Which of the following is not a reliable indicator of infant oxygenation status?

• A. Arterialized capillary sample
• B. Umbilical arterial line
• C. Pulse oximeter
• D. Transcutaneous electrode

Answer: (A)

Assessing an infant’s oxygenation status relies on measures that reflect systemic arterial oxygenation or tissue oxygen delivery. Arterialized capillary samples are not a reliable indicator because capillary blood reflects local perfusion and microcirculation rather than the whole-body arterial oxygenation. Factors such as peripheral perfusion, temperature, and regional blood flow can cause capillary PO2 and oxygen saturation to differ from arterial values, especially in sick or unstable neonates. In contrast, an umbilical arterial line provides direct arterial blood for accurate PaO2 and SaO2, pulse oximetry offers continuous noninvasive SpO2 monitoring, and a transcutaneous electrode provides ongoing estimates of tissue oxygenation. These modalities give a more dependable picture of the infant’s oxygenation status than a capillary sample.