Estimation Of The Neural Inspiratory Time Using Fix Sample Entropy-based Diaphragm Electromyography

BackgroundNon-invasive positive pressure ventilation(NPPV)is an important respiratory support strategy,which can assist ventilation via different interfaces(nasal,oral-nasal,full-face mask and,etc.)without establishing an artificial airway.NPPV can reduce the burden of respiratory muscles,improve carbon dioxide retention,alleviate shortness of breath and other symptoms.It can be used to not only treat chronic obstructive pulmonary disease(COPD)patients at rest,but also assist patients receiving pulmonary rehabilitation.Patient-ventilator synchrony(PVA),which has a greater impact on the treatment effect,is an essential quality control index for the use of NPPV.It objectively describes the coordination of the ventilator’s air supply and the patient’s breathing efforts.The detection of neural inspiratory time is an important aspect in evaluating the PVA,which can be obtained through the following signals: esophageal electromyogram of diaphragm(e EMGdi),surface electromyogram of respiratory muscle(s EMG),esophageal pressure(Peso),transdiaphragmatic pressure(Pdi),flow and airway pressure(Paw).EMGdi,the earliest inspiratory effort signal that can be detected,has attracted particular attention from many researchers.But the EMGdi presents as the spike-wave and is susceptible to the electrocardiography(ECG),which makes it being hard to analyze.Therefore,the optimization of electromyography has been studied in the past decades,and the key question is to reduce the interference of ECG.Various methods were used to remove the noise of ECG.However,the spectrum of EMGdi partly overlaps with those of ECG,and it will inevitably weaken the EMGdi after removing the noise of ECG.Fixed sample entropy(f SE)can obtain a regular and smooth waveform from raw EMGdi without ECG filtering.But the consistency between the f SE-e EMGdi and RMS-e EMGdi is still unknown.Furthermore,the differences among f SE-e EMGdi,Peso,Pdi and flow in detecting the onset,offset and duration of neural inspiratory time are still needed to explore in different populations and different physiological states.Objectives1.To explore the accuracy of f SE-e EMGdi to monitor the onset and end of EMGdi,comparing with RMS-e EMGdi.2.To compare the differences among f SE-e EMGdi and esophageal pressure,transdiaphragmatic pressure,and flow in detecting the onset,offset and duration of neural inspiratory time during spontaneous breath in normal subjects and COPD patients.3.To identify the neural inspiratory time through the f SE-e EMGdi when subjects received NPPV at rest or during exercise and to compare the physiological parameters at different conditions.Methods11 normal subjects and 8 stable COPD patients were enrolled,and their e EMG,Peso,Pdi,and Flow during the spontaneous breath,receiving NPPV at rest and using NPPV to assist exercise.Eight stable breathing cycles were extracted from each subject for analysis.After processing the original EMG data through f SE and RMS,the data were compared with the original EMGdi to evaluate their consistency.The onset,offset and duration of neural inspiratory time were detected using f SE-e EMGdi,Peso,Pdi and Flow among different populations and different conditions,respectively.Results1.After processing the original EMG signals of 137 respiration cycles using the f SE and RMS methods,it is found that Ton(f SE-e EMGdi)is closer to Ton(raw-e EMGdi)in the detection of onset than Ton(RMS-e EMGdi),and the distribution is more concentrated [-49(-124,42)ms vs-148(-313,47)ms)].Tex(f SE-e EMGdi)is closer to Tex(Raw-e EMGdi)than Tex(RMS-e EMGdi)[108(30,204)ms vs 251(26,448)ms].2.During spontaneous breath,Ton(f SE-e EMGdi)could be first detected,and followed by Ton(Peso)(82 ± 144 ms,p <0.01),Ton(Pdi)(139 ± 114ms),P <0.0001),and Ton(Flow)(230 ± 119 ms,p <0.0001).No statistically significant difference could be detected between Toff(Peso),Toff(Pdi)and Toff(f SE-e EMGdi),while Toff(Flow)have a significant lag(150 ± 65 ms,p <0.0001)in COPD subjects.No statistically significant differences were found among different signals in detecting the onset While Toff(Peso)(-118 ± 114 ms,p <0.0001)and Toff(Pdi)(-53 ± 135 ms,p <0.001)appeared earlier than Toff(f SE-e EMGdi),and followed by Toff(Flow)(272 ± 121 ms,p <0.0001).3.During receiving NPPV at rest,the Ton(f SE-e EMGdi)is still the earliest signal,followed by Ton(Peso)(71 ± 107 ms,p <0.01),Ton(Pdi)(88 ± 121 ms,p <0.001)and Ton(Flow)(213 ± 119 ms,p <0.0001).While Toff(Peso)(-163 ± 174 ms,p <0.001),Toff(Pdi)(-109 ± 118 ms,p <0.001)appeared earlier than Toff(f SE-e EMGdi),yet Toff(Flow)still showed a lag(366 ± 92 ms,p <0.001)in the COPD subjects.In normal subjects,no significant difference was found between Ton(Peso),Ton(Pdi)and Ton(f SE-e EMGdi);however,Ton(Flow)showed a lag(63 ± 167 ms,p <0.01).And the Toff(Peso)(-118 ±114ms,p <0.0001)and Toff(Pdi)(-53 ± 135 ms,p <0.001)appeared earlier than Toff(f SE-e EMGdi),followed by Toff(Flow)(272 ± 121 ms,p <0.0001).4.During receiving NPPV to assist exercise,Ton(f SE-e EMGdi)is still the earliest signal,followed by Ton(Peso)(53 ± 65 ms,p <0.001),Ton(Pdi)(71 ± 60 ms,p <0.0001)and Ton(Flow)(189 ± 158 ms,p <0.0001).But Toff(Peso)(-145 ± 114 ms,p <0.001),Toff(Pdi)(-166 ± 144 ms,p <0.001)appeared earlier than Toff(f SE-e EMGdi),followed by Toff(Flow)(85 ± 52 ms,p <0.001)in the COPD subjects.In the normal subjects,Ton(Peso)(-106 ± 156 ms,p <0.001)and Ton(Pdi)(-82 ± 138 ms,p <0.001)detected onset earlier than Ton(f SE-e EMGdi),while Ton(Flow)show a lag(48 ± 151 ms,p <0.01).Toff(Peso)(-131 ± 119 ms,p <0.0001)and Toff(Pdi)(-77 ± 121 ms,p < 0.0001)appeared earlier than Toff(f SE-e EMGdi),yet Toff(Flow)showed a lag(111 ± 73 ms,p <0.0001).Conclusions1.Using f SE to process the raw EMGdi can obtain a relatively smooth and regular waveforms without filtering ECG.Compared with RMS,it showed a closer detection result to the raw EMGdi.2.In COPD subjects,f SE-e EMGdi is the earliest signal to detect the onset of neural inspiratory time,followed by Peso,Pdi,and Flow.But in normal subjects,f SE-e EMGdi showed no significant difference in detecting the onset when comparing with Peso,Pdi,and Flow.3.When receiving NPPV at rest or to assist exercise,f SE-e EMGdi is the earliest physiological signal of monitoring the neural inspiratory time in COPD patients.Although the differences among the neural inspiratory time are smaller when compared with other monitoring indicators,it is also an ideal trigger signal for ventilators.