Data from: Noninvasive assessment of respiratory muscle strength and activity in Myotonic dystrophy

Objective
To evaluate sensitivity/specificity of the maximum relaxation rate (MRR) of inspiratory muscles, amplitude of electromyographic activity of the sternocleidomastoid (SCM), scalene (SCA), parasternal (2ndIS) and rectus abdominis (RA) muscles; lung function and respiratory muscle strength in subjects with Myotonic dystrophy type 1 (DM1) compared with healthy subjects.
Design and methods
Quasi-experimental observational study with control group. MRR of inspiratory muscles, lung function and amplitude of the electromyographic activity of SCM, SCA, 2ndIS and RA muscles during maximum inspiratory pressure (PImax), maximum expiratory pressure (PEmax) and sniff nasal inspiratory pressure (SNIP) tests were assessed in eighteen DM1 subjects and eleven healthy.
Results
MRR was lower in DM1 group compared to healthy (P = 0.001) and was considered sensitive and specific to identify disease in DM1 and discard it in controls, as well as SNIP% (P = 0.0026), PImax% (P = 0.0077) and PEmax% (P = 0.0002). Contraction time of SCM and SCA was higher in DM1 compared to controls, respectively, during PImax (P = 0.023 and P = 0.017) and SNIP (P = 0.015 and P = .0004). The DM1 group showed lower PImax (P = .0006), PEmax (P = 0.0002), SNIP (P = 0.0014), and higher electromyographic activity of the SCM (P = 0.002) and SCA (P = 0.004) at rest; of 2ndIS (P = 0.003) during PEmax and of SCM (P = 0.02) and SCA (P = 0.03) during SNIP test.
Conclusions
MD1 subjects presented restrictive pattern, reduced respiratory muscle strength, muscular electrical activity and MRR when compared to higher compared to controls. In addition, the lower MRR found in MD1 subjects showed to be reliable to sensitivity and specificity in identifying the delayed relaxation of respiratory muscles.

### 研究目标
评估吸气肌最大松弛率（maximum relaxation rate, MRR）、胸锁乳突肌（sternocleidomastoid, SCM）、斜角肌（scalene, SCA）、胸骨旁肌（parasternal, 2ndIS）及腹直肌（rectus abdominis, RA）的肌电活动振幅，对比1型强直性肌营养不良（Myotonic dystrophy type 1, DM1）患者与健康受试者的肺功能及呼吸肌力量，以分析上述指标的诊断灵敏度与特异度。

### 研究设计与方法
本研究为带有对照组的准实验性观察性研究。纳入18名1型强直性肌营养不良患者及11名健康受试者，评估其吸气肌最大松弛率、肺功能，以及在最大吸气压力（maximum inspiratory pressure, PImax）、最大呼气压力（maximum expiratory pressure, PEmax）与鼻吸气压（sniff nasal inspiratory pressure, SNIP）测试中，胸锁乳突肌、斜角肌、胸骨旁肌及腹直肌的肌电活动振幅。

### 研究结果
与健康对照组相比，1型强直性肌营养不良患者的吸气肌最大松弛率更低（P=0.001），且该指标对鉴别1型强直性肌营养不良患者与健康对照具有良好的灵敏度与特异度；鼻吸气压百分比（SNIP%，P=0.0026）、最大吸气压力百分比（PImax%，P=0.0077）及最大呼气压力百分比（PEmax%，P=0.0002）亦表现出相似的诊断效能。在最大吸气压力测试中，1型强直性肌营养不良患者的胸锁乳突肌与斜角肌收缩时间分别长于对照组（P=0.023、P=0.017）；在鼻吸气压测试中则分别为P=0.015与P=0.0004。此外，1型强直性肌营养不良患者在静息状态下的最大吸气压力（PImax，P=0.0006）、最大呼气压力（PEmax，P=0.0002）及鼻吸气压（SNIP，P=0.0014）均更低，且胸锁乳突肌（P=0.002）、斜角肌（P=0.004）的静息肌电活动更高；在最大呼气压力测试中，胸骨旁肌的肌电活动更高（P=0.003）；在鼻吸气压测试中，胸锁乳突肌（P=0.02）与斜角肌（P=0.03）的肌电活动更高。

### 研究结论
相较于健康对照组，1型强直性肌营养不良患者呈现限制性通气模式、呼吸肌力量减弱、肌电活动异常及最大松弛率降低。此外，1型强直性肌营养不良患者较低的最大松弛率可可靠地用于识别呼吸肌松弛延迟情况，且具备良好的灵敏度与特异度。