Assessment of pectus excavatum using thoracic calipers

Assessment of PE using thoracic calipers. Measurements are generally performed during quiet breathing rather than maximal inspiration or expiration.
(A) Measurement at maximal sternal depression.
(B) Measurement of thoracic width.
The ratio of B:A is analogous to the CT-based PSI. However, there are no standards for defining PE severity using caliper measurements, and they cannot be used as a substitute for PSI. The primary use of caliper measurements is to document the deformity and monitor changes over time.