Improvement of dyspnea sensation after lung volume reduction surgery and perceived site of dyspnea in severe pulmonary emphysema

本研究从以下几个方面探讨了重度肺气肿患者行肺减容术（LVRS）后呼吸困难改善的机制：1）运动时呼吸困难的评估：LVRS后肺功能明显改善：FEV_1增加，肺活量增加，残气量减少，PaO_2增加，PaCO_2降低，FRC降低。LVRS后，通过递增负荷评估的最大运动能力和通过博格量表评估的运动期间呼吸困难感觉也得到改善。呼吸肌氧耗量测定：采用连续死腔负荷法测定呼吸肌氧耗量，结果显示LVRS后呼吸肌氧耗量较LVRS前明显降低。3）生存预后：LVRS组术后1年和3年生存率分别为91%和78%。确诊后1年和3年非手术组和严重程度匹配组的生存率分别为93%和64%。4）影响生存预后的因素：LVRS前低氧血症程度、弥散功能、营养状况等因素影响预后。高碳酸血症不是手术的限制因素。对高碳酸血症的缓解反应降低的患者病情更严重。5）肺气肿患者呼吸困难的感知部位：我们发现正常受试者在吸气阻力负荷期间，通过正电子发射断层扫描评估的部分运动区和/或扣带回皮质的葡萄糖代谢增强。这些部位可能是造成呼吸困难感觉的原因。然而，这项研究尚未扩展到肺气肿患者。

We studied the mechanisms of the improvement of dyspnea after lung volume reduction surgery (LVRS) in severe pulmonary emphysema with regard to the following aspects :1) Estimation of dyspnea during exercise : Pulmonary functions after LVRS improved significantly as follows : FEV1 increased, vital capacity increased, residual volume decreased, PaO2 increased, PaCO2 decreased and FRC decreased. Maximal exercise capacity estimated by incremental loading and dyspnea sensation during exercise estimated by Borg scale also improved after LVRS. There was a significant correlation between decrease in FRC (ΔFRC) and improvement of dyspnea (ΔBorg).2) Measurement of respiratory muscle oxygen consumption : Respiratory muscle oxygen consumption assessed by continuous dead space loading as developed previously by us decreased after LVRS in comparison with the corresponding ventilation before LVRS. This result may indicate an improvement of ventilatory efficiency.3) Survival prognosis : Survival rates of LVRS patients' group were 91 and 78% at 1 and 3 years after surgery, respectively. Survival rates of non-surgical and severity-matched patients' group were 93 and 64% at 1 and 3 years after determination of the diagnosis. The difference between these two survival rates was significant.4) Factors affecting the survival prognosis : The prognosis was affected by such factors as the degree of hypoxemia, diffusing capacity and nutrition before LVRS. Hypercapnia is not a limiting factor for surgery. Patients with a decreased ventilatory response to hypercapnia had worse prognoses.5) Perceived site of dyspnea in pulmonary emphysema : We found that normal subjects had an enhancement of glucose metabolism assessed by positoron emission tomography in a part of the motor area and/or cingulate cortex during inspiratory resistive loading. These sites may be responsible for the dyspnea sensation. However, this study has not been extended to patients with pulmonary emphysema.