Department of Physical Medicine and Rehabilitation, Case Western Reserve University, MetroHealth Medical Center , Cleveland, Ohio.
Department of Research, Case Western Reserve University, MetroHealth Medical Center , Cleveland, Ohio.
J Appl Physiol (1985). 2019 Jul 1;127(1):98-102. doi: 10.1152/japplphysiol.00006.2019. Epub 2019 May 16.
High-frequency spinal cord stimulation (HF-SCS) applied at the T2 spinal level results in physiologic activation of the inspiratory muscles in C2 spinal-sectioned dogs. Although the bulbo-spinal fibers were cut, they likely survived the duration of acute experiments, and inspiratory muscle activation may have involved stimulation of these fibers. In two anesthetized, C2 paralyzed, intubated, and mechanically ventilated dogs, HF-SCS (300 Hz) was applied at the T2 level. The effectiveness of HF-SCS in generating inspired volume (V) and negative airway pressures (P) was evaluated over a period of 5 days during which time the bulbo-spinal fibers would have degenerated. Because the effectiveness of HF-SCS may be adversely affected by deterioration of these fibers and/or the condition of the animal, low-frequency (50 Hz) SCS (LF-SCS) was also performed and served as a control. All vital signs, oxygen saturation, and end-tidal Pco remained stable over the 5-day period. V and P also remained stable over the study period. For example, mean V and P were 771 ± 25 ml and 64 ± 1 cmHO with HF-SCS (3 mA) during the initial and 674 ± 59 ml and 63 ± 5 cmHO on the final day. Comparable values during LF-SCS (8 mA) were 467 ± 12 ml and 48 ± 1 cmHO during the initial and 397 ± 20 ml and 42 ± 2 cmHO on the final day. Because V and P in response to HF-SCS remained stable over a 5-day period following which the bulbo-spinal fibers would have degenerated, the mechanism of HF-SCS does not depend upon the viability of these tracts. HF-SCS therefore may be a useful method to restore ventilation in chronic ventilator dependent tetraplegics. This study indicates that the respiratory responses to high-frequency spinal cord stimulation applied at the T2 level results in activation of the inspiratory motoneuron pools via interneuronal circuits and/or the inspiratory motoneurons directly and does not depend upon activation of long descending inspiratory bulbo-spinal fibers. This method therefore, may provide an alternative method to restore ventilation in ventilator dependent spinal cord injured patients.
高频脊髓刺激（HF-SCS）施加于 T2 脊髓水平会导致 C2 脊髓节段切断犬的吸气肌产生生理性激活。尽管球脊髓纤维被切断，但它们可能在急性实验的持续时间内存活，并且吸气肌激活可能涉及对这些纤维的刺激。在两只麻醉、C2 瘫痪、插管和机械通气的狗中，在 T2 水平施加高频脊髓刺激（300Hz）。在球脊髓纤维退化的 5 天期间，评估 HF-SCS 在产生吸气量（V）和负气道压力（P）方面的有效性。由于 HF-SCS 的有效性可能会受到这些纤维的恶化和/或动物状况的不利影响，因此还进行了低频（50Hz）SCS（LF-SCS），并作为对照。在 5 天的研究期间，所有生命体征、氧饱和度和呼气末 Pco2 保持稳定。V 和 P 在研究期间也保持稳定。例如，在 HF-SCS（3mA）下，初始时平均 V 和 P 分别为 771±25ml 和 64±1cmHO，最后一天分别为 674±59ml 和 63±5cmHO。在 LF-SCS（8mA）下，初始时的可比值分别为 467±12ml 和 48±1cmHO，最后一天分别为 397±20ml 和 42±2cmHO。由于 HF-SCS 引起的 V 和 P 在球脊髓纤维退化后 5 天内保持稳定，因此 HF-SCS 的机制不依赖于这些束的活力。因此，HF-SCS 可能是一种恢复慢性呼吸机依赖四肢瘫痪患者通气的有用方法。本研究表明，T2 水平施加的高频脊髓刺激引起吸气运动神经元池的激活通过中间神经元回路和/或吸气运动神经元直接，而不依赖于长下行吸气球脊髓纤维的激活。因此，这种方法可能为恢复呼吸机依赖的脊髓损伤患者的通气提供替代方法。
