Friday July 31, 2009 (pediatric pearl)
Uniqueness of Pediatric Lower Airway
The frequency of acute respiratory failure is higher in infants and young children than in adults for several reasons. This difference can be explained by defining anatomic compartments and their developmental differences in pediatric patients that influence susceptibility to acute respiratory failure.
The respiratory pump includes the nervous system with central control (ie, cerebrum, brainstem, spinal cord, peripheral nerves), respiratory muscles, and chest wall. Features of note in pediatric patients include the following:
- The respiratory center is immature in infants and young children and leads to irregular respirations and an increased risk of apnea.
- The ribs are horizontally oriented. During inspiration, a decreased volume is displaced, and the capacity to increase tidal volume is limited compared with that in older individuals.
- The small surface area for the interaction between the diaphragm and thorax limits displacing volume in the vertical direction.
- The musculature is not fully developed. The slow-twitch fatigue-resistant muscle fibers in the infant are underdeveloped.
- The soft compliant chest wall provides little opposition to the deflating tendency of the lungs. This leads to a lower functional residual capacity in pediatric patients than in adults, a volume that approaches the pediatric alveolus critical closing volume.