Kurotobi T, Sato H, Yokoyama H, Li D, Koretsune Y, Ohnishi Y, Karita M, Takeda H, Kuzuya T, Hori M
First Department of Medicine, Osaka University School of Medicine, Japan.
J Card Fail. 1997 Sep;3(3):181-8. doi: 10.1016/s1071-9164(97)90014-2.
Although the work of the respiratory muscles is markedly increased during exercise in patients with chronic heart failure, the role of this abnormality in exercise intolerance is still controversial. This issue may be clarified directly by dead space challenge, as this technique increases minute ventilation. Therefore, in this study, the effects of an external dead space on exercise ventilation, gas exchange data, and exercise capacity in patients with chronic heart failure were examined.
Dead space challenge was performed by adding an external dead space to the airway in 20 patients with chronic heart failure and 10 normal subjects. Two hours after completion of the control maximal bicycle exercise, the second exercise was performed under application of an external dead space equivalent to 10% of peak tidal volume. Respiratory gas exchange data were collected during exercise. Aerobic exercise capacity was assessed from the exercise time and the time to anaerobic threshold. The sensation of exertional dyspnea was assessed using Borg's rating scale. As compared with data during the control exercise, minute ventilation was increased by approximately 25% with the external dead space throughout exercise in both groups. A parallel 20% increase in systemic oxygen uptake was observed in the heart failure group, likely reflecting an increase in respiratory muscle work. This response was not observed in the normal group. Despite an additional increase in respiratory muscle work, neither aerobic exercise capacity nor exertional dyspnea was exacerbated in the heart failure group by the external dead space.
Dead space challenge appears to be a unique technique that characteristically increases the work of respiratory muscles during exercise in patients with chronic heart failure. By use of this technique, it was demonstrated that an increase in respiratory muscle work is not important in reducing exercise capacity of patients with chronic heart failure.
尽管慢性心力衰竭患者在运动期间呼吸肌的工作量显著增加，但这种异常在运动不耐受中的作用仍存在争议。死腔激发试验可直接阐明这一问题，因为该技术可增加分钟通气量。因此，在本研究中，我们检测了外部死腔对慢性心力衰竭患者运动通气、气体交换数据和运动能力的影响。
对20例慢性心力衰竭患者和10名正常受试者通过在气道中添加外部死腔进行死腔激发试验。在完成对照最大负荷自行车运动两小时后，进行第二次运动，此时应用相当于潮气量峰值10%的外部死腔。运动期间收集呼吸气体交换数据。根据运动时间和无氧阈时间评估有氧运动能力。使用Borg评分量表评估运动性呼吸困难的感觉。与对照运动期间的数据相比，两组在整个运动过程中使用外部死腔时分钟通气量均增加了约25%。心力衰竭组全身氧摄取量平行增加了20%，这可能反映了呼吸肌工作量的增加。正常组未观察到这种反应。尽管呼吸肌工作量进一步增加，但心力衰竭组的有氧运动能力和运动性呼吸困难均未因外部死腔而加重。
死腔激发试验似乎是一种独特的技术，其特点是在慢性心力衰竭患者运动期间增加呼吸肌的工作量。通过使用该技术，证明呼吸肌工作量的增加对降低慢性心力衰竭患者的运动能力并不重要。
