Preoperative severity of emphysema predictive of improvement after lung volume reduction surgery: use of CT morphometry.
OBJECTIVE
To determine how the volume and severity of emphysema measured by CT morphometry (CTM) before and after lung volume reduction surgery (LVRS) relates to the functional status of patients after LVRS.


METHODS
A histologically validated CT algorithm was used to quantify the volume and severity of emphysema in 35 patients before and after LVRS: total lung volume (TLV), normal lung volume (< 6.0 mL gas per gram of tissue), volume of mild/moderate emphysema (ME; 6.0 to 10.2 mL gas per gram of tissue), volume of severe emphysema (> 10.2 mL gas per gram of tissue), surface area/volume (SA/V; meters squared per milliliter), and surface area (SA; meters squared). Outcome parameters included maximal cardiopulmonary exercise (CPX) performance in 21 patients and routine pulmonary function in all patients. We hypothesized that baseline CTM parameters predict response to LVRS and that the change in these parameters may offer insight into mechanisms of improvement.


METHODS
Thirty-five patients with severe emphysema who had successful LVRS.


RESULTS
The significant decrease in TLV following LVRS was entirely accounted for by a decrease in severe emphysema. The SA/V and the SA both increased significantly following LVRS. The change in maximal CPX in watts following surgery correlated significantly with baseline values of severe emphysema (r = 0.60), which was collinear with TLV, and SA/V. The change in diffusing capacity of the lung for carbon monoxide revealed a significant positive linear relationship with preoperative severe emphysema (r = 0.37) and a negative relationship with ME (r = -0.37). Change in watts revealed a strong relationship with changes in severe emphysema (r = -0.75) and weaker but significant relationships with change in TLV, ME, SA/V, and SA. Other measures of pulmonary function revealed significant albeit less dominant relationships with baseline CTM and change in these indexes.


CONCLUSIONS
Using CTM, we have identified a close relationship between baseline severe emphysema, or change in severe emphysema, and the improvement in CPX after LVRS. These observations support a potential role of CTM in future clinical trials for predicting responders to LVRS and identifying mechanisms of improvement.
Rogers
R M
RM
Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, University of Pittsburgh Medical Center and School of Medicine, Pittsburgh, PA, USA. rogersrm@msx.upmc.edu
Coxson
H O
HO
Sciurba
F C
FC
Keenan
R J
RJ
Whittall
K P
KP
Hogg
J C
JC
D000465:Algorithms; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D005544:Forecasting; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D011013:Pneumonectomy; D011653:Pulmonary Diffusing Capacity / Q000502:physiology; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D012115:Residual Volume / Q000502:physiology; D014057:Tomography, X-Ray Computed; D014109:Total Lung Capacity / Q000502:physiology; D016896:Treatment Outcome; D014797:Vital Capacity / Q000502:physiology