Ribcage deformity and the altered breathing pattern in children with osteogenesis imperfecta

Osteogenesis Imperfecta (OI) is a genetic disease characterized by bones fragility and progressive deformity. Life expectancy is reduced in the non-lethal most severe type III form before the age of 10 years. The main cause of death in OI is respiratory insufficiency resulting from impaired thoracic function worsened by ribcage deformity and scoliosis.

We used opto-electronic plethysmography to study chest geometry, the ventilatory, and the thoraco-abdominal pattern at rest in supine position in children younger than 10 years. Radiographic measurements were used to describe spinal deformity.

Eight severe OI (sOI), seven affected by other moderate forms (mOI), and nine healthy controls (CTR) were analyzed. sOI were characterized by Pectus carinatum (sternal angle: 165.2°, CTR: 183.1°; P < 0.01), rapid and shallow breathing (RSBi: 267.4 L^-1 min^-1 , CTR: 150.7 L^-1 min^-1 ; P < 0.05) and reduced pulmonary rib cage contribution to tidal volume (5.1%, CTR: 14.6%; P < 0.001) that evolved with age approaching the paradoxical inspiratory inward movement previously found in adults. mOI showed almost normal ventilatory pattern (RSBi: 189.2^-1 min^-1 ) and absence of sternal deformity (sternal angle: 176.8°). Platyspondyly and kyphosis were common features in all OI children.

An altered breathing pattern in severe OI is present since childhood and it worsens with age. This is caused by the combination of pectus carinatum, brittle ribs and spinal deformity that put the ribcage muscles in mechanical disadvantage. These results suggest that in severe OI the assessment of the respiratory function should start in early childhood in order to try to reduce the incidence of premature death.