Total lung capacity in a newborn is?

Appeared in: SJH Nursing Officer - 2019

Explanation

The total lung capacity (TLC) in a full-term newborn is approximately 150 mL.
TLC represents the maximum volume of air the lungs can contain after the deepest possible inhalation.
This value reflects the small size and developmental stage of the neonatal lungs compared to an adult's, which is around 5000-6000 mL.
Knowing this value is fundamental for understanding newborn respiratory function and providing appropriate care.

Option A: 100 ml is closer to the Functional Residual Capacity (FRC) of a newborn, which is the amount of air remaining in the lungs after a normal exhalation. It is not the total lung capacity.
Option B: 350 ml is an incorrect value that is more than double the actual total lung capacity of a newborn. It does not correspond to any standard neonatal lung volume.
Option C: 500 ml is the approximate tidal volume (the amount of air in a normal breath) for a healthy adult, not the total lung capacity of a newborn. This is a common distractor that confuses adult and neonatal values.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Neonatal respiratory physiology and lung volumes as background academic context rather than a clinical decision trigger.
Knowledge of neonatal lung volumes is critical for nurses, especially in the NICU, for setting appropriate ventilator parameters (like tidal volume and pressure) to prevent lung injury (barotrauma or volutrauma).
This understanding helps in the assessment of respiratory distress. A newborn with a lower-than-normal lung capacity may struggle to maintain adequate oxygenation, requiring intervention.
What if? If a newborn is premature (e.g., born at 30 weeks), their total lung capacity would be significantly less than 150 mL due to incomplete lung development and surfactant deficiency. This would necessitate immediate respiratory support with carefully titrated ventilation settings.

How to Approach the Question

This is a factual recall question testing knowledge of neonatal physiology.
Identify the key terms in the question: 'Total lung capacity' and 'newborn'.
Recall the standard physiological values for a term newborn's lung volumes from your studies.
Compare the recalled value with the given options.
Select the option that matches the known value, which is 150 mL.
Mentally differentiate this value from other lung volumes (like tidal volume or functional residual capacity) and from adult values to avoid selecting common distractors.

Concept Tested & Keywords

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E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 396-398

Practise the full SJH Nursing Officer - 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.