Normal values for a healthy 6-month-old, 7-kg infant include which of the following?

Normal values for a healthy 6-month-old, 7-kg infant include which of the following?

• A. Hemoglobin 17 g/dL
• B. Heart rate 90 beats/min
• C. Respiratory rate 20 breaths/min
• D. O2 consumption at rest 35 mL/min

Answer: (D)

Oxygen use at rest scales with body size, and infants have a relatively high metabolic rate per kilogram. For a healthy 6-month-old around 7 kg, resting oxygen consumption is typically about 4–6 mL of O2 per kilogram per minute. Multiplying by 7 kg gives roughly 28–42 mL/min, with around 35 mL/min being a representative value. That matches the given rest-state oxygen consumption. Other values don’t fit typical pediatric norms. Hemoglobin for a 6-month-old is usually in the 11–14 g/dL range; 17 g/dL would be unusually high. Resting heart rate in a young infant is commonly about 100–160 bpm, not as low as 90, and respiratory rate is generally about 30–60 breaths per minute, not 20. So the O2 consumption at rest around 35 mL/min is the one that aligns with normal physiology for this age and size.

Oxygen use at rest scales with body size, and infants have a relatively high metabolic rate per kilogram. For a healthy 6-month-old around 7 kg, resting oxygen consumption is typically about 4–6 mL of O2 per kilogram per minute. Multiplying by 7 kg gives roughly 28–42 mL/min, with around 35 mL/min being a representative value. That matches the given rest-state oxygen consumption.

Other values don’t fit typical pediatric norms. Hemoglobin for a 6-month-old is usually in the 11–14 g/dL range; 17 g/dL would be unusually high. Resting heart rate in a young infant is commonly about 100–160 bpm, not as low as 90, and respiratory rate is generally about 30–60 breaths per minute, not 20. So the O2 consumption at rest around 35 mL/min is the one that aligns with normal physiology for this age and size.