Neuroscience Research Australia (NeuRA), Randwick, NSW, Australia.
University of Melbourne, Melbourne, Australia.
J Physiol. 2018 Jul;596(14):2853-2864. doi: 10.1113/JP275222. Epub 2018 Apr 25.
Protective reflexes in the throat area (upper airway) are crucial for breathing. Impairment of these reflexes can cause breathing problems during sleep such as obstructive sleep apnoea (OSA). OSA is very common in people with spinal cord injury for unknown reasons. This study shows major changes in protective reflexes that serve to keep the upper airway open in response to suction pressures in people with tetraplegia and OSA. These results help us understand why OSA is so common in people with tetraplegia and provide new insight into how protective upper airway reflexes work more broadly.
More than 60% of people with tetraplegia have obstructive sleep apnoea (OSA). However, the specific causes are unknown. Genioglossus, the largest upper-airway dilator muscle, is important in maintaining upper-airway patency. Impaired genioglossus muscle function following spinal cord injury may contribute to OSA. This study aimed to determine if genioglossus reflex responses to negative upper-airway pressure are altered in people with OSA and tetraplegia compared to non-neurologically impaired able-bodied individuals with OSA. Genioglossus reflex responses measured via intramuscular electrodes to ∼60 brief (250 ms) pulses of negative upper-airway pressure (∼-15 cmH O at the mask) were compared between 13 participants (2 females) with tetraplegia plus OSA and 9 able-bodied controls (2 females) matched for age and OSA severity. The initial short-latency excitatory reflex response was absent in 6/13 people with tetraplegia and 1/9 controls. Genioglossus reflex inhibition in the absence of excitation was observed in three people with tetraplegia and none of the controls. When the excitatory response was present, it was significantly delayed in the tetraplegia group compared to able-bodied controls: excitation onset latency (mean ± SD) was 32 ± 16 vs. 18 ± 9 ms, P = 0.045; peak excitation latency was 48 ± 17 vs. 33 ± 8 ms, P = 0.038. However, when present, amplitude of the excitation response was not different between groups, 195 ± 26 vs. 219 ± 98% at baseline, P = 0.55. There are major differences in genioglossus reflex morphology and timing in response to rapid changes in airway pressure in people with tetraplegia and OSA. Altered genioglossus function may contribute to the increased risk of OSA in people with tetraplegia. The precise mechanisms mediating these differences are unknown.
喉咙区域（上呼吸道）的保护性反射对于呼吸至关重要。这些反射的功能障碍可导致睡眠期间出现呼吸问题，如阻塞性睡眠呼吸暂停（OSA）。脊髓损伤患者 OSA 的发病率极高，但具体原因尚不清楚。本研究表明，在患有四肢瘫痪和 OSA 的人群中，对上呼吸道起保护作用的反射会发生重大变化，以响应负压吸嘴的吸力。这些结果有助于我们了解为什么脊髓损伤患者 OSA 的发病率如此之高，并为更广泛的上呼吸道保护反射的工作机制提供了新的见解。
超过 60%的四肢瘫痪患者患有阻塞性睡眠呼吸暂停（OSA）。然而，其具体病因尚不清楚。颏舌肌是最大的上呼吸道扩张肌，对上气道通畅性的维持非常重要。脊髓损伤后颏舌肌功能障碍可能导致 OSA。本研究旨在确定与非神经损伤的 OSA 健康对照组相比，患有 OSA 的四肢瘫痪患者对上气道负压的颏舌肌反射反应是否存在差异。通过肌内电极测量了 13 名（2 名女性）四肢瘫痪合并 OSA 患者（60 次短暂（250ms）负压脉冲，面罩压力约为-15cmH2O）和 9 名年龄和 OSA 严重程度匹配的非神经损伤的 OSA 健康对照组（2 名女性）的颏舌肌反射反应。在 13 名四肢瘫痪患者中，有 6 名患者的初始短潜伏期兴奋性反射反应缺失，而对照组 9 名中仅有 1 名缺失。在 3 名四肢瘫痪患者中观察到无兴奋的颏舌肌反射抑制，而对照组中无此现象。在存在兴奋性反应的情况下，与对照组相比，四肢瘫痪组的兴奋起始潜伏期明显延迟：兴奋起始潜伏期（均值±标准差）分别为 32±16ms 和 18±9ms，P=0.045；兴奋峰值潜伏期分别为 48±17ms 和 33±8ms，P=0.038。然而，两组之间的兴奋反应幅度没有差异，基础值分别为 195±26%和 219±98%，P=0.55。在患有四肢瘫痪和 OSA 的人群中，对气道压力的快速变化，颏舌肌反射的形态和时程存在明显差异。颏舌肌功能的改变可能会增加四肢瘫痪患者发生 OSA 的风险。介导这些差异的确切机制尚不清楚。
