Final answer:
A term neonate with different right hand (99%) and left foot (89%) SpO2 readings may indicate a congenital heart defect or other issue, necessitating further diagnostic evaluations and interventions.
Step-by-step explanation:
A term neonate exhibiting a significant difference in SpO2 readings between the right hand (99%) and left foot (89%) after an oxygen challenge test may be demonstrating signs of a congenital heart defect such as ductal-dependent congenital heart disease or neonatal pneumonia. The SpO2 readings are obtained using a pulse oximeter, which sends red and infrared wavelengths of light through body tissue to calculate oxygen saturation in the hemoglobin based on light absorption. The normal range for SpO2 is between 95-100 percent, and the discrepancy in the readings between the limbs (>10%) suggests a possible difference in pre- and post-ductal oxygen saturation that needs further investigation.
Based on this information, the most appropriate recommendation would be to undertake immediate further diagnostic evaluations, such as an echocardiogram and possibly an arterial blood gas test, to assess the cause of the hypoxemia and administer appropriate interventions, possibly including supplemental oxygen or more specific treatments depending on the underlying cause.