Some parents notice that during an asthma attack, their child’s chest doesn’t bulge outward as it normally would — instead, the chest caves in when they inhale deeply. This abnormal respiratory movement is medically called paradoxical breathing.

Normally, inhaling causes the chest cavity to expand, accompanied by outward movement of the chest wall. However, in cases of paradoxical breathing, the lower chest wall retracts inward during inhalation. This occurs because during an asthma attack, the child takes rapid, forceful breaths, creating a strong negative pressure in the thoracic cavity. Since the chest wall bones of infants and young children are incompletely developed, with the lower anterior chest wall remaining relatively unstable and more pliable, this area may displace significantly during an asthma attack.

If paradoxical breathing recurs persistently and remains uncontrolled, it may gradually deform the chest wall structure — causing sternal depression and ultimately leading to pectus excavatum.

Paradoxical breathing serves not only as a warning sign of potential chest wall abnormalities, but may also lead to hypoxia and impaired cardiopulmonary function. In severe cases, it can even be life-threatening. Therefore, early recognition of paradoxical breathing and aggressive asthma control are crucial to preventing pectus excavatum.