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

我们从以下几个方面研究重症肺气肿肺减容手术后呼吸困难改善的机制：1)运动时呼吸困难的评估：肺减容手术后肺功能明显改善，FEV1增加，肺活量增加，残气量减少，PaO2增加，PaCO2降低，FRC降低。增加负荷估计的最大运动能力和Borg量表估计的运动时呼吸困难感在LVRS后也有改善。FRC的减少（ΔFRC）与呼吸困难的改善（ΔBorg）之间存在显著相关性。2)测量呼吸肌耗氧量：我们之前制定的连续死区负荷法评估的呼吸肌耗氧量在LVRS后较LVRS前相应通气降低。这一结果可能表明通风效率的提高。3)生存预后：LVRS患者组术后1年和3年生存率分别为91%和78%。确诊后1年和3年，非手术组和严重匹配组的生存率分别为93%和64%。这两种存活率之间的差异是显著的。4)影响生存预后的因素：LVRS前低氧血症程度、弥散能力、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。高碳酸血症通气反应降低的患者预后较差。5)肺气肿呼吸困难的感知部位：我们发现，在吸气阻力负荷时，正常受试者的部分运动区和/或扣带皮层的正电子发射断层扫描评估了葡萄糖代谢的增强。这些部位可能与呼吸困难的感觉有关。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.