Respiratory and locomotor muscle blood flow regulation during physiological stress

呼吸肌已被证明在需要高水平肌肉工作(例如，高强度运动)的任务中会出现疲劳。呼吸肌疲劳被认为是一种重要的反射反应，减少了腿部肌肉的血流量。这种血流量的减少被称为“偷窃现象”，即假设呼吸肌从腿部肌肉中窃取血液流动，导致腿部肌肉疲劳程度增加，腿部不适加剧，最终降低运动能力。支持这一现象的一个主要挑战是无法测量人类呼吸肌血流量(RMBF)，这在很大程度上是由于呼吸肌的复杂解剖排列和血管网络。然而，我们最近克服了这些挑战，成为第一批使用近红外光谱技术和光吸收示踪剂吲哚青绿成功测量人体RMBF的研究人员。测量RMBF的能力将使我们能够解决与运动肌肉和呼吸肌之间的血流竞争相关的几个悬而未决的问题，并将为人类呼吸肌疲劳的机制提供重要的洞察。因此，拟议研究计划的长期目标是系统地研究在生理应激增加的情况下人类呼吸肌功能和血流分布之间的复杂关系。具体地说，这项研究将在实验中操纵呼吸的工作，以检查呼吸肌疲劳如何影响呼吸肌招募模式、神经呼吸驱动以及休息和运动时的血流分布。从这项研究中获得的新见解将增强我们对健康人类心肺相互作用和运动限制的基本理解。这项工作将为未来的研究奠定基础，这些研究旨在了解呼吸肌功能或血流可能受到影响的几种情况的病理生理学，例如慢性心肺疾病患者或正在接受机械呼吸的患者。

The respiratory muscles have been shown to develop fatigue during tasks that require high levels of muscular work (e.g., intense exercise). Respiratory muscle fatigue is thought to causes an important reflex response that reduces blood flow to the leg muscles. This reduction in blood flow has been termed the "steal phenomenon" whereby the respiratory muscles are hypothesized to steal blood flow from the leg muscles leading to an increased level of leg muscle fatigue, increased perceived leg discomfort and ultimately, reduced exercise performance. A major challenge in supporting this phenomenon has been the inability to measure respiratory muscle blood flow (RMBF) in humans, due in large part, to the complex anatomical arrangement and vascular network of the respiratory muscles. However, we recently overcame these challenges and became the first researchers to successfully measure RMBF in humans using near-infrared spectroscopy technology and the light absorbing tracer indocyanine green. The ability to measure RMBF will allow us to address several unanswered questions related to blood flow competition between the locomotor and respiratory muscles and will provide significant insight into the mechanisms of respiratory muscle fatigue in humans. Accordingly, the long-term goal of the proposed research program is to systematically examine the complex relationship between respiratory muscle function and blood flow distribution in humans under situations of increased physiological stress. Specifically, this research will experimentally manipulate the work of breathing to examine how respiratory muscle fatigue affects respiratory muscle recruitment patterns, neural respiratory drive, and blood flow distribution at rest and during exercise. The novel insight gained from this research will enhance our fundamental understanding of cardio-respiratory interactions and exercise limitations in healthy humans. This work will act as a foundation for future studies aimed at understanding the pathophysiology of several conditions where respiratory muscle function or blood flow may be compromised such as in patients with chronic cardio-respiratory disease or in patients that are being mechanically ventilated.