A small degree of inflammation in a child's airway can lead to a disproportionately large increase in airway resistance compared to an adult. Which of the following is the primary reason for this?
Children have a higher metabolic rate, which increases their oxygen demand.
The infant's trachea is more cartilaginous and flexible, leading to easier collapse.
Children rely more on their diaphragm for breathing, making them less efficient at clearing secretions.
The child's airway has a significantly narrower diameter, so a small reduction in radius leads to a large increase in resistance.
The Correct Answer is D
The primary reason a small degree of inflammation in a child’s airway causes a disproportionately large increase in airway resistance is the significantly narrower airway diameter. According to Poiseuille’s law, resistance to airflow is inversely proportional to the fourth power of the radius, meaning even a slight reduction in airway size greatly increases resistance.
Rationale for correct answer:
4. A child’s airway is much narrower than an adult’s, so swelling or mucus buildup reduces the radius substantially, causing a dramatic increase in resistance and work of breathing. This makes conditions like croup or bronchiolitis more severe in young children.
Rationale for incorrect answers:
1. While children do have higher metabolic rates and oxygen demands, this is not the main reason for the exaggerated effect of inflammation on airway resistance.
2. The cartilaginous and flexible trachea in infants contributes to collapsibility but does not explain the disproportionate rise in resistance from swelling.
3. Greater diaphragmatic reliance affects breathing mechanics but not the mathematical relationship between airway narrowing and resistance.
Take home points
- Airway resistance is highly sensitive to changes in radius, especially in children due to their small baseline diameters.
- Even minor airway swelling (e.g., 1 mm circumferential edema) can reduce the cross-sectional area by more than half in a child.
- Rapid recognition and management of pediatric airway inflammation is critical to prevent respiratory distress and hypoxia.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
The mucociliary clearance system is a key innate defense mechanism of the respiratory tract, designed to trap and remove inhaled particles, pathogens, and debris before they reach the lower airways and alveoli.
Rationale for correct answer:
1. The respiratory epithelium contains mucus-producing goblet cells and ciliated cells. Mucus traps inhaled contaminants, and coordinated ciliary beating moves the mucus upward toward the pharynx, where it can be swallowed or expectorated. This process helps prevent infections and maintains airway cleanliness.
Rationale for incorrect answers:
2. While moisture in the alveoli facilitates gas exchange, this is not the main role of the mucociliary clearance system, alveolar moisture regulation is handled by surfactant and fluid balance mechanisms, not cilia and mucus.
3. Adaptive immunity involves lymphocytes and antigen-specific responses, which are separate from the mechanical clearance provided by the mucociliary system.
4. Angiotensin-converting enzyme (ACE) production occurs mainly in the pulmonary capillary endothelium, not as part of mucociliary clearance.
Take home points
- The mucociliary escalator is an essential first-line defense in the respiratory tract.
- Smoking, dehydration, and certain diseases (e.g., cystic fibrosis, primary ciliary dyskinesia) can impair this system, increasing infection risk.
- Efficient mucociliary function is especially important in children, whose immune systems are still developing.
Correct Answer is ["A","B","C"]
Explanation
Infants and children have multiple anatomical and physiological characteristics that increase their vulnerability to respiratory distress and disease. These features make them less able to compensate for airway compromise, infection, or increased oxygen demands.
Rationale for correct answers:
1. Fewer and smaller alveoli: At birth, the lungs have a limited number of alveoli, which grow in number and size over early childhood. This reduces the surface area for gas exchange, making them more prone to hypoxia during illness.
2. More compliant, cartilaginous chest wall: A softer chest wall can lead to retractions and inefficient ventilation when respiratory effort increases.
3. Higher, more anterior larynx: This anatomical position makes airway obstruction more likely and complicates airway management during resuscitation or intubation.
Rationale for incorrect answers:
4. Infants actually have a higher metabolic rate and oxygen consumption (about twice that of adults per kg body weight). This increases their vulnerability to hypoxia when breathing is compromised.
Take home points
- Pediatric airways are smaller, more collapsible, and more easily obstructed than adult airways.
- Immature lung development limits gas exchange capacity.
- High oxygen needs and low reserves mean children can deteriorate rapidly.
- Early recognition and intervention are essential to prevent severe hypoxia.
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