Hughes Stephen, Liu Haipeng, Zheng Dingchang
Medical Devices Research Group, Anglia Ruskin University, Chelmsford, United Kingdom.
Faculty Research Centre for Intelligent Healthcare, Coventry University, Coventry, United Kingdom.
Front Physiol. 2020 Jul 9;11:823. doi: 10.3389/fphys.2020.00823. eCollection 2020.
Respiration frequency (RF) could be derived from the respiratory signals recorded by accelerometers which detect chest wall movements. The optimum direction of acceleration for accurate RF measurement is still uncertain. We aim to investigate the effect of measure site, posture, and direction of acceleration on the accuracy of accelerometer-based RF estimation.
In supine and seated postures respectively, respiratory signals were measured from 34 healthy subjects in 70 s by triaxial accelerometers located at four sites on the body wall (over the clavicle, laterally on the chest wall, over the pectoral part of the anterior chest wall, on the abdomen in the midline at the umbilicus), with the reference respiratory signal simultaneously recorded by a strain gauge chest belt. RFs were extracted from the accelerometer and reference respiratory signals using wavelet transformation. To investigate the effect of measure site, posture, and direction of acceleration on the accuracy of accelerometer-based RF estimation, repeated measures multivariate analysis of variance, linear regression, Bland-Altman analysis, and Scheirer-Ray-Hare test were performed between reference and accelerometer-based RFs.
There was no significant difference in accelerometer-based RF estimation between seated and supine postures, among four accelerometer sites, or between seated or supine postures ( > 0.05 for all). The error of accelerometer-based RF estimation was less than 0.03 Hz (two breaths per minute) at any site or posture, but was significantly smaller in supine posture than in seated posture ( < 0.05), with narrower limits of agreement in Bland-Altman analysis and higher accuracy in linear regression ( > 0.61 vs. < 0.51).
Respiration frequency can be accurately measured from the acceleration of any direction using triaxial accelerometers placed at the clavicular, pectoral and lateral sites on the chest as well the mid abdominal site. More accurate RF estimation could be achieved in supine posture compared with seated posture.
呼吸频率（RF）可从检测胸壁运动的加速度计记录的呼吸信号中得出。用于准确测量RF的最佳加速度方向仍不确定。我们旨在研究测量部位、姿势和加速度方向对基于加速度计的RF估计准确性的影响。
分别在仰卧位和坐位时，通过位于胸壁四个部位（锁骨上方、胸壁外侧、前胸壁胸肌部位、脐部中线腹部）的三轴加速度计，对34名健康受试者进行70秒的呼吸信号测量，同时用应变片胸带记录参考呼吸信号。使用小波变换从加速度计和参考呼吸信号中提取RF。为了研究测量部位、姿势和加速度方向对基于加速度计的RF估计准确性的影响，在参考RF和基于加速度计的RF之间进行了重复测量多变量方差分析、线性回归、布兰德-奥特曼分析和谢勒-雷-黑尔检验。
基于加速度计的RF估计在坐位和仰卧位之间、四个加速度计部位之间或坐位与仰卧位之间均无显著差异（所有P>0.05）。在任何部位或姿势下，基于加速度计的RF估计误差均小于0.03Hz（每分钟两口气），但仰卧位时的误差明显小于坐位（P<0.05），布兰德-奥特曼分析中的一致性界限更窄，线性回归中的准确性更高（r>0.61对r<0.51）。
使用放置在胸部锁骨、胸肌和外侧部位以及腹部中线部位的三轴加速度计，可以从任何方向的加速度准确测量呼吸频率。与坐位相比，仰卧位可实现更准确的RF估计。
