66 Section II ■ Physiologic Monitoring

(5) Because the measurements of the change in

absorption are made during a pulse (systole), these

pulses are counted and displayed as heart rate.

C. Indications

1. Noninvasive continuous or intermittent arterial oxygen

saturation and heart rate monitoring

2. To monitor oxygenation in infants suffering from conditions associated with

a. Hypoxia

b. Apnea/hypoventilation

c. Cardiorespiratory disease

d. Bronchopulmonary dysplasia

3. To monitor response to therapy

a. Resuscitation

 Pulse oximetry is a necessary adjunct to monitoring in the delivery room. With the use of pulse

oximetry, SpO2 values can be obtained within

1 minute after birth (4–8) (Fig. 10.4).

b. Monitoring effectiveness of bag and mask ventilation or during placement of an endotracheal tube

4. To monitor side effects of other therapy

a. Endotracheal tube suctioning

b. Positioning for laryngoscopy, spinal tap, etc.

Fig. 10.1. Arterial PO2 versus pulse oximeter percent saturation

in near-term newborn infants in whom pulse saturation was fixed

by adjusting FiO2 first and then measuring PaO2. Values are means

± SD. (From Brockway J, Hay WW Jr. Ability of pulse O2 saturations to accurately determine blood oxygenation. Clin Res. 1988;

36:227A, with permission.)

Fig. 10.2. Factors affecting hemoglobin–oxygen affinity. 2,3-

DPG, 2,3-diphosphoglycerate. (From Hay WW Jr. Physiology of

oxygenation and its relation to pulse oximetry in neonates. J

Perinatol. 1987;7:309, with permission.)

Fig. 10.3. Tissue composite showing dynamic as well as static

components affecting light absorption. (From Wukitch MW, Petterson

MT, Tobler DR, et al. Pulse oximetry: analysis of theory, technology

and practice. J Clin Monit. 1988;4:290, with permission.)

d. The different absorption of the wavelengths when

transmitted through tissue, pulsatile blood, and nonpulsatile blood are utilized (Fig. 10.3).

(1) The photodetector measures the level of light

that passes through without being absorbed.

(2) During the absence of pulse (diastole), the detector establishes baseline levels for the wavelength

absorption of tissue and nonpulsatile blood.

(3) With each heartbeat, a pulse of oxygenated

blood flows to the sensor site.

(4) Absorption during systole of both the red and

the infrared light is measured to determine the

percentage of oxyhemoglobin.

Fig. 10.4. Mean arterial oxygen saturation (SaO2) values measured by pulse oximetry from the time of cord clamping. Values

are means ± SD. (From House JT, Schultetus RR, Gravenstein N.

Continuous neonatal evaluation in the delivery room by pulse

oximetry. J Clin Monit. 1987;3:96, with permission.)

Chapter 10 ■ Continuous Blood Gas Monitoring 67

5. For extremely low-birthweight infants <1,000 g (9–11)

 It is optimal to use pulse oximetry for oxygen monitoring in the very low-birthweight infant because of its

noninvasiveness. Pulse oximetry can be used reliably in

very low-birthweight infants with acute as well as

chronic lung disease (9–11).

6. Pulse oximetry also offers an advantage for precise fraction of inspired oxygen (FiO2) control during neonatal

anesthesia because of the short response time to

changes in SpO2 (10).