Oliven A, Odeh M
Dept. of Medicine B, Bnai-Zion Medical Center, Technion, Haifa 31048, Israel.
J Appl Physiol (1985). 2006 Sep;101(3):745-51. doi: 10.1152/japplphysiol.01462.2005. Epub 2006 May 4.
Positional changes of anatomic structures surrounding the upper airway are known to affect pharyngeal mechanics and collapsibility. We hypothesized that these alterations also affect the ability of the upper airway dilator muscles to enlarge the pharynx by altering their ability to shorten when activated. Using sonomicrometry, we evaluated in seven anesthetized dogs the effects of changes in tracheal and head position on the length of the genioglossus (GG) and the geniohyoid (GH) and the effects of these positional changes on the magnitude of shortening of the two muscles in response to electro- (ES) and chemostimulation (CS). Caudal traction of the trachea lengthened the GG and GH in all dogs, whereas cranial displacement of the trachea and flexion of the head to a vertical position shortened the muscles. Compared with the magnitude of ES-induced shortening in the neutral position, ES-induced shortening of the GG was 144.7 +/- 14.6, 49.3 +/- 4.3, and 33.5 +/- 11.6% during caudal and cranial displacement of the trachea and during head flexion, respectively. Similar effects of the positional changes were found for the GH, as well as for both muscles during respiratory stimulation with P(CO2) of 90 Torr at the end of CO(2) rebreathing, although inspiratory muscle shortening during CS reached only one-quarter to one-third of the magnitude observed during ES. We conclude that positional alterations of anatomic structures in the neck have a dramatic effect on the magnitude of shortening of the activated GG and GH, which may reduce substantially their ability to protect pharyngeal patency.
已知上呼吸道周围解剖结构的位置变化会影响咽部力学和可塌陷性。我们推测这些改变也会影响上呼吸道扩张肌通过改变其激活时缩短的能力来扩大咽部的能力。使用超声测量法，我们评估了七只麻醉犬中气管和头部位置的变化对颏舌肌（GG）和颏舌骨肌（GH）长度的影响，以及这些位置变化对这两块肌肉在电刺激（ES）和化学刺激（CS）时缩短幅度的影响。在所有犬中，气管的尾端牵引使GG和GH延长，而气管的头端移位和头部向垂直位置弯曲则使肌肉缩短。与中立位置时ES诱导的缩短幅度相比，在气管尾端和头端移位以及头部弯曲时，ES诱导的GG缩短分别为144.7±14.6%、49.3±4.3%和33.5±11.6%。对于GH以及在二氧化碳再呼吸结束时P(CO2)为90 Torr的呼吸刺激期间两块肌肉，也发现了类似的位置变化效应，尽管CS期间吸气肌的缩短仅达到ES期间观察到幅度的四分之一到三分之一。我们得出结论，颈部解剖结构的位置改变对激活的GG和GH的缩短幅度有显著影响，这可能会大幅降低它们保护咽部通畅的能力。
