Neuroscience Research Australia and University of New South Wales, Sydney, Australia.
Neuroscience Research Australia and University of New South Wales, Sydney, Australia; Platypus Technical Consultants Pty Ltd, Canberra, Australia.
Respir Physiol Neurobiol. 2020 Mar;274:103353. doi: 10.1016/j.resp.2019.103353. Epub 2019 Nov 21.
How the involuntary (bulbospinal) and voluntary (corticospinal) pathways interact in respiratory muscle control is not established. To determine the role of excitatory corticobulbar pathways in humans, studies typically compare electromyographic activity (EMG) or evoked responses in respiratory muscles during hypercapnic and voluntary tasks. Although ventilation is matched between tasks by having participants track signals of ventilation, these tasks may not result in matched respiratory muscle activity. The aim of this study was to describe respiratory muscle activity and ribcage and abdominal excursions during two different voluntary conditions, compared to hypercapnic hyperventilation. Ventilation was matched in the voluntary conditions via (i) a simple target of lung volume ('volume tracking') or (ii) targets of both ribcage and abdominal excursions, adjusted to end-expiratory lung volume in hypercapnic hyperventilation ('bands tracking'). Compared to hypercapnic hyperventilation, respiratory parameters such as tidal volume were similar, but the ratio of ribcage to abdominal excursion was higher for both voluntary tasks. Inspiratory scalene and parasternal intercostal muscle activity was higher in volume tracking, but diaphragm and abdominal muscle activity showed little to no change. There were no differences in muscle activity in bands tracking for any muscle, compared to hypercapnic hyperventilation. An elevated ratio of ribcage to abdominal excursion in the bands tracking task indicates that participants could not accurately match the targets in this condition. Inspiratory muscle activity is altered in some muscles in some voluntary tasks, compared to hypercapnia. Therefore, differences in muscle activity should be considered in interpretation of studies that use these protocols to investigate respiratory muscle control.
不随意（脊髓）和随意（皮质脊髓）通路如何相互作用于呼吸肌控制尚不清楚。为了确定兴奋性皮质延髓束在人类中的作用，研究通常比较在高碳酸血症和自主任务期间呼吸肌的肌电图活动（EMG）或诱发反应。尽管通过让参与者跟踪通气信号来使任务之间的通气相匹配，但这些任务可能不会导致呼吸肌活动相匹配。本研究的目的是描述两种不同自主条件下（与高碳酸血症过度通气相比）呼吸肌活动和肋骨和腹部运动。在自主条件下，通过（i）肺容积的简单目标（“容积跟踪”）或（ii）肋骨和腹部运动的目标，并调整为高碳酸血症过度通气中的呼气末肺容积（“带跟踪”）来匹配通气。与高碳酸血症过度通气相比，潮气量等呼吸参数相似，但两种自主任务的肋骨和腹部运动的比率都更高。在容积跟踪中，斜角肌和胸骨旁肋间肌的吸气肌活动更高，但膈肌和腹肌活动几乎没有变化。与高碳酸血症过度通气相比，带跟踪中任何肌肉的肌肉活动均无差异。在带跟踪任务中，肋骨和腹部运动的比率升高表明参与者无法准确匹配该条件下的目标。与高碳酸血症相比，一些自主任务中的一些吸气肌的活动发生改变。因此，在解释使用这些方案来研究呼吸肌控制的研究时，应考虑肌肉活动的差异。
