Upper thoracic shape in children with pectus excavatum: impact on lung function

Pectus excavatum (PE) can present with respiratory complaints in childhood. However severity of the PE, measured by the Pectus Severity Index (PSI), correlates only modestly with reduced vital capacity (VC). We hypothesized that another upper thoracic feature, a pectus gracilis (PG) or slender chest, co-exists with PE, and impacts lung function.

We developed the Pectus Gracilis Index (PGI) based on the chest width to depth ratio at the gladiolar-manubrial sternal junction on computerized tomographic (CT) scans, and measured PGI among 316 control children 10-20 years old. PG was defined by PGI values >2 z-scores above the mean normal value. We determined the prevalence of PG in 97 children with PE and correlated PGI and PSI with VC among the 86 that performed spirometry.

The mean and upper limit of normal for PGI averaged 2.73 and 3.55, respectively for control children. The prevalences of a PG among controls and children with PEs were 3.2% and 59%, respectively (OR = 45, P < 0.00001). Among the children with PEs, the PGI, and PSI correlated with one another (r = 0.77, P < 0.001). Both PSI and PGI significantly correlated inversely with VC. (r = -0.34, P < 0.001 and r = -0.38, P < 0.001, respectively). Importantly, PGI correlated with VC after adjusting for PSI among children with PE. (r = 0.20, P < 0.03).

The upper thoracic feature of a PG is common among children with PE and contributes to reductions in VC. Assessment of the thorax, using the PGI, may improve the structure-function correlations previously described for children with PE.