Palange P, Forte S, Onorati P, Paravati V, Manfredi F, Serra P, Carlone S
Dipartimento di Medicina Clinica, University of Rome La Sapienza, Italy.
Chest. 1998 Jul;114(1):12-8. doi: 10.1378/chest.114.1.12.
Reduced muscle aerobic capacity in COPD patients has been demonstrated in several laboratories by phosphorus magnetic resonance spectroscopy and by analysis of oxygen uptake (VO2) kinetics. COPD patients are usually elderly, hypoxemic, poorly active with muscle atrophy, and often malnourished. Under these conditions there is usually reduction of O2 delivery to the tissues (bulk O2 flow), redistribution of fiber type within the muscle, capillary rarefaction, and decreased mitochondrial function, alterations all capable of reducing muscle aerobic capacity. In COPD, the effect of reduced body mass on muscle aerobic capacity has not been investigated (to our knowledge).
We studied 24 patients with stable COPD with moderate-to-severe airway obstruction (68+/-5 [SD] years; FEV1, 39+/-12% predicted; PaO2, 66+/-8 mm Hg; PaCO2, 41+/-3 mm Hg) with poor to normal nutritional status, as indicated by a low-normal percent of ideal body weight (IBW). Each subject first underwent 1-min maximal incremental cycle ergometer exercise for determination of VO2 peak and lactate threshold (LT). Subsequently, they performed a 10-min moderate (80% of LT-VO2) constant load exercise for determination of oxygen deficit (O2DEF) and mean response time VO2 (MRT). VO2, CO2 output (VCO2), and minute ventilation were measured breath by breath.
Patients displayed low VO2 peak (1,094+/-47 [SE] mL/min), LT-VO2 (35+/-3% predicted O2 max), and higher MRT-VO2 (67+/-4 s). Univariate regression analysis showed that percent of IBW correlated with indexes of maximal and submaximal aerobic capacity: vs VO2 peak, R=0.53 (p<0.01); vs MRT R=-0.77 (p<0.001). Using stepwise regression analysis, MRT correlated (R2=-0.70) with percent of IBW (p<0.01) and with PaO2 (p<0.05).
Reduced body mass has an independent negative effect on muscle aerobic capacity in COPD patients: this effect may explain the variability in exercise tolerance among patients with comparable ventilatory limitation.
多个实验室已通过磷磁共振波谱法以及对氧摄取（VO₂）动力学的分析证实，慢性阻塞性肺疾病（COPD）患者的肌肉有氧能力下降。COPD患者通常年事已高、存在低氧血症、活动能力差且伴有肌肉萎缩，还常常营养不良。在这些情况下，通常会出现组织氧输送（总体氧流量）减少、肌肉内纤维类型重新分布、毛细血管稀疏以及线粒体功能降低，所有这些改变都可能降低肌肉有氧能力。据我们所知，在COPD中，体重减轻对肌肉有氧能力的影响尚未得到研究。
我们研究了24例稳定期COPD患者，他们存在中度至重度气道阻塞（年龄68±5[标准差]岁；第1秒用力呼气容积[FEV₁]为预计值的39±12%；动脉血氧分压[PaO₂]为66±8 mmHg；动脉血二氧化碳分压[PaCO₂]为41±3 mmHg），营养状况从较差到正常，这由理想体重（IBW）的低正常百分比表示。每位受试者首先进行1分钟的最大递增功率自行车运动，以测定VO₂峰值和乳酸阈（LT）。随后，他们进行10分钟的中等强度（LT-VO₂的80%）恒定负荷运动，以测定氧亏缺（O₂DEF）和VO₂平均反应时间（MRT）。逐次测量VO₂、二氧化碳排出量（VCO₂）和分钟通气量。
患者表现出较低的VO₂峰值（1094±47[标准误]mL/分钟）、LT-VO₂（为预计最大摄氧量的35±3%）以及较高的MRT-VO₂（67±4秒）。单因素回归分析显示，IBW百分比与最大和次最大有氧能力指标相关：与VO₂峰值相比，R = 0.53（p < 0.01）；与MRT相比，R = -0.77（p < 0.001）。使用逐步回归分析，MRT与IBW百分比（R² = -0.70）（p < 0.01）以及与PaO₂（p < 0.05）相关。
体重减轻对COPD患者的肌肉有氧能力有独立的负面影响：这种影响可能解释了具有相当通气限制的患者之间运动耐力的差异。
