Rohrbach Markus, Perret Claudio, Kayser Bengt, Boutellier Urs, Spengler Christina M
Exercise Physiology, Institute for Human Movement Sciences, Swiss Federal Institute of Technology, and Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Eur J Appl Physiol. 2003 Oct;90(3-4):405-10. doi: 10.1007/s00421-003-0871-x. Epub 2003 Jun 24.
The use of non-invasive resistive breathing to task failure to assess inspiratory muscle performance remains a matter of debate. CO2 retention rather than diaphragmatic fatigue was suggested to limit endurance during inspiratory resistive breathing. Cervical magnetic stimulation (CMS) allows discrimination between diaphragmatic and rib cage muscle fatigue. We tested a new protocol with respect to the extent and the partitioning of inspiratory muscle fatigue at task failure. Nine healthy subjects performed two runs of inspiratory resistive breathing at 67 (12)% of their maximal inspiratory mouth pressure, respiratory rate (fR), paced at 18 min(-1), with a 15-min pause between runs. Diaphragm and rib cage muscle contractility were assessed from CMS-induced esophageal (P(es,tw)), gastric (P(ga,tw)), and transdiaphragmatic (P(di,tw)) twitch pressures. Average endurance times of the first and second runs were similar [9.1 (6.7) and 8.4 (3.5) min]. P(di,tw) significantly decreased from 33.1 to 25.9 cmH2O in the first run, partially recovered (27.6 cmH2O), and decreased further in the second run (23.4 cmH2O). P(es,tw) also decreased significantly (-5.1 and -2.4 cmH2O), while P(ga,tw) did not change significantly (-2.0 and -1.9 cmH2O), indicating more pronounced rib cage rather than diaphragmatic fatigue. End-tidal partial pressure of CO2 ( PETCO2) rose from 37.2 to 44.0 and 45.3 mmHg, and arterial oxygen saturation (SaO2) decreased in both runs from 98% to 94%. Thus, task failure in mouth-pressure-targeted, inspiratory resistive breathing is associated with both diaphragmatic and rib cage muscle fatigue. Similar endurance times despite different degrees of muscle fatigue at the start of the runs indicate that other factors, e.g. increases in PETCO2, and/or decreases in SaO2, probably contributed to task-failure.
使用无创性阻力呼吸来评估吸气肌功能直至任务失败仍存在争议。有人认为是二氧化碳潴留而非膈肌疲劳限制了吸气阻力呼吸期间的耐力。颈部磁刺激（CMS）可区分膈肌和胸廓肌肉疲劳。我们针对任务失败时吸气肌疲劳的程度和分布测试了一种新方案。9名健康受试者以其最大吸气口腔压力的67（12）%进行了两轮吸气阻力呼吸，呼吸频率（fR）设定为18次/分钟，两轮之间有15分钟的间歇。通过CMS诱发的食管（P（es,tw））、胃（P（ga,tw））和跨膈（P（di,tw））抽搐压力来评估膈肌和胸廓肌肉的收缩力。第一轮和第二轮的平均耐力时间相似[9.1（6.7）分钟和8.4（3.5）分钟]。第一轮中P（di,tw）从33.1厘米水柱显著降至25.9厘米水柱，部分恢复（27.6厘米水柱），第二轮进一步下降（23.4厘米水柱）。P（es,tw）也显著下降（-5.1和-2.4厘米水柱），而P（ga,tw）没有显著变化（-2.0和-1.9厘米水柱），表明胸廓肌肉疲劳比膈肌疲劳更明显。呼气末二氧化碳分压（PETCO2）从37.2毫米汞柱升至44.0和45.3毫米汞柱，两轮中动脉血氧饱和度（SaO2）均从98%降至94%。因此，以口腔压力为目标的吸气阻力呼吸任务失败与膈肌和胸廓肌肉疲劳均相关。尽管两轮开始时肌肉疲劳程度不同，但耐力时间相似，这表明其他因素，如PETCO2升高和/或SaO2降低，可能导致了任务失败。
