Shkoukani Mahdi, Babcock Mark A, Badr M Safwan
Medical Service, John D. Dingell Veterans Affairs Medical Center, Department of Medicine, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
J Appl Physiol (1985). 2002 Jun;92(6):2565-70. doi: 10.1152/japplphysiol.00938.2001.
We hypothesized that long-term facilitation (LTF) is due to decreased upper airway resistance (Rua). We studied 11 normal subjects during stable non-rapid eye movement sleep. We induced brief isocapnic hypoxia (inspired O(2) fraction = 8%) (3 min) followed by 5 min of room air. This sequence was repeated 10 times. Measurements were obtained during control, hypoxia, and at 20 min of recovery (R(20)) for ventilation, timing, and Rua. In addition, nine subjects were studied in a sham study with no hypoxic exposure. During the episodic hypoxia study, inspiratory minute ventilation (VI) increased from 7.1 +/- 1.8 l/min during the control period to 8.3 +/- 1.8 l/min at R(20) (117% of control; P < 0.05). Conversely, there was no change in diaphragmatic electromyogram (EMG(dia)) between control (16.1 +/- 6.9 arbitrary units) and R(20) (15.3 +/- 4.9 arbitrary units) (95% of control; P > 0.05). In contrast, increased VI was associated with decreased Rua from 10.7 +/- 7.5 cmH(2)O. l(-1). s during control to 8.2 +/- 4.4 cmH(2)O. l(-1). s at R(20) (77% of control; P < 0.05). No change was noted in VI, Rua, or EMG(dia) during the recovery period relative to control during the sham study. We conclude the following: 1) increased VI in the recovery period is indicative of LTF, 2) the lack of increased EMG(dia) suggests lack of LTF to the diaphragm, 3) reduced Rua suggests LTF of upper airway dilators, and 4) increased VI in the recovery period is due to "unloading" of the upper airway by LTF of upper airway dilators.
我们假设长期易化（LTF）是由于上气道阻力（Rua）降低所致。我们在11名正常受试者处于稳定的非快速眼动睡眠状态时进行了研究。我们诱导短暂的等碳酸血症性低氧（吸入氧分数 = 8%）（3分钟），随后给予5分钟的室内空气。该序列重复10次。在对照、低氧期间以及恢复20分钟（R(20)）时获取通气、时间及Rua的测量值。此外，对9名受试者进行了无低氧暴露的假手术研究。在间歇性低氧研究中，吸气分钟通气量（VI）从对照期的7.1±1.8升/分钟增加至R(20)时的8.3±1.8升/分钟（为对照值的117%；P < 0.05）。相反，对照时（16.1±6.9任意单位）与R(20)时（15.3±4.9任意单位）的膈肌肌电图（EMG(dia)）无变化（为对照值的95%；P > 0.05）。相比之下，VI增加与Rua降低相关，Rua从对照时的10.7±7.5厘米水柱·升⁻¹·秒降至R(20)时的8.2±4.4厘米水柱·升⁻¹·秒（为对照值的77%；P < 0.05）。在假手术研究的恢复期，相对于对照，VI、Rua或EMG(dia)均未发现变化。我们得出以下结论：1）恢复期VI增加表明存在LTF；2）EMG(dia)未增加提示对膈肌不存在LTF；3）Rua降低提示上气道扩张肌存在LTF；4）恢复期VI增加是由于上气道扩张肌的LTF对上气道的“卸载”作用。
