Electrical Activity Of Diaphragm Research Articles

Advanced Respiratory Monitoring during Extracorporeal Membrane Oxygenation.

Advanced respiratory monitoring encompasses a diverse range of mini- or noninvasive tools used to evaluate various aspects of respiratory function in patients experiencing acute respiratory failure, including those requiring extracorporeal membrane oxygenation (ECMO) support. Among these techniques, key modalities include esophageal pressure measurement (including derived pressures), lung and respiratory muscle ultrasounds, electrical impedance tomography, the monitoring of diaphragm electrical activity, and assessment of flow index. These tools play a critical role in assessing essential parameters such as lung recruitment and overdistention, lung aeration and morphology, ventilation/perfusion distribution, inspiratory effort, respiratory drive, respiratory muscle contraction, and patient-ventilator synchrony. In contrast to conventional methods, advanced respiratory monitoring offers a deeper understanding of pathological changes in lung aeration caused by underlying diseases. Moreover, it allows for meticulous tracking of responses to therapeutic interventions, aiding in the development of personalized respiratory support strategies aimed at preserving lung function and respiratory muscle integrity. The integration of advanced respiratory monitoring represents a significant advancement in the clinical management of acute respiratory failure. It serves as a cornerstone in scenarios where treatment strategies rely on tailored approaches, empowering clinicians to make informed decisions about intervention selection and adjustment. By enabling real-time assessment and modification of respiratory support, advanced monitoring not only optimizes care for patients with acute respiratory distress syndrome but also contributes to improved outcomes and enhanced patient safety.

Skin-to-Skin Contact and Diaphragm Electrical Activity in Preterm Infants During Noninvasive Pressure Control.

Skin-to-skin contact (SSC) is widely implemented in the neonatal intensive care unit (NICU) due to its established role in reducing mortality and morbidity. However, the impact of SSC on diaphragmatic electrical activity (Edi) in premature infants undergoing noninvasive pressure control (NIV-PC) for respiratory management remains insufficiently explored. To assess the effects of SSC on Edi and vital signs in preterm infants managed with NIV-PC. A prospective, observational, crossover study was conducted, involving preterm infants admitted to a level III NICU between May 2020 and August 2021, who were receiving respiratory support with NIV-PC. Data were collected at 3 distinct time points: before SSC (pre-SSC period), during SSC (SSC period), and after SSC (post-SSC period). Thirty-minute periods of stable data were extracted for analysis. A total of 21 SSC sessions were performed on 14 preterm infants, with a median age at the initiation of SSC of 62 days. The median (interquartile range) Edi peak (in microvolts) before, during, and after SSC was 7.1 (5.8-10.8), 6.8 (4.3-8.8), and 7.1 (5.5-8.8), respectively. No statistically significant differences were observed in Edi peak or minimum values during SSC, when compared with the periods before and after the SSC procedure. Likewise, no significant changes were noted in respiratory rate, oxygen saturation, heart rate, or the incidence of apnea. SSC in preterm infants undergoing NIV-PC does not exacerbate their clinical condition. Further investigations involving diverse patient cohorts are warranted.

Noninvasive Neurally Adjusted Ventilation versus Nasal Continuous or Intermittent Positive Airway Pressure for Preterm Infants: A Systematic Review and Meta-Analysis.

The noninvasive neurally adjusted ventilatory assist (NIV-NAVA) is a newly developed noninvasive ventilation technique with promising clinical and ventilatory outcomes for preterm infants. This systematic review and meta-analysis aimed to investigate whether NIV-NAVA has better clinical and ventilatory outcomes than nasal continuous airway pressure (NCPAP) or noninvasive positive pressure ventilation (NIPP) on premature infants. MEDLINE, Embase, and CENTRAL were searched, and randomized controlled trials (RCTs) that compared NIV-NAVA with NCPAP or NIPP for preterm infants (gestational age: <37 weeks) were included. We evaluated the following outcomes in the neonatal intensive care unit: the desaturation rate, failure of noninvasive modality requiring intubation when received as the primary mode or the need for re-intubation after extubation from mechanical ventilation in the secondary mode (weaning), length of stay, and fraction of inspired oxygen. The mean difference and risk ratio were used to represent continuous and dichotomous outcomes, respectively. We included nine RCTs involving 339 preterm infants overall. NIV-NAVA showed similar clinical and ventilatory outcomes to NCPAP or NIPP, except for the maximum diaphragmatic electrical activity. The rate of failure of the noninvasive modality was not statistically different between NIV-NAVA and NCPAP. The pooled estimates for the maximum electrical activity were significantly reduced in NIV-NAVA compared with those in NIPP. The findings suggest that NIV-NAVA may be as safe and effective as NCPAP and NIPP for preterm neonates, particularly those who may not tolerate these alternative noninvasive methods. However, further trials are recommended for greater evidence.

Predicting extubation in patients with traumatic cervical spinal cord injury using the diaphragm electrical activity during a single maximal maneuver

BackgroundThe unsuccessful extubation in patients with traumatic cervical spinal cord injuries (CSCI) may result from impairment diaphragm function and monitoring of diaphragm electrical activity (EAdi) can be informative in guiding extubation. We aimed to evaluate whether the change of EAdi during a single maximal maneuver can predict extubation outcomes in CSCI patients.MethodsThis is a retrospective study of CSCI patients requiring mechanical ventilation in the ICU of a tertiary hospital. A single maximal maneuver was performed by asking each patient to inhale with maximum strength during the first spontaneous breathing trial (SBT). The baseline (during SBT before maximal maneuver), maximum (during the single maximal maneuver), and the increase of EAdi (ΔEAdi, equal to the difference between baseline and maximal) were measured. The primary outcome was extubation success, defined as no reintubation after the first extubation and no tracheostomy before any extubation during the ICU stay.ResultsAmong 107 patients enrolled, 50 (46.7%) were extubated successfully at the first SBT. Baseline EAdi, maximum EAdi, and ΔEAdi were significantly higher, and the rapid shallow breathing index was lower in patients who were extubated successfully than in those who failed. By multivariable logistic analysis, ΔEAdi was independently associated with successful extubation (OR 2.03, 95% CI 1.52–3.17). ΔEAdi demonstrated high diagnostic accuracy in predicting extubation success with an AUROC 0.978 (95% CI 0.941–0.995), and the cut-off value was 7.0 μV.ConclusionsThe increase of EAdi from baseline SBT during a single maximal maneuver is associated with successful extubation and can help guide extubation in CSCI patients.

Noninvasive Neurally Adjusted Ventilatory Assist in Infants With Bronchiolitis: Respiratory Outcomes in a Single-Center, Retrospective Cohort, 2016-2018.

To describe our experience of using noninvasive neurally adjusted ventilatory assist (NIV-NAVA) in infants with bronchiolitis, its association with the evolution of respiratory effort, and PICU outcomes. Retrospective analysis of a prospectively curated, high-frequency electronic database. A PICU in a university-affiliated maternal-child health center in Canada. Patients younger than 2 years old who were admitted with a diagnosis of acute bronchiolitis and treated with NIV-NAVA from October 2016 to June 2018. None. Patient characteristics, as well as respiratory and physiologic parameters, including electrical diaphragmatic activity (Edi), were extracted from the electronic database. Respiratory effort was estimated using the modified Wood Clinical Asthma Score (mWCAS) and the inspiratory Edi. A comparison in the respiratory effort data was made between the 2 hours before and 2 hours after starting NIV-NAVA. In the two seasons, 64 of 205 bronchiolitis patients were supported with NIV-NAVA. These 64 patients had a median (interquartile range [IQR]) age of 52 days (32-92 d), and there were 36 of 64 males. Treatment with NIV-NAVA was used after failure of first-tier noninvasive respiratory support; 25 of 64 patients (39%) had at least one medical comorbidity. NIV-NAVA initiation was associated with a moderate decrease in mWCAS from 3.0 (IQR, 2.5-3.5) to 2.5 (IQR, 2.0-3.0; p < 0.001). NIV-NAVA initiation was also associated with a statistically significant decrease in Edi ( p < 0.01). However, this decrease was only clinically relevant in infants with a 2-hour baseline Edi greater than 20 μV; here, the before and after Edi was 44 μV (IQR, 33-54 μV) compared with 27 μV (IQR, 21-36 μV), respectively ( p < 0.001). Overall, six of 64 patients (9%) required endotracheal intubation. In this single-center retrospective cohort, in infants with bronchiolitis who were considered to have failed first-tier noninvasive respiratory support, the use of NIV-NAVA was associated with a rapid decrease in respiratory effort and a 9% intubation rate.

Physiological effects of high-flow nasal cannula oxygen therapy after extubation: a randomized crossover study

BackgroundProphylactic high-flow nasal cannula (HFNC) oxygen therapy can decrease the risk of extubation failure. It is frequently used in the postextubation phase alone or in combination with noninvasive ventilation. However, its physiological effects in this setting have not been thoroughly investigated. The aim of this study was to determine comprehensively the effects of HFNC applied after extubation on respiratory effort, diaphragm activity, gas exchange, ventilation distribution, and cardiovascular biomarkers.MethodsThis was a prospective randomized crossover physiological study in critically ill patients comparing 1 h of HFNC versus 1 h of standard oxygen after extubation. The main inclusion criteria were mechanical ventilation for at least 48 h due to acute respiratory failure, and extubation after a successful spontaneous breathing trial (SBT). We measured respiratory effort through esophageal/transdiaphragmatic pressures, and diaphragm electrical activity (ΔEAdi). Lung volumes and ventilation distribution were estimated by electrical impedance tomography. Arterial and central venous blood gases were analyzed, as well as cardiac stress biomarkers.ResultsWe enrolled 22 patients (age 59 ± 17 years; 9 women) who had been intubated for 8 ± 6 days before extubation. Respiratory effort was significantly lower with HFNC than with standard oxygen therapy, as evidenced by esophageal pressure swings (5.3 [4.2–7.1] vs. 7.2 [5.6–10.3] cmH2O; p < 0.001), pressure–time product (85 [67–140] vs. 156 [114–238] cmH2O*s/min; p < 0.001) and ΔEAdi (10 [7–13] vs. 14 [9–16] µV; p = 0.022). In addition, HFNC induced increases in end-expiratory lung volume and PaO2/FiO2 ratio, decreases in respiratory rate and ventilatory ratio, while no changes were observed in systemic hemodynamics, Troponin T, or in amino-terminal pro-B-type natriuretic peptide.ConclusionsProphylactic application of HFNC after extubation provides substantial respiratory support and unloads respiratory muscles.Trial registration January 15, 2021. NCT04711759.

Estimation of transpulmonary driving pressure during synchronized mechanical ventilation using a single lower assist maneuver (LAM) in rabbits: a comparison to measurements made with an esophageal balloon

BackgroundMechanical ventilation is applied to unload the respiratory muscles, but knowledge about transpulmonary driving pressure (ΔPL) is important to minimize lung injury. We propose a method to estimate ΔPL during neurally synchronized assisted ventilation, with a simple intervention of lowering the assist for one breath (“lower assist maneuver”, LAM).MethodsIn 24 rabbits breathing spontaneously with imposed loads, titrations of increasing assist were performed, with two neurally synchronized modes: neurally adjusted ventilatory assist (NAVA) and neurally triggered pressure support (NPS). Two single LAM breaths (not sequentially, but independently) were performed at each level of assist by acutely setting the assist to zero cm H2O (NPS) or NAVA level 0 cm H2O/uV (NAVA) for one breath. NPS and NAVA titrations were followed by titrations in controlled-modes (volume control, VC and pressure control, PC), under neuro-muscular blockade. Breaths from the NAVA/NPS titrations were matched (for flow and volume) to VC or PC. Throughout all runs, we measured diaphragm electrical activity (Edi) and esophageal pressure (PES). We measured ΔPL during the spontaneous modes (PL_PES) and controlled mechanical ventilation (CMV) modes (PL_CMV) with the esophageal balloon. From the LAMs, we derived an estimation of ΔPL (“PL_LAM”) using a correction factor (ratio of volume during the LAM and volume during assist) and compared it to measured ΔPL during passive (VC or PC) and spontaneous breathing (NAVA or NPS). A requirement for the LAM was similar Edi to the assisted breath.ResultsAll animals successfully underwent titrations and LAMs for NPS/NAVA. One thousand seven-hundred ninety-two (1792) breaths were matched to passive ventilation titrations (matched Vt, r = 0.99). PL_LAM demonstrated strong correlation with PL_CMV (r = 0.83), and PL_PES (r = 0.77). Bland–Altman analysis revealed little difference between the predicted PL_LAM and measured PL_CMV (Bias = 0.49 cm H2O and 1.96SD = 3.09 cm H2O). For PL_PES, the bias was 2.2 cm H2O and 1.96SD was 3.4 cm H2O. Analysis of Edi and PES at peak Edi showed progressively increasing uncoupling with increasing assist.ConclusionDuring synchronized mechanical ventilation, a LAM breath allows for estimations of transpulmonary driving pressure, without measuring PES, and follows a mathematical transfer function to describe respiratory muscle unloading during synchronized assist.

Editor's Choice Articles for June.

Editor's Choice Articles for June.

Monitorización del destete ventilatorio en el paciente crítico

The weaning process can be classified as simple, difficult, or prolonged. The incidence of difficult or prolonged weaning varies from 15% to 25%, according to the series. In critically ill patients it accounts for up to 50% of the total time that they are connected to the ventilator. It is very important to monitor weaning to detect the patients in whom it will be prolonged, and to help us in their management and decision making. Firstly, gas exchange and ventilatory mechanics must be monitored, fundamental in all patients on mechanical ventilation (MV). In addition, monitoring specific parameters that provide information on the patient's respiratory effort is strategic in the weaning process. These parameters include occlusion pressure (P0.1), oesophageal pressure (Poes), Negative Inspiratory Force (NIF), also known as Maximum Inspiratory Pressure (MIP), diaphragmatic electric activity (Edi), total work of breathing (WOB), and its components, elastic WOB (eWOB), and resistive WOB (rWOB). Monitoring weaning from mechanical ventilation means we can establish when the conditions have been met to start the weaning process, propose a weaning protocol adapted to the conditions of the patient, and define our post-extubation respiratory care protocol to prevent weaning failure.

The effect of proportional assist ventilation on the electrical activity of the human diaphragm during exercise.

What is the central question of this study? What is the effect of lowering the normally occurring work of breathing on the electrical activity and pressure generated by the diaphragm during submaximal exercise in healthy humans? What is the main finding and its importance? Ventilatory assist during exercise elicits a proportional lowering of both the work performed by the diaphragm and diaphragm electrical activity. These findings have implications for exercise training studies using proportional assist ventilation to reduce diaphragm work in patients with cardiopulmonary disease. We hypothesized that when a proportional assist ventilator (PAV) is applied in order to reduce the pressure generated by the diaphragm, there would be a corresponding reduction in electrical activity of the diaphragm. Healthy participants (five male and four female) completed an incremental cycle exercise test to exhaustion in order to calculate workloads for subsequent trials. On the experimental day, participants performed submaximal cycling, and three levels of assisted ventilation were applied (low, medium and high). Ventilatory parameters, pulmonary pressures and EMG of the diaphragm (EMGdi ) were obtained. To compare the PAV conditions with spontaneous breathing intervals, ANOVA procedures were used, and significant effects were evaluated with a Tukey-Kramer test. Significance was set at P<0.05. The work of breathing was not different between the lowest level of unloading and spontaneous breathing (P=0.151) but was significantly lower during medium (25%, P=0.02) and high (36%, P<0.001) levels of PAV. The pressure-time product of the diaphragm (PTPdi ) was lower across PAV unloading conditions (P<0.05). The EMGdi was significantly lower in medium and high PAV conditions (P=0.035 and P<0.001, respectively). The mean reductions of EMGdi with PAV unloading were 14, 22 and 39%, respectively. The change in EMGdi for a given lowering of PTPdi with the PAV was significantly correlated (r=0.61, P=0.01). Ventilatory assist during exercise elicits a reduction in the electrical activity of the diaphragm, and there is a proportional lowering of the work of breathing. Our findings have implications for exercise training studies using assisted ventilation to reduce diaphragm work in patients with cardiopulmonary disease.

Diaphragm electrical activity during weaning of nasal high-flow therapy in preterm infants

ObjectiveTo determine whether electrical activity of the diaphragm (Edi) changes with weaning nasal high-flow (HF) therapy in preterm infants according to a standardised protocol.DesignProspective observational cohort study.SettingNeonatal intensive care unit.PatientsPreterm...

Synchronized and proportional sub-diaphragmatic unloading in an animal model of respiratory distress.

A sealed abdominal interface was positioned below the diaphragm (the "NeoVest") to apply synchronized and proportional negative pressure ventilation (NPV) and was compared to positive pressure ventilation (PPV) using neurally adjusted ventilatory assist (NAVA). Both modes were controlled by the diaphragm electrical activity (Edi). Eleven rabbits (mean weight 2.9 kg) were instrumented, tracheotomized, and ventilated with either NPV or PPV (sequentially) with different loads (resistive, dead space, acute lung injury). Assist with either PPV or NPV was titrated to reduce Edi by 50%. In order to achieve a 50% reduction in Edi, NPV required slightly more negative pressure (-8 to -12 cm H2O) than observed in PPV (+6 to +10 cm H2O). The efficiency of pressure transmission from the NeoVest into gastric pressure was 69.6% (range 61.3-77.4%). Swings in esophageal pressure were more negative during NPV than PPV, for all conditions, due to transmission of negative pressure. Transpulmonary pressure was lower during NPV. Transdiaphragmatic pressure swings were reduced similarly for PPV and NPV, suggesting equivalent unloading of the diaphragm. NPV did not affect hemodynamics. It is feasible to apply NPV sub-diaphragmatically in synchrony and in proportion to Edi in an animal model of respiratory distress. Negative pressure ventilation (NPV), for example, the "Iron Lung," may offer advantages over positive pressure ventilation. In the present work, we describe the "NeoVest," a system consisting of a sealed abdominal interface and a ventilator that applies NPV in synchrony and in proportion to the diaphragm electrical activity (Edi).

NIV-NAVA versus NCPAP immediately after birth in premature infants: A randomized controlled trial

ObjectiveTo evaluate whether noninvasive-neurally adjusted ventilatory assist (NIV-NAVA) decrease respiratory efforts compared to nasal continuous positive airway pressure (NCPAP) during the first hours of life. MethodsTwenty infants born between 28+0 and 31+6 weeks were randomized to NIV-NAVA or NCPAP. Positive end-expiratory pressure was constantly kept at 6 cmH2O for both groups and the NAVA level was 1.0 cmH2O/µV for NIV-NAVA group. The electrical activity of diaphragm (Edi) were recorded for the first two hours. ResultsPeak and minimum Edi decreased similarly in both groups (P = 0.98 and P = 0.59, respectively). Leakages were higher in the NIV-NAVA group than in the NCPAP group (P < 0.001). The neural apnea defined as a flat Edi for ≥ 5 s were less frequent in NIV-NAVA group than in NCPAP group (P = 0.046). ConclusionsImmediately applied NIV-NAVA in premature infants did not reduce breathing effort, measured as peak Edi. However, NIV-NAVA decreased neural apneic episodes compared to NCPAP.

Pulmonary volume-feedback and ventilatory pattern after bilateral lung transplantation using neurally adjusted ventilatory assist ventilation

BackgroundBilateral lung transplantation results in pulmonary vagal denervation, which potentially alters respiratory drive, volume-feedback, and ventilatory pattern. We hypothesised that Neurally Adjusted Ventilatory Assist (NAVA) ventilation, which is driven by diaphragm electrical activity (EAdi), would reveal whether vagally mediated pulmonary-volume feedback is preserved in the early phases after bilateral lung transplantation. MethodsWe prospectively studied bilateral lung transplant recipients within 48 h of surgery. Subjects were ventilated with NAVA and randomised to receive 3 ventilatory modes (baseline NAVA, 50%, and 150% of baseline NAVA values) and 2 PEEP levels (6 and 12 cm H2O). We recorded airway pressure, flow, and EAdi. ResultsWe studied 30 subjects (37% female; age: 37 (27–56) yr), of whom 19 (63%) had stable EAdi. The baseline NAVA level was 0.6 (0.2–1.0) cm H2O μV−1. Tripling NAVA level increased the ventilatory peak pressure over PEEP by 6.3 (1.8), 7.6 (2.4), and 8.7 (3.2) cm H2O, at 50%, 100%, and 150% of baseline NAVA level, respectively (P<0.001). EAdi peak decreased by 10.1 (9.0), 9.5 (9.4) and 8.8 μV (8.7) (P<0.001), accompanied by small increases in tidal volume, 8.3 (3.0), 8.7 (3.6), and 8.9 (3.3) ml kg−1 donor's predicted body weight at 50%, 100%, and 150% of baseline NAVA levels, respectively (P<0.001). Doubling PEEP did not affect tidal volume. ConclusionsNAVA ventilation was feasible in the majority of patients during the early postoperative period after bilateral lung transplantation. Despite surgical vagotomy distal to the bronchial anastomoses, bilateral lung transplant recipients maintained an unmodified respiratory pattern in response to variations in ventilatory assistance and PEEP. Clinical trial registrationNCT03367221.

Role of a successful spontaneous breathing trial in ventilator liberation in brain-injured patients.

Spontaneous breathing trials (SBTs) have been shown to improve outcomes in critically ill patients. However, in patients with brain injury, indications for intubation and mechanical ventilation are different from those of non-neurological patients, and the role of an SBT in patients with brain injury is less established. The aim of the present study was to compare key respiratory variables acquired during a successful SBT between patients with successful ventilator liberation versus failed ventilator liberation. In this prospective study, patients with brain injury (≥18 years of age), who completed a 30-min SBT, were enrolled. Airway pressure, flow, esophageal pressure, and diaphragm electrical activity (ΔEAdi) were recorded before (baseline) and during the SBT. Respiratory rate (RR), tidal volume, inspiratory muscle pressure (ΔPmus), ΔEAdi, and neuromechanical efficiency (ΔPmus/ΔEAdi) of the diaphragm were calculated breath by breath and compared between the liberation success and failure groups. Failed liberation was defined as the need for invasive ventilator assistance within 48 h after the SBT. In total, 46 patients (51.9±13.2 years, 67.4% male) completed the SBT. Seventeen (37%) patients failed ventilator liberation within 48 h. Another 11 patients required invasive ventilation within 7 days after completing the SBT. There were no differences in baseline characteristics between the success and failed groups. In-depth analysis showed similar changes in patterns and values of respiratory physiological parameters between the groups. In patients with brain injury, ventilator liberation failure was common after successful SBT. In-depth physiological analysis during the SBT did not provide data to predict successful liberation in these patients. The trial was registered at ClinicalTrials.gov (No. NCT02863237).

Neural control of pressure support ventilation improved patient-ventilator synchrony in patients with different respiratory system mechanical properties: a prospective, crossover trial.

BackgroundConventional pressure support ventilation (PSP) is triggered and cycled off by pneumatic signals such as flow. Patient-ventilator asynchrony is common during pressure support ventilation, thereby contributing to an increased inspiratory effort. Using diaphragm electrical activity, neurally controlled pressure support (PSN) could hypothetically eliminate the asynchrony and reduce inspiratory effort. The purpose of this study was to compare the differences between PSN and PSP in terms of patient-ventilator synchrony, inspiratory effort, and breathing pattern.MethodsEight post-operative patients without respiratory system comorbidity, eight patients with acute respiratory distress syndrome (ARDS) and obvious restrictive acute respiratory failure (ARF), and eight patients with chronic obstructive pulmonary disease (COPD) and mixed restrictive and obstructive ARF were enrolled. Patient-ventilator interactions were analyzed with macro asynchronies (ineffective, double, and auto triggering), micro asynchronies (inspiratory trigger delay, premature, and late cycling), and the total asynchrony index (AI). Inspiratory efforts for triggering and total inspiration were analyzed.ResultsTotal AI of PSN was consistently lower than that of PSP in COPD (3% vs. 93%, P = 0.012 for 100% support level; 8% vs. 104%, P = 0.012 for 150% support level), ARDS (8% vs. 29%, P = 0.012 for 100% support level; 16% vs. 41%, P = 0.017 for 150% support level), and post-operative patients (21% vs. 35%, P = 0.012 for 100% support level; 15% vs. 50%, P = 0.017 for 150% support level). Improved support levels from 100% to 150% statistically increased total AI during PSP but not during PSN in patients with COPD or ARDS. Patients’ inspiratory efforts for triggering and total inspiration were significantly lower during PSN than during PSP in patients with COPD or ARDS under both support levels (P < 0.05). There was no difference in breathing patterns between PSN and PSP.ConclusionsPSN improves patient-ventilator synchrony and generates a respiratory pattern similar to PSP independently of any level of support in patients with different respiratory system mechanical properties. PSN, which reduces the trigger and total patient's inspiratory effort in patients with COPD or ARDS, might be an alternative mode for PSP.Trial RegistrationClinicalTrials.gov, NCT01979627; https://clinicaltrials.gov/ct2/show/record/NCT01979627.

Duration of diaphragmatic inactivity after endotracheal intubation of critically ill patients

BackgroundIn patients intubated for mechanical ventilation, prolonged diaphragm inactivity could lead to weakness and poor outcome. Time to resume a minimal diaphragm activity may be related to sedation practice and patient severity.MethodsProspective observational study in critically ill patients. Diaphragm electrical activity (EAdi) was continuously recorded after intubation looking for resumption of a minimal level of diaphragm activity (beginning of the first 24 h period with median EAdi > 7 µV, a threshold based on literature and correlations with diaphragm thickening fraction). Recordings were collected until full spontaneous breathing, extubation, death or 120 h. A 1 h waveform recording was collected daily to identify reverse triggering.ResultsSeventy-five patients were enrolled and 69 analyzed (mean age ± standard deviation 63 ± 16 years). Reasons for ventilation were respiratory (55%), hemodynamic (19%) and neurologic (20%). Eight catheter disconnections occurred. The median time for resumption of EAdi was 22 h (interquartile range 0–50 h); 35/69 (51%) of patients resumed activity within 24 h while 4 had no recovery after 5 days. Late recovery was associated with use of sedative agents, cumulative doses of propofol and fentanyl, controlled ventilation and age (older patients receiving less sedation). Severity of illness, oxygenation, renal and hepatic function, reason for intubation were not associated with EAdi resumption. At least 20% of patients initiated EAdi with reverse triggering.ConclusionLow levels of diaphragm electrical activity are common in the early course of mechanical ventilation: 50% of patients do not recover diaphragmatic activity within one day. Sedatives are the main factors accounting for this delay independently from lung or general severity.Trial Registration ClinicalTrials.gov (NCT02434016). Registered on April 27, 2015. First patients enrolled June 2015.

Diaphragm Function Assessment During Spontaneous Breathing Trial in Patients with Neuromuscular Diseases.

IntroductionThe optimal time to discontinue patients from mechanical ventilation is critical as premature discontinuation as well as delayed weaning can result in complications. The literature on diaphragm function assessment during the weaning process in the intriguing subpopulation of critically ill neuromuscular disease patients is lacking.MethodsPatients with neuromuscular diseases, on mechanical ventilation for more than 7 days, and who were ready for weaning were studied. During multiple T-piece trials over days, diaphragm function using ultrasound and diaphragm electrical activity (Edi peaks using NAVA catheter) was measured every 30 min till a successful 2 h weaning.ResultsA total of 18 patients were screened for eligibility over 5-month period and eight patients fulfilled the inclusion criteria. Sixty-three data points in these 8 subjects were available for analysis. A successful breathing trial was predicted by Edi reduction (1.22 μV for every 30 min increase in weaning duration; 0.69 μV for every day of weaning) and increase in diaphragm excursion (2.81 mm for every 30 min increase in weaning duration; 2.18 mm for every day of weaning).ConclusionThe Edi and diaphragm excursion changes can be used as additional objective tools in the decision-making of the weaning trials in neuromuscular disease.Electronic supplementary materialThe online version of this article (10.1007/s12028-020-01141-9) contains supplementary material, which is available to authorized users.

Pharmacological disinhibition enhances paced breathing following complete spinal cord injury in rats

Respiratory dysfunction is one of the most devastating and life-threatening deficits that occurs following cervical spinal cord injury (SCI). Assisted breathing with mechanical ventilators is a necessary part of care for many cervical injured individuals, but it is also associated with increased risk of secondary complications such as infection, muscle atrophy and maladaptive plasticity. Pre-clinical studies with epidural stimulation (EDS) have identified it as an alternative/additional method to support adequate lung ventilation without mechanical assistance. The full potential of EDS, however, may be limited by spinal inhibitory mechanisms within the injured spinal cord. The goal of the present work is to assess the potential improvement for EDS in combination with pharmacological disinhibition of spinal circuits following complete high cervical SCI. All experiments were performed in decerebrate, unanesthetized, non-paralyzed (n = 13) and paralyzed (n = 8) adult Sprague-Dawley rats 6 h following a complete C1 transection. The combination of high-frequency EDS (HF-EDS) at the C4 spinal segment with intrathecal delivery of GABA and glycine receptors antagonists (GABAzine and strychnine, respectively) resulted in significantly increased phrenic motor output, tidal volume and amplitude of diaphragm electrical activity compared to HF-EDS alone. Thus, it appears that spinal fast inhibitory mechanisms limit phrenic motor output and present a new neuropharmacological target to improve paced breathing in individuals with cervical SCI.

Inhibition of central activation of the diaphragm: a mechanism of weaning failure.

During a T-tube trial following disconnection of mechanical ventilation, patients failing the trial do not develop contractile diaphragmatic fatigue despite increases in inspiratory pressure output. Studies in volunteers, patients, and animals raise the possibility of spinal and supraspinal reflex mechanisms that inhibit central-neural output under loaded conditions. We hypothesized that diaphragmatic recruitment is submaximal at the end of a failed weaning trial despite concurrent respiratory distress. Tidal transdiaphragmatic pressure (ΔPdi) and electrical activity (ΔEAdi) were recorded with esophago-gastric catheters during a T-tube trial in 20 critically ill patients. During the T-tube trial, ∆EAdi was greater in weaning failure patients than in weaning success patients (P = 0.049). Despite increases in ΔPdi, from 18.1 ± 2.5 to 25.9 ± 3.7 cm H2O (P < 0.001), rate of transdiaphragmatic pressure development (from 22.6 ± 3.1 to 37.8 ± 6.7 cm H2O/s; P < 0.0004), and concurrent respiratory distress, ∆EAdi at the end of a failed T-tube trial was half of maximum, signifying inhibition of central neural output to the diaphragm. The increase in ΔPdi in the weaning failure group, while ∆EAdi remained constant, indicates unexpected improvement in diaphragmatic neuromuscular coupling (from 46.7 ± 6.5 to 57.8 ± 8.4 cm H2O/%; P = 0.006). Redistribution of neural output to the respiratory muscles characterized by a progressive increase in rib cage and accessory muscle contribution to tidal breathing and expiratory muscle recruitment contributed to enhanced coupling. In conclusion, diaphragmatic recruitment is submaximal at the end of a failed weaning trial despite concurrent respiratory distress. This finding signifies that reflex inhibition of central neural output to the diaphragm contributes to weaning failure.NEW & NOTEWORTHY Research into pathophysiology of failure to wean from mechanical ventilation has excluded several factors, including contractile fatigue, but the precise mechanism remains unknown. We recorded transdiaphragmatic pressure and diaphragmatic electrical activity in patients undergoing a T-tube trial. Diaphragmatic recruitment was submaximal at the end of a failed trial despite concurrent respiratory distress, signifying that inhibition of central neural output to the diaphragm is an important mechanism of weaning failure.