Final answer:
The most sensitive indicator of a child's O2 supply is respiratory rate, which is a critical part of the Apgar score assessment for newborns.
Step-by-step explanation:
The most sensitive indicator of a child's O2 supply is respiratory rate. In assessing the O2 supply of newborns, the Apgar score is commonly used. The Apgar score includes five criteria: skin color, heart rate, reflex, muscle tone, and respiration. Scores are assigned from 0 to 2 for each criterion and are taken at 1 minute and again at 5 minutes after birth. Heart rate and respiration are the most critical measurements in this score, with poor scores indicating the potential need for immediate medical intervention.
While a pulse oximeter can measure the amount of oxygen in the blood, blood pressure and temperature are not as directly linked to oxygen supply as heart rate and respiration. Respiratory activity is heavily influenced by blood levels of oxygen, and peripheral chemoreceptors in the body detect significant changes in these levels, which can then lead to an increase in the respiratory rate.