What are retractions and why do they occur?
Normally, inspiration is almost effortless. When airway resistance is high, a child must generate greater negative intrathoracic pressure to draw air into the lungs. That requires greater work of breathing, which can be seen as greater muscular activity of the neck, chest, and abdominal musculature. Flaring of the nostrils may also be noted when respiratory distress is severe. When intrathoracic pressure is very negative, parts of the chest retract inward. These retractions may be seen just below the costal margin (subcostal), just above the sternum (suprasternal), or between the ribs (intercostal). Retractions are a very important clinical finding even in the absence of wheezing or rales, because a child with impending or existing respiratory failure may have retractions without enough airflow to generate audible abnormal breath sounds.