National Heart and Lung Institute, Imperial College, Royal Brompton Hospital, Fulham Rd, London SW3 6NP, UK.
Respir Res. 2010 Feb 4;11(1):15. doi: 10.1186/1465-9921-11-15.
In patients with chronic obstructive pulmonary disease, a restriction on maximum ventilatory capacity contributes to exercise limitation. It has been demonstrated that the diaphragm in COPD is relatively protected from fatigue during exercise. Because of expiratory flow limitation the abdominal muscles are activated early during exercise in COPD. This adds significantly to the work of breathing and may therefore contribute to exercise limitation. In healthy subjects, prior expiratory muscle fatigue has been shown itself to contribute to the development of quadriceps fatigue. It is not known whether fatigue of the abdominal muscles occurs during exercise in COPD.
Twitch gastric pressure (TwT10Pga), elicited by magnetic stimulation over the 10th thoracic vertebra and twitch transdiaphragmatic pressure (TwPdi), elicited by bilateral anterolateral magnetic phrenic nerve stimulation were measured before and after symptom-limited, incremental cycle ergometry in patients with COPD.
Twenty-three COPD patients, with a mean (SD) FEV1 40.8(23.1)% predicted, achieved a mean peak workload of 53.5(15.9) W. Following exercise, TwT10Pga fell from 51.3(27.1) cmH2O to 47.4(25.2) cmH2O (p = 0.011). TwPdi did not change significantly; pre 17.0(6.4) cmH2O post 17.5(5.9) cmH2O (p = 0.7). Fatiguers, defined as having a fall TwT10Pga > or = 10% had significantly worse lung gas transfer, but did not differ in other exercise parameters.
In patients with COPD, abdominal muscle but not diaphragm fatigue develops following symptom limited incremental cycle ergometry. Further work is needed to establish whether abdominal muscle fatigue is relevant to exercise limitation in COPD, perhaps indirectly through an effect on quadriceps fatigability.
在慢性阻塞性肺疾病（COPD）患者中，最大通气能力的受限导致运动受限。已经证明，COPD 患者的膈肌在运动中相对不易疲劳。由于呼气流量受限，COPD 患者在运动早期即开始动用腹部肌肉。这显著增加了呼吸功，可能因此导致运动受限。在健康受试者中，先前的呼气肌疲劳已被证明会导致股四头肌疲劳的发展。尚不清楚 COPD 患者在运动中是否会发生腹部肌肉疲劳。
通过第 10 胸椎磁刺激引出的胃 twitch 压（TwT10Pga）和双侧前外侧膈神经磁刺激引出的 twitch 膈压（TwPdi），在 COPD 患者症状限制递增式踏车运动前后进行测量。
23 例 COPD 患者，平均（标准差）FEV1 为预计值的 40.8（23.1）%，达到平均峰值工作负荷 53.5（15.9）W。运动后，TwT10Pga 从 51.3（27.1）cmH2O 降至 47.4（25.2）cmH2O（p=0.011）。TwPdi 无显著变化；运动前 17.0（6.4）cmH2O，运动后 17.5（5.9）cmH2O（p=0.7）。定义为 TwT10Pga 下降≥10%的疲劳者，其肺气体交换明显更差，但在其他运动参数上无差异。
在症状限制递增式踏车运动后，COPD 患者出现腹部肌肉但不是膈肌疲劳。需要进一步的工作来确定腹部肌肉疲劳是否与 COPD 患者的运动受限相关，可能是通过对股四头肌疲劳性的间接影响。
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