The Thoracic Inlet Index in patients with tracheal obstruction caused by chest wall deformity: Validation in patients and age-matched controls

AimWe present a novel index for evaluating severity of airway-threatening thoracic inlet compromise in childhood. Two indices were validated in three cases and sixty asymptomatic controls.MethodsWe developed an index to determine severity of thoracic inlet narrowing. Two different measurement methods were evaluated: Thoracic Inlet Index (TII) was determined at the site of greatest airway compromise at the level of the innominate artery crossing the anterior trachea and TII (anatomic) using purely skeletal measurements, both determined from thoracic CT scan. We sought to validate both indices to determine which was more predictive of the risk of airway compromise. Three patients who presented with life threatening airway compromise were compared to sixty age matched asymptomatic controls obtained from the trauma registry.ResultsThe mean TII in controls was 3.89. The TII was consistent at various ages. In patients, mean TII was 12.16 (range of 11.31-12.95). For TII the difference between controls and symptomatic patients was highly significant (P = 0.0012). The mean TII (anatomic) in controls was 3.5. The TII (anatomic) was less consistent when evaluated in different age groups. In patients mean TII (anatomic) was 6.32 (range 5.38-7.59). For TII (anatomic), the difference between controls and symptomatic patients was also significant (P = 0.0474) but did not discriminate as well as the functional index.ConclusionsThe TII measured at the level of the innominate artery crossing on thoracic CT scan appears to be the most useful. A level of greater than 10 was highly predictive of airway compromise in our patient group.