Study objectives: The aim of this study was to
investigate prospectively the changes in neural drive to the diaphragm
in the first year after lung volume reduction surgery (LVRS) in
patients with COPD.
Patients and methods: In 14
patients with severe emphysema (mean ± SD; age, 53.7 ± 8.3 years;
FEV1, 0.64 ± 0.18 L; residual volume [RV],
5.33 ± 1.25 L; Pao2, 62.3 ± 9.0 mm Hg;
Paco2, 39.0 ± 6.0 mm Hg), we assessed lung
function, arterial blood gases, maximal exercise capacity (Wmax), and
oxygen uptake (V̇o2max); intrinsic
positive end-expiratory pressure (PEEPi); diaphragmatic strength
(transdiaphragmatic pressure, Pdisniff) and endurance capacity (tlim);
central diaphragmatic drive assessed by root mean square analysis of
the esophageal electromyogram (rmsdia); and isotime dyspnea during
loaded breathing tests (BS).
Results: Despite a
significant increase (expressed as a percentage of baseline) in
FEV1 (40.6%) and a decrease in RV (30.0%) and PEEPi
(75.7%) 1 month after LVRS, the improvements in Wmax (31.2%) and
V̇o2max (13.7%); Pdisniff (25.4%)
and tlim (64.9%); rmsdia (34.6%); and BS (21.7%) did not reach
statistical significance (p < 0.05) until 6 months after LVRS.
Arterial blood gases did not change significantly. Significant
correlations were found between decrease in rmsdia and changes in PEEPi
(r = 0.69), Wmax (r = −0.56), Pdisniff (r = −0.65), tlim
(r = −0.59), and BS (r = 0.71) 6 months after LVRS.
Conclusions: Our results show that LVRS is able to increase
the efficacy of the respiratory pump and by this way reduce ventilatory
drive and respiratory effort sensation.