Section of Pulmonary and Critical Care Medicine, Dartmouth Medical School, Dartmouth-Hitchcock Medical Center, Lebanon, NH.
Section of Pulmonary and Critical Care Medicine, Dartmouth Medical School, Dartmouth-Hitchcock Medical Center, Lebanon, NH.
Chest. 2011 Aug;140(2):351-358. doi: 10.1378/chest.10-2415. Epub 2011 Jan 27.
Patients with COPD exhibit greater oxyhemoglobin desaturation during walking than with cycling. The purpose of this investigation was to investigate differences in ventilatory responses and gas exchange as proposed mechanisms for this observation.
Arterial blood gas and lactate levels were measured in 12 patients with COPD (aged 68 ± 6 years) during incremental treadmill and cycle exercise. The primary outcome to assess the ventilatory response to exercise was Pao₂. The primary outcome to assess impairment in exercise gas exchange was the difference between partial pressures of alveolar and arterial oxygen (Pao₂ - Pao₂).
Pao₂ in patients was significantly lower at peak exercise for treadmill walking (51.4 ± 6.8 mm Hg) compared with cycling (60.4 ± 10.7 mm Hg) (P = .002). The initial increase in Pao₂ with cycling occurred prior to the onset of the anaerobic threshold. At peak exercise, Pao₂ was significantly higher with cycling compared with walking (P = .004). The anaerobic threshold occurred at a lower oxygen consumption during cycling than walking (P = .001), and peak lactate levels were higher with cycling (P = .019). With progressive exercise, Pao₂ - Pao₂ increased similarly during treadmill and cycle exercise.
The higher Pao₂ during cycling minimized the magnitude of oxyhemoglobin desaturation compared with walking. The enhanced respiratory stimulation during cycling appears due to an initial neurogenic process, possibly originating in receptors of exercising muscles, and a subsequent earlier onset of anaerobic metabolism with higher lactate levels during cycling.
与骑自行车相比，COPD 患者在行走时会出现更大的氧合血红蛋白饱和度下降。本研究旨在探究通气反应和气体交换的差异，这些差异可能是导致这一观察结果的机制。
12 例 COPD 患者（年龄 68±6 岁）进行递增跑步机和自行车运动时，测量动脉血气和乳酸水平。评估运动时通气反应的主要结果指标是 PaO₂。评估运动时气体交换受损的主要结果指标是肺泡和动脉氧分压之间的差异（PaO₂-PaO₂）。
与骑自行车相比，患者在跑步机行走时的峰值运动时 PaO₂显著降低（51.4±6.8mmHg）（P=0.002）。骑自行车时 PaO₂的初始增加发生在无氧阈之前。在峰值运动时，与步行相比，骑自行车时 PaO₂显著升高（P=0.004）。与步行相比，骑自行车时无氧阈的耗氧量更低（P=0.001），峰值乳酸水平也更高（P=0.019）。随着运动的进行，在跑步机和自行车运动时，PaO₂-PaO₂的增加相似。
与步行相比，骑自行车时较高的 PaO₂最大限度地减少了氧合血红蛋白饱和度的降低程度。与步行相比，在骑自行车时呼吸刺激增强可能是由于初始的神经源性过程，可能起源于运动肌肉的受体，以及随后的无氧代谢更早开始，同时产生更高的乳酸水平。
