The effects of external diaphragmatic pacing on diaphragm function and weaning outcomes of critically ill patients with mechanical ventilation: a prospective randomized study

Abstract

Background: Diaphragmatic pacing can improve diaphragm function, which is beneficial for the prognosis of patients treated with prolonged mechanical ventilation (MV). While most previous studies have focused on the role of implanted diaphragm pacing (IDP), our study is the first to examine the effects of external diaphragmatic pacing (EDP) in mechanically ventilated patients. Specifically, the effect of EDP on diaphragm function, the success rate of weaning, the duration of MV (DMV), and the intensive care unit (ICU) length of stay (ILOS) were assessed. Methods: From September 2019 to December 2020, a total of 51 mechanically ventilated patients in the ICU of the Sun Yat-sen Memorial Hospital, Sun Yat-sen University were enrolled and randomly divided into an EDP group of 27 patients and a control group of 24 patients. The control group received routine treatment, and the EDP group received EDP treatment in addition to routine treatment. The diaphragm excursion (DE), diaphragm thickening fraction (DTF), DMV, ILOS, and average survival time were recorded to evaluate efficacy. Results: Patients treated with EDP had increased DE [exp(B) =1.86, 95% CI: 1.39 to 2.50, P<0.001] and DTF [exp(B) =1.35, 95% CI: 1.05 to 1.76, P=0.022], shortened weaning time (P=0.026) and prolonged average survival time (P<0.001) compared to patients who did not receive EDP therapy. Especially in cases with difficult weaning, the improvement of DE and DTF in the EDP treatment group was more obvious than that in the control group (P=0.013 and P=0.032). Moreover, the DTF upon attempted spontaneous breathing trial (SBT) was negatively correlated with the fraction of inspired oxygen (FiO 2 ) [r=−0.54; 95% confidence interval (CI): −0.77 to −0.19; P=0.004], the arterial partial pressure of oxygen (PaO 2 ) (r=−0.58; 95% CI: −0.79 to −0.25; P=0.001), the PaO 2 /FiO 2 ratio (r=−0.52; 95% CI: −0.75 to −0.16; P=0.006), and the serum lactate concentration (Lac) (r=−0.39; 95% CI: −0.68 to 0.003; P=0.046). Conclusions: EDP treatment can effectively reduce the DMV and prolong the average survival time of mechanically ventilated patients.

Closed‐loop parameter optimization for patient‐specific phrenic nerve stimulation

“…It is important to note that the stimulation frequency of 50 Hz used here for non‐invasive stimulation of the phrenic nerve is significantly greater than that typically used for implanted phrenic nerve stimulation using surgically implanted electrodes within the thorax 18 and is higher than the stimulation frequency used typically in these implanted settings based on animal models demonstrating fatigue at higher stimulation frequencies 19 . However, previous work on the response of the phrenic nerve to non‐invasive stimulation suggests that higher frequencies are required to produce a reliable response non‐invasively, 12 and this is within the range used in studies of non‐invasive diaphragm pacing 17 . Furthermore, stimulation is delivered as short bursts intended to produce contractions for diaphragm exercise with significant rest periods between contractions rather than the regular pacing paradigm used in these studies, lessening the risk of a deleterious effect of stimulation with higher frequencies in this setting.…”

“…19 However, previous work on the response of the phrenic nerve to noninvasive stimulation suggests that higher frequencies are required to produce a reliable response non-invasively, 12 and this is within the range used in studies of non-invasive diaphragm pacing. 17 Furthermore, stimulation is delivered as short bursts intended to produce contractions for diaphragm exercise with significant rest periods between contractions rather than the regular pacing paradigm used in these studies, lessening the risk of a deleterious effect of stimulation with higher frequencies in this setting.…”

“…This ability to automatically determine individualized parameters has significant advantages over comparable methods. Previous trials of external electrical stimulation have relied on detailed individual calibration of electrode position and parameters using diaphragm ultrasound and manual alteration of parameters until a response is observed, 17 requiring significant time commitment as well as specialist training. While methods such as trans‐venous, 6 percutaneous, 8 and surgical 10 stimulation all require implantation procedures with the associated time and skilled staff required to carry out electrode placement and calibrate the response.…”

Phrenic nerve stimulation to prevent diaphragmatic dysfunction and ventilator-induced lung injury

“…The techniques for PNS can be classified as invasive electrical [ 48 , 52 – 56 ], non-invasive electrical [ 57 ] or non-invasive (electro)magnetic [ 11 ] (Fig. 2 ).…”

“…The nomenclature of the stimulation techniques was adopted from the studies in which they were first used for this particular study population. Nevertheless, the terms "EDP" [ 57 ] and "DPS" [ 48 ] have been marginally revised to improve categorisation, differentiation and comprehensibility with respect to the other existing techniques [ 11 , 52 – 56 ] …”