activity have yet to be defined. Therefore, while the clinician may obtain an ever-
expanding data set with regard to neurologic function in the neonate, enthusiasm
must be matched with skepticism regarding the validity of any specific values.
III. Respiratory Monitoring
A. Pulse Oximetry
Prior to the development of modern continuous pulse oximetry, hypoxemia
and it’s related complications were frequent events in the neonatal and pediatric
ICU environments. Pulse oximetry makes use of the principle that hemoglobin
saturated with oxygen (or other gases) will exhibit different absorbance and
transmittance characteristics for specific wavelengths of light. By testing normal
patients in the range of tolerable oxygen saturation (75-100%) and inferring the
characteristics at lower saturations, manufacturers built algorithms to report
continuous oxygen saturation that approximated arterial blood gas
measurements to within 2-5 percent in the higher ranges and 10% at the lower
ranges. However, early devices used single wavelengths of light and could only
differentiate ‘saturated’ from unsaturated hemoglobin. Furthermore, they
required pulsatile blood flow to differentiate arterial from venous signals and
could not be used during ECLS. The addition of two more wavelengths has
resulted in absolute values that reliably lie within 2% of blood gas measurements
and can accurately report total hemoglobin, methemoglobin, and
carboxyhemoglobin concentrations on a continuous basis.