Illidi Camilla R, Romer Lee M
Division of Sport, Health and Exercise Sciences, College of Health, Medicine and Life Sciences, Brunel University London, Uxbridge, UK.
Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, Québec, Canada.
Exp Physiol. 2025 Mar;110(3):478-493. doi: 10.1113/EP092322. Epub 2025 Jan 9.
Assessment of diaphragm function and fatigue typically relies on the measurement of transdiaphragmatic pressure (P). Although P serves as an index of diaphragm force output, it provides limited information regarding the ability of the muscle to shorten and generate power. We asked whether ultrasonography, combined with P, could be used to quantify changes in diaphragm function attributable to fatigue. Eight healthy men [mean (SD) age, 23 (7) years] completed two tasks on separate occasions: (i) 2 min of maximal isocapnic ventilation (MIV); or (ii) 3 × 5 min of maximal inspiratory resistive loading (IRL). Diaphragm function was evaluated before (PRE) and after each task (POST, 10-15 min and POST, 30-35 min) using synchronous recordings of P and subcostal ultrasound traces of the right crural hemidiaphragm during anterolateral magnetic stimulation of the phrenic nerves and progressive CO rebreathing. Fatigue was quantified as pre- to post-loading changes in twitch P, excursion velocity (excursion/time) and power (P × velocity). Both tasks resulted in significant reductions in twitch P (P < 0.05). There were no effects of MIV on ultrasound-derived measures. In contrast, IRL elicited a significant reduction in twitch excursion at POST (-16%; P = 0.034) and significant reductions in excursion velocity at POST (-32%; P = 0.022) and POST (-28%; P = 0.013). These reductions in excursion velocity, alongside the concurrent reductions in twitch P, resulted in significant reductions in diaphragm power at POST (-48%; P = 0.009) and POST (-42%; P = 0.008). Neither task significantly altered the contractile responses to CO. In conclusion, subcostal ultrasonography coupled with phrenic nerve stimulation is a promising method for quantifying contractile fatigue of the human diaphragm.
膈肌功能和疲劳的评估通常依赖于跨膈压（P）的测量。尽管P可作为膈肌力量输出的指标，但它提供的关于肌肉缩短和产生力量能力的信息有限。我们探讨了超声检查结合P是否可用于量化因疲劳导致的膈肌功能变化。八名健康男性[平均（标准差）年龄，23（7）岁]在不同时间完成了两项任务：（i）2分钟的最大等碳酸通气（MIV）；或（ii）3×5分钟的最大吸气阻力负荷（IRL）。在每项任务前（PRE）和后（POST，10 - 15分钟和POST，30 - 35分钟），通过在膈神经前外侧磁刺激和渐进性CO再呼吸期间同步记录P和右膈脚半膈肌的肋下超声轨迹来评估膈肌功能。疲劳程度通过负荷前后颤搐P、偏移速度（偏移/时间）和功率（P×速度）的变化来量化。两项任务均导致颤搐P显著降低（P < 0.05）。MIV对超声衍生指标无影响。相比之下，IRL导致POST时颤搐偏移显著降低（-16%；P = 0.034），POST时偏移速度显著降低（-32%；P = 0.022）以及POST时（-28%；P = 0.013）。这些偏移速度的降低，连同颤搐P的同时降低，导致POST时膈肌功率显著降低（-48%；P = 0.009）和POST时（-42%；P = 0.008）。两项任务均未显著改变对CO的收缩反应。总之，肋下超声检查结合膈神经刺激是一种用于量化人膈肌收缩性疲劳的有前景的方法。
