Department of Critical Care Medicine and Pulmonary Services, Evangelismos Hospital, M. Simou and G.P. Livanos Laboratories, National and Kapodistrian University of Athens, Athens, Greece.
J Appl Physiol (1985). 2012 Oct;113(7):1012-23. doi: 10.1152/japplphysiol.00481.2012. Epub 2012 Aug 9.
Some reports suggest that heliox breathing during exercise may improve peripheral muscle oxygen availability in patients with chronic obstructive pulmonary disease (COPD). Besides COPD patients who dynamically hyperinflate during exercise (hyperinflators), there are patients who do not hyperinflate (non-hyperinflators). As heliox breathing may differently affect cardiac output in hyperinflators (by increasing preload and decreasing afterload of both ventricles) and non-hyperinflators (by increasing venous return) during exercise, it was reasoned that heliox administration would improve peripheral muscle oxygen delivery possibly by different mechanisms in those two COPD categories. Chest wall volume and respiratory muscle activity were determined during constant-load exercise at 75% peak capacity to exhaustion, while breathing room air or normoxic heliox in 17 COPD patients: 9 hyperinflators (forced expiratory volume in 1 s = 39 ± 5% predicted), and 8 non-hyperinflators (forced expiratory volume in 1 s = 48 ± 5% predicted). Quadriceps muscle blood flow was measured by near-infrared spectroscopy using indocyanine green dye. Hyperinflators and non-hyperinflators demonstrated comparable improvements in endurance time during heliox (231 ± 23 and 257 ± 28 s, respectively). At exhaustion in room air, expiratory muscle activity (expressed by peak-expiratory gastric pressure) was lower in hyperinflators than in non-hyperinflators. In hyperinflators, heliox reduced end-expiratory chest wall volume and diaphragmatic activity, and increased arterial oxygen content (by 17.8 ± 2.5 ml/l), whereas, in non-hyperinflators, heliox reduced peak-expiratory gastric pressure and increased systemic vascular conductance (by 11.0 ± 2.8 ml·min(-1)·mmHg(-1)). Quadriceps muscle blood flow and oxygen delivery significantly improved during heliox compared with room air by a comparable magnitude (in hyperinflators by 6.1 ± 1.3 ml·min(-1)·100 g(-1) and 1.3 ± 0.3 ml O(2)·min(-1)·100 g(-1), and in non-hyperinflators by 7.2 ± 1.6 ml·min(-1)·100 g(-1) and 1.6 ± 0.3 ml O(2)·min(-1)·100 g(-1), respectively). Despite similar increase in locomotor muscle oxygen delivery with heliox in both groups, the mechanisms of such improvements were different: 1) in hyperinflators, heliox increased arterial oxygen content and quadriceps blood flow at similar cardiac output, whereas 2) in non-hyperinflators, heliox improved central hemodynamics and increased systemic vascular conductance and quadriceps blood flow at similar arterial oxygen content.
一些报告表明，在慢性阻塞性肺疾病（COPD）患者运动时使用氦氧混合气呼吸可能会改善外周肌肉的氧气供应。除了在运动时动态过度充气的 COPD 患者（过度充气者）外，还有不发生过度充气的患者（非过度充气者）。由于氦氧混合气呼吸可能通过不同的机制在过度充气者（通过增加心室前负荷和后负荷）和非过度充气者（通过增加静脉回流）中在运动期间影响心输出量，因此有人认为氦氧混合气呼吸可能通过不同的机制在这两种 COPD 类别中改善外周肌肉的氧气输送。在 17 名 COPD 患者中，通过恒定负荷运动（75%的峰值容量直至衰竭）确定胸壁容积和呼吸肌活动，同时在呼吸室内空气或高氧氦氧混合气时：9 名过度充气者（第 1 秒用力呼气量 = 39 ± 5%预计值）和 8 名非过度充气者（第 1 秒用力呼气量 = 48 ± 5%预计值）。使用吲哚菁绿染料通过近红外光谱法测量股四头肌血流。在氦氧混合气中，过度充气者和非过度充气者的耐力时间均有类似的改善（分别为 231 ± 23 和 257 ± 28 秒）。在室内空气下衰竭时，过度充气者的呼气肌活动（以峰呼气胃内压表示）低于非过度充气者。在过度充气者中，氦氧混合气降低了呼气末胸壁容积和膈肌活动，并增加了动脉血氧含量（增加 17.8 ± 2.5 ml/l），而在非过度充气者中，氦氧混合气降低了峰呼气胃内压并增加了全身血管传导率（增加 11.0 ± 2.8 ml·min^-1·mmHg^-1）。与室内空气相比，氦氧混合气显著改善了股四头肌血流和氧气输送，改善程度相当（在过度充气者中，股四头肌血流增加 6.1 ± 1.3 ml·min^-1·100 g^-1，氧气输送增加 1.3 ± 0.3 ml O2·min^-1·100 g^-1，而非过度充气者中，股四头肌血流增加 7.2 ± 1.6 ml·min^-1·100 g^-1，氧气输送增加 1.6 ± 0.3 ml O2·min^-1·100 g^-1）。尽管两组患者的运动肌肉氧气输送均有类似的增加，但改善的机制却不同：1）在过度充气者中，氦氧混合气增加了动脉血氧含量和股四头肌血流，而心输出量相似，而 2）在非过度充气者中，氦氧混合气改善了中枢血液动力学，并增加了全身血管传导率和股四头肌血流，而动脉血氧含量相似。
