermittent periods of hypoxia and hyperoxia, monitoring the saturations of hemoglobin saturated with oxygen in these patients’ blood is critical.

Pulse oximetry is the most common method of determining arterial oxygen saturation. Circumferential tape probes are wrapped around the neonate’s hand, wrist, foot, or ankle. This pulse oximeter probe contains a light source, a light detector, and a microprocessor, which calculates the differences in the oxygen-rich versus oxygen-poor hemoglobin. Pulse oximetry uses red and infrared light to determine the saturation of hemoglobin bound to oxygen. The oxygen-rich hemoglobin absorbs more of the infrared light, and the hemoglobin without oxygen absorbs more of the red light (Figure 1)Figure 1. The microprocessor calculates the difference between the two and displays a percentage on the monitor. SpO2 is the percentage of the available hemoglobin that carries oxygen.3,5

The generally accepted range for SpO2 in neonates is 88% to 92%.5 Recommendations for accepting SpO2 between 85% and 95% are also seen in current literature; however, some studies in extremely low-birth-weight neonates have demonstrated that targeting saturation levels less than 90% is associated with lower partial pressure of arterial oxygen (PaO2) levels and higher morbidity.7 The goal is to avoid large variations in saturation levels that have the potential to lead to lung injury and ROP.5 Keeping the SpO2 level between 90% and 92%3 to keep the neonate in a normoxic state is ideal. In general, oxygen is given for saturations less than 85% and weaned for saturations greater than 95%.4

A neonate’s SpO2 depends on three parameters: the amount and type of hemoglobin present, how well it moves throughout the body, and how easily oxygen binds to and releases from hemoglobin to enter the cells.5

Amount and Type of Hemoglobin Present

The neonate is unique in that fetal hemoglobin accounts for approximately 80% of the term neonate’s blood volume at birth.7 In utero, the total amount of fetal hemoglobin is gradually replaced with adult hemoglobin starting at 32 weeks’ gestation.7 This gradual replacement continues after birth unless blood transfusions and exchange transfusions hasten the process. Fetal hemoglobin has an increased affinity for oxygen that results in a pulse oximeter SpO2 reading higher for a given PaO2 than if fetal hemoglobin were not present. SpO2 values between 85% and 93% may have a PaO2 level between 40 and 80 mm Hg.1

Neonates with decreased hemoglobin concentrations (from anemia or hemorrhage) may have normal SpO2 and still be hypoxemic. Even though the hemoglobin present may be fully saturated, the neonate does not have sufficient hemoglobin to carry enough oxygen to meet the body’s needs.

How Well Hemoglobin Moves Throughout the Body

Neonates with decreased perfusion, from shock, bradycardia, or congenital heart disease, may start with normal SpO2, but because of a decreased blood flow, the hemoglobin is in prolonged contact with cells. The cell’s oxygen demands are increased, the hemoglobin releases oxygen easily, but the blood takes longer to return to the lungs for reoxygenation.

How Easily Oxygen Binds to and Releases from Hemoglobin and Enters the Cells

The amount of oxygen bound to the hemoglobin is dependent on the PaO2 to which the hemoglobin is exposed. In the lungs, at the alveolar–capillary interface, the PaO2 is high, and therefore the oxygen binds readily to the hemoglobin. As the blood circulates to other body tissues in which the PaO2 level is lower, the hemoglobin releases the oxygen into the tissue. Specifically, the binding of oxygen to hemoglobin varies with the PaO2. The relationship is nonlinear and forms an S-shaped curve called the oxyhemoglobin dissociation curve (ODC). In its simplest form, this curve describes the relation between the PaO2 (x-axis) and the SpO2 (y-axis) (Figure 2)Figure 2. Factors that determine the position of the ODC include temperature, arterial partial pressure of carbon dioxide (PaCO2), and pH.5

Right shift—Lower oxygen affinity:

A shift to the right in the ODC means the hemoglobin’s affinity for oxygen has decreased and the hemoglobin readily releases oxygen at the cellular level. Factors that move the ODC to the right include physiologic states where tissues need more oxygen, including:5

  • Increased PaCO2
  • Decreased pH
  • Increased temperature

Left shift—Higher oxygen affinity:

A shift to the left in the ODC means the hemoglobin’s affinity for oxygen has increased and the hemoglobin is released less readily at the cellular level. Factors that move the ODC to the left include:5

  • Increased fetal hemoglobin
  • Increased pH
  • Decreased temperature
  • Decreased PaCO2

Pulse oximetry readings are altered or not obtainable because of certain conditions:3

  • Incorrect placement of the sensor
  • Movement, causing artifact
  • Phototherapy
  • Low perfusion states
  • Dark skin pigmentation
  • Presence of ink or dyes (e.g., footprint ink)
  • Severe hyperbilirubinemia
  • Severe anemia

Current models of pulse oximeters reduce the artifact that results from motion and low perfusion.3

Monitoring of a neonate’s SpO2 levels begins at birth in the delivery room. At delivery, the neonate has not transitioned completely away from a fetal circulation pattern with the potential for shunting of blood. Placing the pulse oximeter probe only on the right upper extremity provides a preductal saturation. The preductal saturation accurately reflects the patient’s true status during transition.6 For a neonate at 1 minute old, the SpO2 goal is 60% to 64%, increasing gradually to 85% to 95% by 10 minutes old (Table 1)Table 1.2

EDUCATION

  • Provide developmentally and culturally appropriate education based on the desire for knowledge, readiness to learn, and overall neurologic and psychosocial state.
  • Explain the patient’s underlying condition, the reasons for pulse oximetry monitoring, and the meaning of the SpO2 reading.
  • Review with the family the pulse oximeter alarm and explain the causes of false alarms, including movement.
  • Encourage questions and answer them as they arise.

ASSESSMENT AND PREPARATION

Assessment

  1. Perform hand hygiene before patient contact.
  2. Introduce yourself to the family.
  3. Verify the correct patient using two identifiers.
  4. Assess the family’s understanding of the reasons for and the risks and benefits of the procedure.
  5. Assess any pertinent medical history or current condition that predisposes the patient to alterations in oxygenation, ventilation, and acid-base balance including serum hemoglobin level.
  6. Assess the patient’s respiratory status, including respiratory rate, work of breathing, and breath sounds.
  7. Assess for signs of inadequate oxygenation and ventilation.
  8. Assess for conditions (e.g., anemia, hyperbilirubinemia) that prevent accurate monitoring of SpO2 with a pulse oximeter.
  9. Assess the intended site of probe placement for adequacy of perfusion or altered skin integrity.
  10. Assess the patient’s current gestational age to assist in determining the appropriate SpO2 range.

PROCEDURE

  1. Perform hand hygiene.
  2. Verify the correct patient using two identifiers.
  3. Explain the procedure to the family and ensure that they agree to treatment.
  4. Select an appropriate pulse oximeter site.
    Rationale: Site selection may affect the accuracy of pulse oximeter readings. In patients with cyanotic heart defect (e.g., coarctation of the aorta, interrupted aortic arch, pulmonary atresia, tetralogy of Fallot) or patent ductus, a preductal saturation is obtained in the right arm, and a postductal saturation is obtained in the left arm or in either foot for more accurate readings.
    Avoid sites distal to arterial lines or distal to noninvasive blood pressure cuffs.
  5. Apply the probe to the patient, ensuring that the light source is directly opposite the photodetector and the probe fits snugly without any gaps between it and the skin.
    Rationale: For accurate Sp O 2 measurement, the light source and the photodetector must be directly opposite each other.
    Do not apply the probe so tightly that it interrupts blood flow to or from the site. With a tight fit, tissue perfusion may be impaired by circumferential restriction of arterial flow or venous return. Venous congestion may lead to venous pulsations and false readings.
  6. Plug the oximeter into a grounded outlet, plug the cable into the oximeter or oximetry box or monitor, and plug the probe into the cable.
    Keep portable pulse oximeters plugged into an electrical outlet to keep the battery charged.
  7. Turn the oximeter or monitor on and allow an initializing period for detection and averaging of pulse rate and saturations.
    For spot-checking saturations, allow the oximeter several minutes of warm-up to average and obtain a reliable saturation reading.
  8. Set the appropriate pulse oximeter alarms for the patient’s baseline and upper limit saturation and baseline heart rate per the practitioner’s order or the organization’s practice. Make sure that alarms are turned on, functioning properly, and audible to health care team members.1
  9. Verify the accuracy of the pulse oximeter reading by correlating the patient’s heart rate to the reading from the pulse oximeter. Analyze the size and shape of the waveform and the height and fluctuation of the graphic display bar.
  10. Perform hand hygiene.
  11. Document the procedure in the patient’s record.

MONITORING AND CARE

  1. Assess the patient’s physiologic stability, including vital signs, respiratory status, and clinical appearance.
    Rationale: Pulse oximetry provides only one piece of data. Physiologic status must be considered to gain a complete assessment of the patient’s condition.
  2. Assess the probe site for breakdown and rotate the site per the organization’s practice or individual patient needs.
    Rationale: Skin probes have the potential to cause skin injury. Certain conditions (e.g., low perfusion states, use of vasoconstrictive infusions, hypoxia, hypotension, prolonged probe contact, prolonged arterial catheterization in the same extremity as the pulse oximeter probe, hypothermia) may increase the likelihood of injury.
  3. Assess, treat, and reassess pain.

EXPECTED OUTCOMES

  • SpO2 levels are continuously monitored.
  • Need for invasive monitoring of oxygenation status is reduced.
  • All periods of desaturation are identified and appropriate action is taken.
  • Incidences of false alarms are reduced.
  • Skin integrity is maintained.

UNEXPECTED OUTCOMES

  • Pulse oximetry saturation readings do not correlate with measured saturation from arterial blood gases.
  • An appropriate waveform is not displayed or the displayed heart rate and rhythm does not match the patient.
  • Patient decompensates without identification of changes in pulse oximetry.
  • Excessive motion or decreased tissue perfusion interferes with proper functioning of the pulse oximeter.
  • Pulse oximeter probe causes breakdown in skin integrity.

DOCUMENTATION

  • Pulse oximetry readings
  • Probe site selected with each probe change
  • Correlation of heart rate between patient and pulse oximetry
  • Condition of probe site
  • Episodes of desaturation, interventions, and recovery
  • Unexpected outcomes and related interventions
  • Education

REFERENCES

  1. Askie, L.M. and others. (2017). Effects of targeting higher versus lower arterial oxygen saturations on death or disability in preterm infants. Cochrane Database of Systematic Reviews, 4, Art. No.: CD011190. doi:10.1002/14651858.CD011190.pub2 (Level I)
  2. Aziz, K. and others. (2020). Part 5: Neonatal resuscitation: 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation, 142(16 Suppl. 2), S524-S550. doi:10.1161/CIR.0000000000000902 Retrieved February 1, 2021, from https://www.ahajournals.org/doi/10.1161/CIR.0000000000000902 (Level VII)
  3. Coe, K., Bradshaw, W.T., Tanaka, D.T. (2021). Chapter 7: Physiologic monitoring. In S.L. Gardner and others (Eds.), Merenstein & Gardner’s handbook of neonatal intensive care: An interprofessional approach (9th ed., pp. 165-185). St. Louis: Elsevier.
  4. Forest, S. (2021). Chapter 22: Care of the extremely low birth weight (ELBW) infant. In M.T. Verklan, M. Walden, S. Forest (Eds.), Core curriculum for neonatal intensive care nursing (6th ed., pp. 377-387). St. Louis: Elsevier. (Level VII)
  5. Fraser, D. (2021). Chapter 24: Respiratory distress. In M.T. Verklan, M. Walden, S. Forest (Eds.), Core curriculum for neonatal intensive care nursing (6th ed., pp. 394a-416). St. Louis: Elsevier. (Level VII)
  6. Pappas, B.E., Robey, D.L. (2021). Chapter 5: Neonatal delivery room resuscitation. In M.T. Verklan, M. Walden, S. Forest (Eds.), Core curriculum for neonatal intensive care nursing (6th ed., pp. 69-85). St. Louis: Elsevier. (Level VII)
  7. Verklan, M.T. (2021). Chapter 4: Adaption to extrauterine life. In M.T. Verklan, M. Walden, S. Forest (Eds.), Core curriculum for neonatal intensive care nursing (6th ed., pp. 54-68). St. Louis: Elsevier. (Level VII)

Elsevier Skills Levels of Evidence

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  • Level II - At least one well-designed randomized controlled trial
  • Level III - Well-designed controlled trials without randomization
  • Level IV - Well-designed case-controlled or cohort studies
  • Level V - Descriptive or qualitative studies
  • Level VI - Single descriptive or qualitative study
  • Level VII - Authority opinion or expert committee reports
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