Effects of Lung Volume Reduction Surgery for Emphysema on Diaphragm Dimensions and Configuration

Abstract

Part of the functional benefit provided by lung volume reduction surgery (LVRS) may be related to improvement in respiratory muscle function resulting from changes in diaphragm dimension and configuration. To study these changes, we obtained 3D reconstructions of the muscle using spiral computed tomography in 11 patients with severe emphysema before and 3 mo after surgery, and in 11 normal subjects matched for sex, age, height, and weight. Bilateral LVRS was performed by thoracoscopy in eight patients and by sternotomy in three patients. Acquisitions were made in the supine posture at relaxed FRC, midinspiratory capacity, and TLC. On average, LVRS produced a 51 +/- 11% increase in FEV(1) and a 30 +/- 4% decrease in FRC. The total surface area of the diaphragm (A(di)) and of the zone of apposition (A(ap)) at FRC increased by 17 +/- 4% and 43 +/- 8%, respectively, but the surface area of the dome did not change. Compared with the values recorded in the normal subjects, postoperative values of A(di) and A(ap) at FRC were reduced by 11% (p < 0.05) and 24% (p < 0.005), respectively. The curvature of the dome increased at TLC in the left sagittal plane, but was otherwise unaffected by the procedure. We conclude that LVRS substantially increases A(di) and A(ap), but does not significantly improve diaphragm configuration at FRC.

Treatment of chronic respiratory failure: lung volume reduction surgery versus rehabilitation

“…In general, inspiratory muscle function (PI,max and maximal transdiaphragmatic pressure) also improved, confirming the results of more-targeted studies [74][75][76]. The improvements in inspiratory muscle function are probably due to geometric factors rather than intrinsic improvements in inspiratory muscle function [77,78]. LVRS is unique in the sense that it is the only procedure that causes substantial improvements in lung function in end-stage emphysema, besides lung transplantation.…”

“…A comprehensive discussion is clearly beyond the scope of the present publication, and has already been published [79]. The hypotheses explaining the improvement include: improved lung mechanics, increased lung elastic recoil [80,81], reduced intrinsic positive inspiratory pressure [82], reduced hyperinflation, increased respiratory muscle strength due to geometric factors [74][75][76][77][78], improved ventilation/perfusion matching, and reduced pulmonary vascular resistance. There is evidence that the major mode of action is resizing of the lungs [83][84][85][86].…”

Physiologic Basis for Improved Pulmonary Function after Lung Volume Reduction

“…This has also been shown specifically for the diaphragm, measured by maximal transdiaphragmatic pressure during sniffs, inspiratory/expulsive maneuvers, and phrenic stimulation (19). Cassart and colleagues used threedimensional reconstruction of the diaphragm from computed tomography scans to show that LVRS increased the zone of apposition, which would improve the mechanical efficiency of inspiration (29). Increased zone of apposition has also been as- Figure 1.…”

Influence of the distribution of emphysema on diaphragmatic motion in patients with chronic obstructive pulmonary disease

“…22,25 The zone of apposition, measured by ΔLappo, plays an important role in the pressure-generating ability of the diaphragm. 22,25,26 Mpr(%) represents the ratio of wasteful and ineffective motion of the diaphragm for respiration. 14 Thus, these factors mainly assess the contribution of the diaphragm to chest wall motion.…”