Laghi F, Harrison M J, Tobin M J
Division of Pulmonary and Critical Care Medicine, Edward Hines, Jr. Veterans Affairs Hospital, Hines, Illinois 60141, USA.
J Appl Physiol (1985). 1996 May;80(5):1731-42. doi: 10.1152/jappl.1996.80.5.1731.
Unlike the standard electrical approach, cervical magnetic stimulation of the phrenic nerves is less painful and achieves a constant degree of diaphragmatic recruitment, features that should enhance its applicability in a clinical setting. An unexplained phenomenon is the greater transdiaphragmatic twitch pressure (Pditw) with magnetic vs. electrical stimulation. We hypothesized that this greater Pditw is due to coactivation of extradiaphragmatic muscles. Because impedance to rib cage expansion is increased at high lung volumes and efficiency of extradiaphragmatic muscles is less than that of the diaphragm, we reasoned that the difference between electrical Pditw and magnetic Pditw would be less evident at high volumes than at end-expiratory lung volume. In human volunteers, magnetic Pditw and electrical Pditw were 37.7 +/- 1.9 (SE) and 32.3 +/- 2.2 cmH2O, respectively, at end-expiratory lung volume (P < 0.005) and 24.0 +/- 2.9 and 27.2 +/- 2.8 cmH2O, respectively, at one-half inspiratory capacity (not significant); at total lung capacity, magnetic Pditw was less than electrical Pditw (10.6 +/- 0.8 and 16.2 +/- 2.9 cmH2O, respectively; P < 0.05). Magnetic stimulation caused significant extradiaphragmatic muscle depolarization and rib cage expansion, whereas electrical stimulation caused virtually no extradiaphragmatic muscle depolarization and rib cage deflation. Despite these differences, the induction of respiratory muscle fatigue produced reductions in both electrical and magnetic Pditw values (P < 0.01), which were of similar magnitude and closely correlated (r = 0.96). In conclusion, magnetic stimulation recruits both extradiaphragmatic and diaphragmatic muscles, and it is equally as effective as electrical stimulation in detecting diaphragmatic fatigue.
与标准电刺激方法不同，膈神经的颈部磁刺激疼痛较轻，且能实现恒定程度的膈肌募集，这些特性应会提高其在临床环境中的适用性。一个无法解释的现象是，与电刺激相比，磁刺激时跨膈抽搐压力（Pditw）更大。我们推测，这种更大的Pditw是由于膈外肌肉的共同激活所致。由于在高肺容积时胸廓扩张的阻力增加，且膈外肌肉的效率低于膈肌，我们推断，在高容积时电刺激Pditw与磁刺激Pditw之间的差异比在呼气末肺容积时不那么明显。在人类志愿者中，呼气末肺容积时磁刺激Pditw和电刺激Pditw分别为37.7±1.9（标准误）和32.3±2.2 cmH2O（P<0.005），在吸气容量一半时分别为24.0±2.9和27.2±2.8 cmH2O（无显著差异）；在肺总量时，磁刺激Pditw小于电刺激Pditw（分别为10.6±0.8和16.2±2.9 cmH2O；P<0.05）。磁刺激导致膈外肌肉明显去极化和胸廓扩张，而电刺激几乎未导致膈外肌肉去极化和胸廓缩小。尽管存在这些差异，但呼吸肌疲劳的诱发使电刺激和磁刺激的Pditw值均降低（P<0.01），降低幅度相似且密切相关（r=0.96）。总之，磁刺激可募集膈外肌肉和膈肌，并且在检测膈肌疲劳方面与电刺激同样有效。
