To evaluate the potential significance of a decreased thoracic AP diameter after LVRS on diaphragm strength, correlations with Pdimax sniff were made in eight patients who had transdiaphragmatic pressure measured (Fig 5). A strong relationship was observed between the postoperative decrease in AP diameter of the lower rib cage and the postoperative increase in diaphragm strength (r = 0.75, p = 0.03).
The potential significance of a decreased thoracic AP diameter on exercise endurance was also evaluated. Figure 6 correlates the percent change in AP diameter of the lower rib cage after LVRS, measured using plain CXR (at T11), and the percent change in distance walked during a 6MWD test. Again, a strong relationship is seen between the postoperative decrease in AP diameter of the lower rib cage and the postoperative increase in the distance walked in 6 min (r = 0.68, p = 0.01).
To determine whether the reductions in the mid-to-lower AP thoracic diameter initially observed 3 months after LVRS remained stable with time, a subgroup of 10 patients had thoracic CT scans also repeated 1 year after LVRS, and the same rib cage measurements were made. Table 7 demonstrates these measurements pre-operatively, and 3 and 12 months after LVRS. The AP diameter reductions initially seen 3 months after LVRS at T8 and T10 remained stable at 12 months; however, at T6 the reduction was no longer statistically significant. In these patients, FEV1 (36 vs 31% predicted) and TLC (109 vs 120% predicted) were no different at 12 months compared with 3 months after LVRS (p = 0.06 and 0.09, respectively). canadian neighbor pharmacy online
Our data confirm findings of prior investigations that LVRS improves spirometry, lung volumes, and diaphragm strength in select patients with severe COPD. They also demonstrate that LVRS alters the configuration of the bony thorax in these patients. Small but significant reductions in lower AP rib cage dimension are seen 3 months after LVRS, and are maintained at 1 year of follow-up. This configurational change significantly correlates with increases in diaphragm strength and exercise endurance, and may be the result of a postoperative reduction in lung volume.
Figure 5. Correlations between the percent change in AP diameter of the lower rib cage on CXR (at T11) after LVRS and the percent change in diaphragm strength (Pdimax sniff). This demonstrates that the post-LVRS reduction in lower AP diameter directly affects improvement in diaphragm strength.
Figure 6. Correlations between the percent change in AP diameter of the lower rib cage on CXR (at T11) after LVRS and the percent change in 6MWD. This demonstrates that the post-LVRS reduction in lower AP diameter directly affects improvement in performance during a 6MWD test.
Table 7—AP Thoracic Diameter at T6, T8, and T10 Before, 3, and 12 Months After LVRS (Using Thoracic CT Scans) (No. = 10)
|Rib Location||AP, cm||L, cm||C, cm||R, cm|
|Pre-LVRS||50.7 ± 3.8||17.5 ± 1.3||15.6 ± 1.5||17.5 ± 1.2|
|3-mo post-LVRS||48.1 ± 4.8t||16.3 ± 1.8t||15.0 ± 1.8||16.8 ± 1.6t|
|12-mo post-LVRS||47.8 ± 5.5J§||16.0 ± 2.9|§||15.1 ± 1.5j||16.7 ± 1.8|§|
|Pre-LVRS||51.5 ± 2.6||18.1 ± 1.4||15.7 ± 1.4||17.8 ± 1.6|
|3-mo post-LVRS||50.1 ± 2.6t||17.4 ± 1.3t||15.2 ± 1.4||17.3 ± 1.5|
|12-mo post-LVRS||49.5 ± 3.2|§||17.4 ± 1.4j||15.3 ± 1.4||17.4 ± 1.5|
|Pre-LVRS||46.8 ± 4.7||16.6 ± 1.5||14.0 ± 1.5||16.2 ± 1.8|
|3-mo post-LVRS||44.8 ± 4.6||15.8 ± 1.4||13.5 ± 1.6||15.5 ± 1.6t|
|12-mo post-LVRS||45.1 ± 3.7||15.9 ± 1.1||13.6 ± 1.4||15.6 ± 1.4|