Effect of lung volume reduction surgery on bony thorax configuration in severe COPD

Study objectives: Hyperinflation in patients with severe COPD is associated with an increased anteroposterior (AP) rib cage diameter. We sought to det ermine whether bilateral lung volume I eduction surgery (LVRS) affects bony thorax configuration, Design: Prospective of clinical data collection before and after LVRS. Setting: Tertiary-care university medical center. Patients: We measured multiple AP and transverse thoracic diameters, by usi ng plain chest roentgenograms (CXRs) in 25 patients (11 men, 14 women), and thoracic CT scans in 14 patients (7 men, 7 women), preoperatively and 3 mo nths postoperatively. A subgroup of 7 patients (reference data) also had CX R thoracic diameter measurements made, using films obtained previously with in a year of their presurgical evaluation. Another subgroup of 10 patients had CT scan measurements also made 12 months postoperatively, Measurements and results: CXR dimensions were taken at the level of the man ubrium sterni (hf) and thoracic T7 and T11 levels. CT dimensions were taken at T4, T6, T8, and T10 levels. At each level, left (L), midsagittal (C), a nd right (R) AP and maximal transverse diameters were measured. The sum of the three AP diameters (Total) was used for calculations. Patients also und erwent tests such as spirometry, lung volumes, diffusing capacity of the lu ng for carbon monoxide, 6-min walk distance (6MWD), and transdiaphragmatic pressures during maximum static inspiratory efforts (Pdimax sniff) measured before and 3 months after LVRS. Patients were (mean +/- SD) 58 +/- 8 years old, with severe COPD anti hyperinflation (FEV1, 0.68 +/- 0.23 L; FVC, 2.5 6 +/- 7.3 L; and total lung capacity [TLC], 143 +/- 22% predicted). After L VRS, AP diameters were reduced at thoracic level T7 (from 24.2 +/- 2.0 cm t o 23.3 +/- 2.2 cm, p = 0.0002), and transverse diameters were reduced at T7 (from 26.8 +/- 1.9 cm to 26.4 +/- 1.7 cm, p = 0.001) and T11 (from 29.9 +/ - 2.2 cm to 29.5 +/- 2.2 cm, p = 0.03), as measured using the CXR. In contr ast, thoracic diameters were similar in subjects with CXRs before LVRS and within 1 year before evaluation. CT-measured AP diameters were significantl y reduced 3 months after LVRS at T4, (from 48.8 +/- 6.0 cm to 46.7 +/- 5.4 cm, p = 0.02), T8 (from 54.2 +/- 7.0 cm to 52.3 +/- 6.5 cm, p = 0.004), and T10 (from 53.8 +/- 7.5 cm to 51.2 +/- 8.0 cm, p = 0.001), but not at Ti. T hese AP diameter reductions directly correlated with the postoperative redu ctions in TLC and residual volume, and also with the increases ill Pdimax s niff and 6MWD after LVRS. The reduction in AP diameters at thoracic levels T8 :Ind T10 seen 3 months after LVRS remained stable at 12-month follow-up, whereas those measured at T6 lost statistical significance. CT-measured tr ansverse diameters were unchanged at all levels after LVRS. Conclusions: We conclude that LVRS decreases mid-to-lower AP rib cage diame ter as assessed by CXR and thoracic CT. Although transverse diameters were reduced on CXR, the magnitude was small and was not confirmed with CT. Afte r LVRS, AP diameter reductions are most likely the result of reduction in l ung volume, and they are associated with improvements in diaphragm strength and exercise endurance.