this device also reports heart rate, may be a sensitive indicator of non-perfusing
dysrhythmias, and may indicate low cardiac output states. The waveform
visually demonstrates beat-to beat perfusion and, though subject to artifact such
as patient movement and electrical interference, is a sensitive indicator of
perfusion.
There are special considerations for the use of pulse oximetry in
neonates. In children with patent ductus arteriosus and with structural congenital
heart disease, arterial oxygen saturation may vary by location. Pre-ductal
saturation (right arm, right ear) reflects blood ejected through the aortic route or
equivalent which, in turn, is a mixture of blood returning from the lungs and blood
traversing intracardiac defects such as ASD and VSD. Post-ductal saturation
(lower extremities) reflects a mixture of blood ejected from the left ventricle and
systemic venous blood from the pulmonary artery. Thus, pre-ductal saturation is
a better tool to assess pulmonary function though the absolute value may be
affected by changes in intracardiac shunt. In contrast, post-ductal saturations
are indicative of the significance of pulmonary hypertension and the oxygen
content delivered to abdominal viscera.
B. Apnea and bradycardia monitoring
Premature infants (<36 weeks gestation and total gestational age <60wks)
frequently experience apnea and may become bradycardic as a result. This may
occur spontaneously, but is also a well-recognized consequence of illness,
operation/anesthesia, and physiologic stress. A chest strap detects chest wall