Dragomir Andrei, Akay Yasemin, Curran Aidan K, Akay Metin
Harrington Department of Bioengineering, Ira A. Fulton School of Engineering Arizona State University, Tempe, AZ 85287, USA.
J Neuroeng Rehabil. 2008 Jun 20;5:17. doi: 10.1186/1743-0003-5-17.
The laryngeal chemoreflex exists in infants as a primary sensory mechanism for defending the airway from the aspiration of liquids. Previous studies have hypothesized that prolonged apnea associated with this reflex may be life threatening and might be a cause of sudden infant death syndrome.
In this study we quantified the output of the respiratory neural network, the diaphragm EMG signal, during the laryngeal chemoreflex and eupnea in early postnatal (3-10 days) piglets. We tested the hypothesis that diaphragm EMG activity corresponding to reflex-related events involved in clearance (restorative) mechanisms such as cough and swallow exhibit lower complexity, suggesting that a synchronized homogeneous group of neurons in the central respiratory network are active during these events. Nonlinear dynamic analysis was performed using the approximate entropy to asses the complexity of respiratory patterns.
Diaphragm EMG, genioglossal activity EMG, as well as other physiological signals (tracheal pressure, blood pressure and respiratory volume) were recorded from 5 unanesthetized chronically instrumented intact piglets. Approximate entropy values of the EMG during cough and swallow were found significantly (p < 0.05 and p < 0.01 respectively) lower than those of eupneic EMG.
Reduced complexity values of the respiratory neural network output corresponding to coughs and swallows suggest synchronous neural activity of a homogeneous group of neurons. The higher complexity values exhibited by eupneic respiratory activity are the result of a more random behaviour, which is the outcome of the integrated action of several groups of neurons involved in the respiratory neural network.
喉化学反射作为一种主要的感觉机制存在于婴儿中，用于保护气道免受液体误吸。先前的研究推测，与这种反射相关的长时间呼吸暂停可能危及生命，并且可能是婴儿猝死综合征的一个原因。
在本研究中，我们对出生后早期（3 - 10天）仔猪在喉化学反射和平静呼吸期间呼吸神经网络的输出即膈肌肌电图信号进行了量化。我们检验了这样一个假设，即与咳嗽和吞咽等清除（恢复性）机制中涉及的反射相关事件相对应的膈肌肌电图活动表现出较低的复杂性，这表明在这些事件期间中枢呼吸网络中一组同步的同质神经元是活跃的。使用近似熵进行非线性动力学分析，以评估呼吸模式的复杂性。
从5只未麻醉、长期植入仪器的完整仔猪记录了膈肌肌电图、颏舌肌活动肌电图以及其他生理信号（气管压力、血压和呼吸量）。发现咳嗽和吞咽期间肌电图的近似熵值显著低于平静呼吸肌电图（分别为p < 0.05和p < 0.01）。
与咳嗽和吞咽相对应的呼吸神经网络输出的复杂性值降低表明一组同质神经元的同步神经活动。平静呼吸活动表现出的较高复杂性值是更随机行为的结果，这是参与呼吸神经网络的几组神经元综合作用的结果。
