Randomized Clinical Study of Temporary Transvenous Phrenic Nerve Stimulation in Difficult-to-Wean Patients

Diaphragm neurostimulation in mechanical ventilation: current status and future prospects

INTRODUCTION

Diaphragm neurostimulation is a muscle stimulation technique that, through electrodes placed directly on or at the vicinity of the phrenic nerves, induces diaphragm contractions independently of the patient's cooperation. Recently, the technical development of temporary diaphragm neurostimulation devices has paved the way for a new era in the management of critically ill patients.

AREAS COVERED

In this review, we describe the latest technical developments in diaphragm neurostimulation and its physiological effects. We searched MEDLINE of experimental and clinical studies in English language published from database inception until 31 October 2024. We also discuss the advances in terms of patients centered outcomes and the key areas for improvement. Lastly, we introduce possible future directions and the novel improvements in patient care.

EXPERT OPINION

The research on diaphragm neurostimulation promise as an emerging intervention which addresses common complications associated with mechanical ventilation. Large-scale clinical trials are necessary to validate diaphragm neurostimulation efficacy and safety in humans, establish treatment protocols, and determine cost-effectiveness, all of which are essential for diaphragm neurostimulation to be widely accepted in clinical practice.

Monitoring and preserving diaphragmatic function in mechanical ventilation

PURPOSE OF REVIEW

This review summarizes the evidence on clinical outcomes related to diaphragm dysfunction, providing an overview on available monitoring tools and strategies for its prevention and treatment.

RECENT FINDINGS

Long-term adverse functional outcomes in intensive care survivors are well documented, especially in patients with prolonged mechanical ventilation. Because diaphragm weakness is highly prevalent and strongly associated with weaning failure, a link between diaphragm weakness and adverse functional outcomes is probable. Mechanisms of critical illness-associated diaphragm weakness are complex and include ventilator-related myotrauma through various pathways (i.e. over-assistance, under-assistance, eccentric, expiratory). Given this potential clinical impact, research on preventive and therapeutic strategies is growing including the development of ventilation strategies aiming at protecting both the lung and the diaphragm. Phrenic nerve stimulation and specific rehabilitation strategies also appear promising.

SUMMARY

Diaphragm dysfunction is associated with adverse clinical outcomes in ventilated patients; therefore, their inspiratory effort and function should be monitored. Whenever possible, and without compromising lung protection, moderate inspiratory effort should be targeted. Phrenic nerve stimulation and specific rehabilitation strategies are promising to prevent and treat diaphragm dysfunction, but further evidence is needed before widespread implementation.

Similar Weaning Success Rate with High-Intensity and Sham Inspiratory Muscle Training: A Randomized Controlled Trial (IMweanT)

Rationale: Inspiratory muscle training (IMT) improves respiratory muscle function in patients with weaning difficulties. IMT protocols involve performing daily sets of breaths against external loads. However, the impact of IMT on weaning outcomes while incorporating sham control interventions remains unclear. Objectives: To compare the effects of a high-intensity IMT (Hi-IMT) intervention with a sham low-intensity (Lo-IMT) control group on weaning outcomes and respiratory muscle and pulmonary function 28 days after inclusion in patients with weaning difficulties. Methods: Both groups underwent daily IMT sessions until successful weaning or a maximum of 28 days. The Hi-IMT group (n = 44; 61% male; aged 57 ± 15 yr) performed maximal inspirations initiated from residual volume against an external load representing 30-50% of maximal inspiratory pressure (PImax), and the control group (n = 46; 52% male; aged 60 ± 12 yr) performed maximal inspirations against a load ⩽10% PImax. Measurements and Main Results: Training adherence (completed/planned sessions) was comparable between the groups (Hi-IMT, 77 ± 20%; Lo-IMT, 72 ± 17%; P = 0.25). Weaning success (64% Hi-IMT and 76% Lo-IMT; P = 0.43) and weaning duration (Hi-IMT, 45 ± 48 d; Lo-IMT, 37 ± 26 d; P = 0.33) were similar between groups. Both groups similarly improved PImax (Hi-IMT, +15 cm H2O [95% confidence interval (CI), 9, 20]; Lo-IMT, +14 cm H2O [95% CI, 9, 19]; P = 0.72). FVC improved more in the Hi-IMT group than in the Lo-IMT group (Hi-IMT, +0.33 L [95% CI, 0.22, 0.43]; Lo-IMT, +0.16 L [95% CI, 0.07, 0.25]; P = 0.04). Conclusions: Both high-intensity IMT and sham low-intensity IMT, with high adherence to the protocol, resulted in similar weaning success rates and pronounced improvements in maximal inspiratory muscle strength. Clinical trial registered with www.clinicaltrials.gov (NCT03240263).

Advances in achieving lung and diaphragm-protective ventilation

PURPOSE OF REVIEW

Mechanical ventilation may have adverse effects on diaphragm and lung function. Lung- and diaphragm-protective ventilation is an approach that challenges the clinician to facilitate physiological respiratory efforts, while maintaining minimal lung stress and strain. Here, we discuss the latest advances in monitoring and interventions to achieve lung- and diaphragm protective ventilation.

RECENT FINDINGS

Noninvasive ventilator maneuvers (P0.1, airway occlusion pressure, pressure-muscle index) can accurately detect low and excessive respiratory efforts and high lung stress. Additional monitoring techniques include esophageal manometry, ultrasound, electrical activity of the diaphragm, and electrical impedance tomography. Recent trials demonstrate that a systematic approach to titrating inspiratory support and sedation facilitates lung- and diaphragm protective ventilation. Titration of positive-end expiratory pressure and, if available, veno-venous extracorporeal membrane oxygenation sweep gas flow may further modulate neural respiratory drive and effort to facilitate lung- and diaphragm protective ventilation.

SUMMARY

Achieving lung- and diaphragm-protective ventilation may require more than a single intervention; it demands a comprehensive understanding of the (neuro)physiology of breathing and mechanical ventilation, along with the application of a series of interventions under close monitoring. We suggest a bedside-approach to achieve lung- and diaphragm protective ventilation targets.

How to protect the diaphragm and the lung with diaphragm neurostimulation

PURPOSE OF REVIEW

In the current review, we aim to highlight the evolving evidence on using diaphragm neurostimulation to develop lung and diaphragm protective mechanical ventilation.

RECENT FINDINGS

Positive-pressure ventilation (PPV) causes stress and strain to the lungs which leads to ventilator-induced lung injury (VILI). In addition, PPV is frequently associated with sedatives that induce excessive diaphragm unloading which contributes to ventilator-induced diaphragmatic dysfunction (VIDD). The nonvolitional diaphragmatic contractions entrained by diaphragm neurostimulation generate negative pressure ventilation, which may be a beneficial alternative or complement to PPV. Although well established as a permanent treatment of central apnea syndromes, temporary diaphragm neurostimulation rapidly evolves to prevent and treat VILI and VIDD. Experimental and small clinical studies report comprehensive data showing that diaphragm neurostimulation has the potential to mitigate VIDD and to decrease the stress and strain applied to the lungs.

SUMMARY

Scientific interest in temporary diaphragm neurostimulation has dramatically evolved in the last few years. Despite a solid physiological rationale and promising preliminary findings confirming a beneficial effect on the diaphragm and lungs, more studies and further technological advances will be needed to establish optimal standardized settings and lead to clinical implementation and improved outcomes.

Randomized study of temporary diaphragm pacing for enhanced recovery after surgery in cardiac surgery patients at risk of prolonged mechanical ventilation

Objective

Prolonged mechanical ventilation after cardiac surgery significantly increases morbidity and mortality. The aim of this study is to establish the role of diaphragmatic pacing to decrease mechanical ventilation burden in high-risk patients undergoing cardiac surgery.

Methods

This is a prospective, randomized trial of temporary diaphragmatic pacing electrode use in patients undergoing cardiac surgery (NCT04899856). Prognostic enrichment strategy was used to identify patients at higher risk of prolonged mechanical ventilation by having inclusion criteria of prior open cardiac surgery, left ventricular ejection fraction less than 30%, history of stroke, intra-aortic balloon pump, or history of chronic obstructive pulmonary disease. Two electrodes were placed in each hemidiaphragm intraoperatively. On arrival to the intensive care unit, patients were randomized to immediate diaphragmatic pacing or standard of care.

Results

Forty patients received implants, with 19 in the treatment group and 21 in the standard of care group. Only 1 patient in the treatment group was on mechanical ventilation at 24 hours versus 4 patients in the standard of care group, resulting in a relative risk reduction of 71% being on mechanical ventilation at 24 hours postoperatively. Predictive enrichment strategy was used to identify patients most likely to respond to therapy of diaphragmatic pacing. In this analysis, median time on mechanical ventilation was 17.7 hours (interquartile range, 8.3-23.4) for the 15 patients in the standard of care group and 9.4 hours (interquartile range, 7.14-12.5) for the 13 patients in the treatment group, for an improvement of 8 hours with diaphragm pacing (P < .05).

Conclusions

Temporary diaphragmatic pacing improved weaning from mechanical ventilation by 8 hours with a significant reduction of prolonged mechanical ventilation. Multicenter randomized trials confirming diaphragmatic pacing as an Enhanced Recovery After Surgery tool to decrease mechanical ventilation may reduce length of stay, postoperative infections, and additive costs.

Transvenous phrenic nerve stimulation reduces diaphragm injury during controlled mechanical ventilation in a preclinical model of ARDS

Patients with acute respiratory distress syndrome (ARDS) require periods of deep sedation and mechanical ventilation, leading to diaphragm dysfunction. Our study seeks to determine whether the combination of temporary transvenous diaphragm neurostimulation (TTDN) and mechanical ventilation changes the degree of diaphragm injury and cytokines concentration in a preclinical ARDS model. Moderate ARDS was induced in pigs using oleic acid, followed by ventilation for 12 h post-injury with volume-control at 8 mL/kg, positive end-expiratory pressure (PEEP) 5 cmH2O, respiratory rate and [Formula: see text] set to achieve normal arterial blood gases. Two groups received TTDN: every second breath (MV + TTDN50%, n = 6) or every breath (MV + TTDN100%, n = 6). One group received ventilation only (MV, n = 6). Full-thickness diaphragm and quadricep muscle biopsies were taken at study end. Samples were fixed and stained with hematoxylin and eosin and a point-counting technique was applied to calculate abnormal muscle area fraction. Cytokine concentrations were measured in homogenized tissue using porcine-specific enzyme-linked immunosorbent assay (ELISA) and compared with serum samples. Percentage of abnormal diaphragm tissue was different between MV [8.1% (6.0-8.8)] versus MV + TTDN50% [3.4% (2.1-4.8)], P = 0.010 and MV versus MV + TTDN100% [3.1% (2.5-4.0)], P = 0.005. Percentage of abnormal quadriceps tissue was not different between groups. Cytokine concentration patterns in diaphragm samples were different between all groups (P < 0.001) and the interaction between TTDN application and resultant cytokine concentration pattern was significant (P = 0.025). TTDN, delivered in synchrony with mechanical ventilation, mitigated diaphragm injury, as evidenced by less abnormal tissue in the diaphragm samples, in pigs with oleic acid-induced ARDS and is an exciting tool for lung and diaphragm-protective ventilation.NEW & NOTEWORTHY This study adds to our understanding of applying transvenous diaphragm neurostimulation synchronously with mechanical ventilation by examining its effects on diaphragm muscle injury and cytokine concentration patterns in pigs with acute respiratory distress syndrome (ARDS). We observed that using this therapy for 12 h post lung injury mitigated ventilator-induced diaphragm injury and changed the pattern of cytokine concentration measured in diaphragm tissue. These findings suggest that transvenous diaphragm neurostimulation is an exciting tool for lung and diaphragm protective ventilation.

Respiratory muscle dysfunction in acute and chronic respiratory failure: how to diagnose and how to treat?

Assessing and treating respiratory muscle dysfunction is crucial for patients with both acute and chronic respiratory failure. Respiratory muscle dysfunction can contribute to the onset of respiratory failure and may also worsen due to interventions aimed at treatment. Evaluating respiratory muscle function is particularly valuable for diagnosing, phenotyping and assessing treatment efficacy in these patients. This review outlines established methods, such as measuring respiratory pressures, and explores novel techniques, including respiratory muscle neurophysiology assessments using electromyography and imaging with ultrasound.Additionally, we review various treatment strategies designed to support and alleviate the burden on overworked respiratory muscles or to enhance their capacity through training interventions. These strategies range from invasive and noninvasive mechanical ventilation approaches to specialised respiratory muscle training programmes. By summarising both established techniques and recent methodological advancements, this review aims to provide a comprehensive overview of the tools available in clinical practice for evaluating and treating respiratory muscle dysfunction. Our goal is to present a clear understanding of the current capabilities and limitations of these diagnostic and therapeutic approaches. Integrating advanced diagnostic methods and innovative treatment strategies should help improve patient management and outcomes. This comprehensive review serves as a resource for clinicians, equipping them with the necessary knowledge to effectively diagnose and treat respiratory muscle dysfunction in both acute and chronic respiratory failure scenarios.

Noninvasive Electromagnetic Phrenic Nerve Stimulation in Critically Ill Patients: A Feasibility Study

BACKGROUND

Electromagnetic stimulation of the phrenic nerve induces diaphragm contractions, but no coils for clinical use have been available. We recently demonstrated the feasibility of ventilation using bilateral transcutaneous noninvasive electromagnetic phrenic nerve stimulation (NEPNS) before surgery in lung-healthy patients with healthy weight in a dose-dependent manner.

RESEARCH QUESTION

Is NEPNS feasible in critically ill patients in an ICU setting?

STUDY DESIGN AND METHODS

This feasibility nonrandomized controlled study aimed to enroll patients within 36 h of intubation who were expected to remain ventilated for ≥ 72 h. The intervention group received 15-min bilateral transcutaneous NEPNS bid, whereas the control group received standard care. If sufficient, NEPNS was used without pressure support to ventilate the patient; pressure support was added if necessary to ventilate the patient adequately. The primary outcome was feasibility, measured as time to find the optimal stimulation position. Further end points were sessions performed according to the protocol or allowing a next-day catch-up session and tidal volume achieved with stimulation reaching only 3 to 6 mL/kg ideal body weight (IBW). A secondary end point was expiratory diaphragm thickness measured with ultrasound from days 1 to 10 (or extubation).

RESULTS

The revised European Union regulation mandated reapproval of medical devices, prematurely halting the study. Eleven patients (five in the intervention group, six in the control group) were enrolled. The median time to find an adequate stimulation position was 23 s (interquartile range, 12-62 s). The intervention bid was executed in 87% of patients, and 92% of patients including a next-day catch-up session. Ventilation with 3 to 6 mL/kg IBW was achieved in 732 of 1,701 stimulations (43.0%) with stimulation only and in 2,511 of 4,036 stimulations (62.2%) with additional pressure support. A decrease in diaphragm thickness was prevented by bilateral NEPNS (P = .034) until day 10.

INTERPRETATION

Bilateral transcutaneous NEPNS was feasible in the ICU setting with the potential benefit of preventing diaphragm atrophy during mechanical ventilation. NEPNS ventilation effectiveness needs further assessment.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT05238753; URL: www.

CLINICALTRIALS

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The ReInvigorate Study-phrenic nerve-to-diaphragm stimulation for weaning from mechanical ventilation: a protocol for a randomized pivotal clinical trial

BACKGROUND

In the United States in 2017, there were an estimated 903,745 hospitalizations involving mechanical ventilation (MV). Complications from ventilation can result in longer hospital stays, increased risk of disability, and increased healthcare costs. It has been hypothesized that electrically pacing the diaphragm by phrenic nerve stimulation during mechanical ventilation may minimize or reverse diaphragm dysfunction, resulting in faster weaning.

METHODS

The ReInvigorate Trial is a prospective, multicenter, randomized, controlled clinical trial evaluating the safety and efficacy of Stimdia's pdSTIM System for facilitating weaning from MV. The pdSTIM system employs percutaneously placed multipolar electrodes to stimulate the cervical phrenic nerves and activate contraction of the diaphragm bilaterally. Patients who were on mechanical ventilation for at least 96 h and who failed at least one weaning attempt were considered for enrollment in the study. The primary efficacy endpoint was the time to successful liberation from mechanical ventilation (treatment vs. control). Secondary endpoints will include the rapid shallow breathing index and other physiological and system characteristics. Safety will be summarized for both primary and additional analyses. All endpoints will be evaluated at 30 days or at the time of removal of mechanical ventilation, whichever is first.

DISCUSSION

This pivotal study is being conducted under an investigational device exception with the U.S. Food and Drug Administration. The technology being studied could provide a first-of-kind therapy for difficult-to-wean patients on mechanical ventilation in an intensive care unit setting.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT05998018 , registered August 2023.

Breath-by-breath comparison of a novel percutaneous phrenic nerve stimulation approach with mechanical ventilation in juvenile pigs: a pilot study

About one in three critically ill patients requires mechanical ventilation (MV). Prolonged MV, however, results in diaphragmatic weakness, which itself is associated with delayed weaning and increased mortality. Inducing active diaphragmatic contraction via electrical phrenic nerve stimulation (PNS) not only provides the potential to reduce diaphragmatic muscular atrophy but also generates physiological-like ventilation and therefore offers a promising alternative to MV. Reasons why PNS is not yet used in critical care medicine are high procedural invasiveness, insufficient evidence, and lack of side-by-side comparison to MV. This study aims to establish a minimal-invasive percutaneous, bilateral electrode placement approach for sole PNS breathing and thereby enable, for the first time, a breath-by-breath comparison to MV. Six juvenile German Landrace pigs received general anesthesia and orotracheal intubation. Following the novel ultrasound-guided, landmark-based, 4-step approach, two echogenic needles per phrenic nerve were successfully placed. Stimulation effectiveness was evaluated measuring tidal volume, diaphragmatic thickening and tomographic electrical impedance in a breath-by-breath comparison to MV. Following sufficient bilateral phrenic nerve stimulation in all pigs, PNS breaths showed a 2.2-fold increase in diaphragmatic thickening. It induced tidal volumes in the lung-protective range by negative pressure inspiration and improved dorso-caudal regional ventilation in contrast to MV. Our study demonstrated the feasibility of a novel ultrasound-guided, percutaneous phrenic nerve stimulation approach, which generated sufficient tidal volumes and showed more resemblance to physiological breathing than MV in a breath-by-breath comparison.

Critical illness-associated limb and diaphragmatic weakness

PURPOSE OF REVIEW

In the current review, we aim to highlight the evolving evidence on the diagnosis, prevention and treatment of critical illness weakness (CIW) and critical illness associated diaphragmatic weakness (CIDW).

RECENT FINDINGS

In the ICU, several risk factors can lead to CIW and CIDW. Recent evidence suggests that they have different pathophysiological mechanisms and impact on outcomes, although they share common risk factors and may overlap in several patients. Their diagnosis is challenging, because CIW diagnosis is primarily clinical and, therefore, difficult to obtain in the ICU population, and CIDW diagnosis is complex and not easily performed at the bedside. All of these issues lead to underdiagnosis of CIW and CIDW, which significantly increases the risk of complications and the impact on both short and long term outcomes. Moreover, recent studies have explored promising diagnostic techniques that are may be easily implemented in daily clinical practice. In addition, this review summarizes the latest research aimed at improving how to prevent and treat CIW and CIDW.

SUMMARY

This review aims to clarify some uncertain aspects and provide helpful information on developing monitoring techniques and therapeutic interventions for managing CIW and CIDW.

Diaphragm thickness modifications and associated factors during VA-ECMO for a cardiogenic shock: a cohort study

BACKGROUND

The incidence, causes and impact of diaphragm thickness evolution in veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for cardiogenic shock are unknown. Our study investigates its evolution during the first week of VA-ECMO and its relationship with sweep gas flow settings.

METHODS

We conducted a prospective monocentric observational study in a 12-bed ICU in France, enrolling patients on the day of the VA-ECMO implantation. The diaphragm thickness and the diaphragm thickening fraction (as index of contractile activity, dTF; dTF < 20% defined a low contractile activity) were daily measured for one week using ultrasound. Factors associated with diaphragm thickness evolution (categorized as increased, stable, or atrophic based on > 10% modification from baseline to the last measurement), early extubation role (< day4), and patients outcome at 60 days were investigated. Changes in diaphragm thickness, the primary endpoint, was analysed using a mixed-effect linear model (MLM).

RESULTS

Of the 29 included patients, seven (23%) presented diaphragm atrophy, 18 remained stable (60%) and 4 exhibited an increase (17%). None of the 13 early-extubated patients experienced diaphragm atrophy, while 7 (46%) presented a decrease when extubated later (p-value = 0.008). Diaphragm thickness changes were not associated with the dTF (p-value = 0.13) but with sweep gas flow (Beta = - 3; Confidence Interval at 95% (CI) [- 4.8; - 1.2]. p-value = 0.001) and pH (Beta = - 2; CI [- 2.9; - 1]. p-value < 0.001) in MLM. The dTF remained low (< 20%) in 20 patients (69%) at the study's end and was associated with sweep gas flow evolution in MLM (Beta = - 2.8; 95% CI [- 5.2; - 0.5], p-value = 0.017). Odds ratio of death at 60 days in case of diaphragm atrophy by day 7 was 8.50 ([1.4-74], p = 0.029).

CONCLUSION

In our study, diaphragm thickness evolution was frequent and not associated with the diaphragm thickening fraction. Diaphragm was preserved from atrophy in case of early extubation with ongoing VA-ECMO assistance. Metabolic disorders resulting from organ failures and sweep gas flow were linked with diaphragm thickness evolution. Preserved diaphragm thickness in VA-ECMO survivors emphasizes the importance of diaphragm-protective strategies, including meticulous sweep gas flow titration.

Rapid review of ventilator-induced diaphragm dysfunction

Ventilator-induced diaphragm dysfunction is gaining increased recognition. Evidence of diaphragm weakness can manifest within 12 h to a few days after the initiation of mechanical ventilation. Various noninvasive and invasive methods have been developed to assess diaphragm function. The implementation of diaphragm-protective ventilation strategies is crucial for preventing diaphragm injuries. Furthermore, diaphragm neurostimulation emerges as a promising and novel treatment option. In this rapid review, our objective is to discuss the current understanding of ventilator-induced diaphragm dysfunction, diagnostic approaches, and updates on strategies for prevention and management.

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

BACKGROUND

Ventilator-induced diaphragm dysfunction occurs rapidly following the onset of mechanical ventilation and has significant clinical consequences. Phrenic nerve stimulation has shown promise in maintaining diaphragm function by inducing diaphragm contractions. Non-invasive stimulation is an attractive option as it minimizes the procedural risks associated with invasive approaches. However, this method is limited by sensitivity to electrode position and inter-individual variability in stimulation thresholds. This makes clinical application challenging due to potentially time-consuming calibration processes to achieve reliable stimulation.

METHODS

We applied non-invasive electrical stimulation to the phrenic nerve in the neck in healthy volunteers. A closed-loop system recorded the respiratory flow produced by stimulation and automatically adjusted the electrode position and stimulation amplitude based on the respiratory response. By iterating over electrodes, the optimal electrode was selected. A binary search method over stimulation amplitudes was then employed to determine an individualized stimulation threshold. Pulse trains above this threshold were delivered to produce diaphragm contraction.

RESULTS

Nine healthy volunteers were recruited. Mean threshold stimulation amplitude was 36.17 ± 14.34 mA (range 19.38-59.06 mA). The threshold amplitude for reliable nerve capture was moderately correlated with BMI (Pearson's r = 0.66, p = 0.049). Repeating threshold measurements within subjects demonstrated low intra-subject variability of 2.15 ± 1.61 mA between maximum and minimum thresholds on repeated trials. Bilateral stimulation with individually optimized parameters generated reliable diaphragm contraction, resulting in significant inhaled volumes following stimulation.

CONCLUSION

We demonstrate the feasibility of a system for automatic optimization of electrode position and stimulation parameters using a closed-loop system. This opens the possibility of easily deployable individualized stimulation in the intensive care setting to reduce ventilator-induced diaphragm dysfunction.

An Initial Investigation of Diaphragm Neurostimulation in Patients with Acute Respiratory Distress Syndrome

BACKGROUND

Lung protective ventilation aims at limiting lung stress and strain. By reducing the amount of pressure transmitted by the ventilator into the lungs, diaphragm neurostimulation offers a promising approach to minimize ventilator-induced lung injury. This study investigates the physiologic effects of diaphragm neurostimulation in acute respiratory distress syndrome (ARDS) patients. The hypothesis was that diaphragm neurostimulation would improve oxygenation, would limit the distending pressures of the lungs, and would improve cardiac output.

METHODS

Patients with moderate ARDS were included after 48 h of invasive mechanical ventilation and had a left subclavian catheter placed to deliver bilateral transvenous phrenic nerve stimulation. Two 60-min volume-controlled mechanical ventilation (control) sessions were interspersed by two 60-min diaphragm neurostimulation sessions delivered continually, in synchrony with the ventilator. Gas exchange, lung mechanics, chest electrical impedance tomography, and cardiac index were continuously monitored and compared across four sessions. The primary endpoint was the Pao2/fraction of inspired oxygen (Fio2) ratio at the end of each session, and the secondary endpoints were lung mechanics and hemodynamics.

RESULTS

Thirteen patients were enrolled but the catheter could not be inserted in one, leaving 12 patients for analysis. All sessions were conducted without interruption and well tolerated. The Pao2/Fio2 ratio did not change during the four sessions. Median (interquartile range) plateau pressure was 23 (20 to 31) cm H2O and 21 (17 to 25) cm H2O, driving pressure was 14 (12 to 18) cm H2O and 11 (10 to 13) cm H2O, and end-inspiratory transpulmonary pressure was 9 (5 to 11) cm H2O and 7 (4 to 11) cm H2O during mechanical ventilation alone and during mechanical ventilation + neurostimulation session, respectively. The dorsal/ventral ventilation surface ratio was 0.70 (0.54 to 0.91) when on mechanical ventilation and 1.20 (0.76 to 1.33) during the mechanical ventilation + neurostimulation session. The cardiac index was 2.7 (2.3 to 3.5) l · min-1 · m-2 on mechanical ventilation and 3.0 (2.4 to 3.9) l · min-1 · m-2 on mechanical ventilation + neurostimulation.

CONCLUSIONS

This proof-of-concept study showed the feasibility of short-term diaphragm neurostimulation in conjunction with mechanical ventilation in ARDS patients. Diaphragm neurostimulation was associated with positive effects on lung mechanics and on hemodynamics.

EDITOR’S PERSPECTIVE

[Electromagnetic stimulation in diaphragm dysfunction: repetitive peripheral magnetic stimulation as a method of choice during the rehabilitation period after stroke. (Literature review)]

Diaphragm dysfunction develops in central nervous system damage, chest injuries, complications of cardiac surgery, long-term artificial lung ventilation, respiratory diseases. Anatomical morphological features of phrenic nerves allow to effectively use electromagnetic stimulation methods for functional recovery of the diaphragm in different pathological conditions. Invasive and non-invasive, electric and magnetic methods of stimulation are used depending on the severity of manifestations of the diaphragm dysfunction and its genesis.

OBJECTIVE

To perform a review and comparison of modern methods of electromagnetic stimulation of the diaphragm; to determine the role of repetitive peripheral magnetic stimulation (rPMS) in the diaphragm dysfunction as a result of stroke.

MATERIAL AND METHODS

An analysis of publications from the Pubmed and Elibrary databases for 2008-2024 years was conducted. The search was done by the following keywords: diaphragm dysfunction, repetitive peripheral magnetic stimulation of phrenic nerve, stroke, hemiparesis.

RESULTS

There is a real possibility of effective diaphragm stimulation for recovery of its function due to the innervation of the diaphragm strictly by the phrenic nerves, their large diameter, presence of myelinated fibers as well as anatomical location of the phrenic nerves. Direct electric stimulation of the phrenic nerve is usually applied in the case of long-term continuous support of respiratory function. Non-invasive techniques of electric or magnetic stimulation of the phrenic nerve or directly of the diaphragmatic muscle are used in the case of temporary respiratory support or recovery of diaphragm function. The motor neurons of the brain and peripheral nerves are activated, thus a peak strength of the variable magnetic field usually reachs 1-2 T in rPMS. Application of rPMS affects the efferent nerve fibers, causing muscle contractions, and activates sensory afferent fibers, creating a stimulating effect on the superjacent nervous structures. It is advisable to use rPMS of the phrenic nerve in the cervical segment or rPMS of one of the segments of the diaphragmatic muscle in the case of unilateral diaphragm lesion during the recovery period after stroke. It is important to consider the frequency of exposure in the 10-30 Hz range, the closest location of the coil to the stimulation area, the choice of the coil shape depending on the localization when adjusting parameters of rPMS.

CONCLUSION

The use of rPMS of the phrenic nerve and diaphragm allows to preserve and recover motor and contractile functions of the diaphragm in different pathological conditions, including its unilateral lesion as a result of stroke. The method of rPMS of the phrenic nerves has a number of advantages over electric stimulation and repetitive transcranial magnetic stimulation, since it allows to achieve an effective motor response with less intensity of exposure, is painless and non-contact, better tolerated by patients.

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

Side effects of mechanical ventilation, such as ventilator-induced diaphragmatic dysfunction (VIDD) and ventilator-induced lung injury (VILI), occur frequently in critically ill patients. Phrenic nerve stimulation (PNS) has been a valuable tool for diagnosing VIDD by assessing respiratory muscle strength in response to magnetic PNS. The detection of pathophysiologically reduced respiratory muscle strength is correlated with weaning failure, longer mechanical ventilation time, and mortality. Non-invasive electromagnetic PNS designed for diagnostic use is a reference technique that allows clinicians to measure transdiaphragm pressure as a surrogate parameter for diaphragm strength and functionality. This helps to identify diaphragm-related issues that may impact weaning readiness and respiratory support requirements, although lack of lung volume measurement poses a challenge to interpretation. In recent years, therapeutic PNS has been demonstrated as feasible and safe in lung-healthy and critically ill patients. Effects on critically ill patients' VIDD or diaphragm atrophy outcomes are the subject of ongoing research. The currently investigated application forms are diverse and vary from invasive to non-invasive and from electrical to (electro)magnetic PNS, with most data available for electrical stimulation. Increased inspiratory muscle strength and improved diaphragm activity (e.g., excursion, thickening fraction, and thickness) indicate the potential of the technique for beneficial effects on clinical outcomes as it has been successfully used in spinal cord injured patients. Concerning the potential for electrophrenic respiration, the data obtained with non-invasive electromagnetic PNS suggest that the induced diaphragmatic contractions result in airway pressure swings and tidal volumes remaining within the thresholds of lung-protective mechanical ventilation. PNS holds significant promise as a therapeutic intervention in the critical care setting, with potential applications for ameliorating VIDD and the ability for diaphragm training in a safe lung-protective spectrum, thereby possibly reducing the risk of VILI indirectly. Outcomes of such diaphragm training have not been sufficiently explored to date but offer the perspective for enhanced patient care and reducing weaning failure. Future research might focus on using PNS in combination with invasive and non-invasive assisted ventilation with automatic synchronisation and the modulation of PNS with spontaneous breathing efforts. Explorative approaches may investigate the feasibility of long-term electrophrenic ventilation as an alternative to positive pressure-based ventilation.

Outcomes in critically ill patients after diaphragmatic stimulation on ventilator-induced diaphragmatic dysfunction: a systematic review

INTRODUCTION

Mechanical ventilation (MV) is a lifesaving procedure for critically ill patients. Diaphragm activation and stimulation may counteract side effects, such as ventilator-induced diaphragm dysfunction (VIDD). The effects of stimulation on diaphragm atrophy and patient outcomes are reported in this systematic review.

EVIDENCE ACQUISITION

Studies investigating diaphragmatic stimulation versus standard of care in critically ill patients and evaluating clinical outcomes were extracted from a Medline database last on January 23, 2023, after registration in Prospero (CRD42021259353). Selected studies included the investigation of diaphragmatic stimulation versus standard of care in critically ill patients, an evaluation of the clinical outcomes. These included muscle atrophy, VIDD, weaning failure, mortality, quality of life, ventilation time, diaphragmatic function, length of stay in the Intensive Care Unit (ICU), and length of hospital stay. All articles were independently evaluated by two reviewers according to their abstract and title and, secondly, a full texts evaluation by two independent reviewers was performed. To resolve diverging evaluations, a third reviewer was consulted to reach a final decision. Data were extracted by the reviewers following the Oxford 2011 levels of evidence guidelines and summarized accordingly.

EVIDENCE SYNTHESIS

Seven studies were extracted and descriptively synthesized, since a metanalysis was not feasible. Patients undergoing diaphragm stimulation had moderate evidence of higher maximal inspiratory pressure (MIP), less atrophy, less mitochondrial respiratory dysfunction, less oxidative stress, less molecular atrophy, shorter MV time, shorter ICU length of stay, longer survival, and better SF-36 scores than control.

CONCLUSIONS

Evidence of the molecular and histological benefits of diaphragmatic stimulation is limited. The results indicate positive clinical effects of diaphragm activation with a moderate level of evidence for MIP and a low level of evidence for other outcomes. Diaphragm activation could be a therapeutic solution to avoid diaphragm atrophy, accelerate weaning, shorten MV time, and counteract VIDD; however, better-powered studies are needed to increase the level of evidence.

Phrenic Nerve Stimulation for Acute Respiratory Failure

Diaphragm inactivity during invasive mechanical ventilation leads to diaphragm atrophy and weakness, hemodynamic instability, and ventilatory heterogeneity. Absent respiratory drive and effort can, therefore, worsen injury to both lung and diaphragm and is a major cause of failure to wean. Phrenic nerve stimulation (PNS) can maintain controlled levels of diaphragm activity independent of intrinsic drive and as such may offer a promising approach to achieving lung and diaphragm protective ventilatory targets. Whereas PNS has an established role in the management of chronic respiratory failure, there is emerging interest in how its multisystem putative benefits may be temporarily harnessed in the management of invasively ventilated patients with acute respiratory failure.

Sonometric assessment of cough predicts extubation failure: SonoWean-a proof-of-concept study

BACKGROUND

Extubation failure is associated with increased mortality. Cough ineffectiveness may be associated with extubation failure, but its quantification for patients undergoing weaning from invasive mechanical ventilation (IMV) remains challenging.

METHODS

Patients under IMV for more than 24 h completing a successful spontaneous T-tube breathing trial (SBT) were included. At the end of the SBT, we performed quantitative sonometric assessment of three successive coughing efforts using a sonometer. The mean of the 3-cough volume in decibels was named Sonoscore.

RESULTS

During a 1-year period, 106 patients were included. Median age was 65 [51-75] years, mainly men (60%). Main reasons for IMV were acute respiratory failure (43%), coma (25%) and shock (17%). Median duration of IMV at enrollment was 4 [3-7] days. Extubation failure occurred in 15 (14%) patients. Baseline characteristics were similar between success and failure extubation groups, except percentage of simple weaning which was lower and MV duration which was longer in extubation failure patients. Sonoscore was significantly lower in patients who failed extubation (58 [52-64] vs. 75 [70-78] dB, P < 0.001). After adjustment on MV duration and comorbidities, Sonoscore remained associated with extubation failure. Sonoscore was predictive of extubation failure with an area under the ROC curve of 0.91 (IC95% [0.83-0.99], P < 0.001). A threshold of Sonoscore < 67.1 dB predicted extubation failure with a sensitivity of 0.93 IC95% [0.70-0.99] and a specificity of 0.82 IC95% [0.73-0.90].

CONCLUSION

Sonometric assessment of cough strength might be helpful to identify patients at risk of extubation failure in patients undergoing IMV.

Transcutaneous electrical diaphragmatic stimulation in mechanically ventilated patients: a randomised study

BACKGROUND

Few specific methods are available to reduce the risk of diaphragmatic dysfunction for patients under mechanical ventilation. The number of studies involving transcutaneous electrical stimulation of the diaphragm (TEDS) is increasing but none report results for diaphragmatic measurements, and they lack power. We hypothesised that the use of TEDS would decrease diaphragmatic dysfunction and improve respiratory muscle strength in patients in ICU.

METHODS

We conducted a controlled trial to assess the impact of daily active electrical stimulation versus sham stimulation on the prevention of diaphragm dysfunction during the weaning process from mechanical ventilation. The evaluation was based on ultrasound measurements of diaphragm thickening fraction during spontaneous breathing trials. We also measured maximal inspiratory muscle pressure (MIP), peak cough flow (PEF) and extubation failure.

RESULTS

Sixty-six patients were included and randomised using a 1:1 ratio. The mean number of days of mechanical ventilation was 10 ± 6.8. Diaphragm thickening fraction was > 30% at the SBT for 67% of participants in the TEDS group and 54% of the Sham group (OR1.55, 95% CI 0.47-5.1; p = 0.47). MIP and PEF were similar in the TEDS and Sham groups (respectively 35.5 ± 11.9 vs 29.7 ± 11.7 cmH20; p = 0.469 and 83.2 ± 39.5 vs. 75.3 ± 34.08 L/min; p = 0.83). Rate of extubation failure was not different between groups.

CONCLUSION

TEDS did not prevent diaphragm dysfunction or improve inspiratory muscle strength in mechanically ventilated patients.

TRIAL REGISTRATION

Prospectively registered on the 20th November 2019 on ClinicalTrials.gov Identifier NCT04171024.

Managing respiratory muscle weakness during weaning from invasive ventilation

Weaning is a critical stage of an intensive care unit (ICU) stay, in which the respiratory muscles play a major role. Weakness of the respiratory muscles, which is associated with significant morbidity in the ICU, is not limited to atrophy and subsequent dysfunction of the diaphragm; the extradiaphragmatic inspiratory and expiratory muscles also play important parts. In addition to the well-established deleterious effect of mechanical ventilation on the respiratory muscles, other risk factors such as sepsis may be involved. Weakness of the respiratory muscles can be suspected visually in a patient with paradoxical movement of the abdominal compartment. Measurement of maximal inspiratory pressure is the simplest way to assess respiratory muscle function, but it does not specifically take the diaphragm into account. A cut-off value of -30 cmH2O could identify patients at risk for prolonged ventilatory weaning; however, ultrasound may be better for assessing respiratory muscle function in the ICU. Although diaphragm dysfunction has been associated with weaning failure, this diagnosis should not discourage clinicians from performing spontaneous breathing trials and considering extubation. Recent therapeutic developments aimed at preserving or restoring respiratory muscle function are promising.

Diaphragm Neurostimulation Assisted Ventilation in Critically Ill Patients

Diaphragm neurostimulation consists of placing electrodes directly on or in proximity to the phrenic nerve(s) to elicit diaphragmatic contractions. Since its initial description in the 18th century, indications have shifted from cardiopulmonary resuscitation to long-term ventilatory support. Recently, the technical development of devices for temporary diaphragm neurostimulation has opened up the possibility of a new era for the management of mechanically ventilated patients. Combining positive pressure ventilation with diaphragm neurostimulation offers a potentially promising new approach to the delivery of mechanical ventilation which may benefit multiple organ systems. Maintaining diaphragm contractions during ventilation may attenuate diaphragm atrophy and accelerate weaning from mechanical ventilation. Preventing atelectasis and preserving lung volume can reduce lung stress and strain and improve homogeneity of ventilation, potentially mitigating ventilator-induced lung injury. Furthermore, restoring the thoracoabdominal pressure gradient generated by diaphragm contractions may attenuate the drop in cardiac output induced by positive pressure ventilation. Experimental evidence suggests diaphragm neurostimulation may prevent neuroinflammation associated with mechanical ventilation. This review describes the historical development and evolving approaches to diaphragm neurostimulation during mechanical ventilation and surveys the potential mechanisms of benefit. The review proposes a research agenda and offers perspectives for the future of diaphragm neurostimulation assisted mechanical ventilation for critically ill patients.

Safety and Feasibility of Noninvasive Electromagnetic Stimulation of the Phrenic Nerves

BACKGROUND

Mechanical ventilation is widely used in ICU patients as a lifesaving intervention. Diaphragmatic atrophy and thinning occur from lack of contractions of the diaphragm during mechanical ventilation. It may prolong weaning and increase the risk of respiratory complications. Noninvasive electromagnetic stimulation of the phrenic nerves may ameliorate the atrophy seen with ventilation. The objective of this study was to show that noninvasive repetitive electromagnetic stimulation is safe, feasible, and effective to stimulate the phrenic nerves in both awake individuals and anesthetized patients.

METHODS

A single-center study with 10 subjects overall, 5 awake volunteers and 5 anesthetized subjects. We used a prototype electromagnetic, noninvasive, simultaneous bilateral phrenic nerve stimulation device in both groups. In the awake volunteers, we assessed time-to-first capture of the phrenic nerves and safety measures, such as pain, discomfort, dental paresthesia, and skin irritation. In the anesthetized subjects, time-to-first capture as well as tidal volumes and airway pressures at 20%, 30%, and 40% stimulation intensity were assessed.

RESULTS

Diaphragmatic capture was achieved in all the subjects within a median (range) of 1 min (1 min to 9 min 21 s) for the awake subjects and 30 s (20 s to 1 min 15 s) for the anesthetized subjects. There were no adverse or severe adverse events in either group, nor any dental paresthesia, skin irritation, or subjective pain in the stimulated area. Tidal volumes increased in all the subjects in response to simultaneous bilateral phrenic nerve stimulation and increased gradually with increasing stimulation intensity. Airway pressures corresponded to spontaneous breathing of ∼2 cm H2O.

CONCLUSIONS

Noninvasive phrenic nerve stimulation can be safely performed in awake and anesthetized individuals. It was feasible and effective in stimulating the diaphragm by induction of physiologic and scalable tidal volumes with minimum positive airway pressures.

Temporary phrenic nerve stimulated patients: What is the role of ultrasound examination?

BACKGROUND

Prolonged mechanical ventilation caused by ventilator-induced diaphragm dysfunction (VIDD) is a serious problem in critically ill patients. Identification of patients who will have difficulty weaning from ventilation along with attempts to reduce total time on mechanical ventilation is some of the aims of intensive care medicine.

OBSERVATIONS

This article briefly summarizes current options for temporary phrenic nerve stimulation therapy in an effort to keep the diaphragm active as direct prevention and treatment of ventilator-associated diaphragmatic dysfunction in patients on mechanical ventilation. The results of feasibility studies using different approaches are promising but so far, the clinical relevance is low. One important question is which tool would reliably identify early signs of diaphragmatic dysfunction and also be useful in guiding therapy. The authors present a brief overview of the current options considering the advantages and disadvantages of the available examination modalities. Despite the fact that current data point out some limitations of ultrasound examination, we believe that it still has a unique position in the bedside examination of critically ill patients on mechanical ventilation.

CONCLUSION

Temporary phrenic nerve stimulation, regardless of the specific approach used, has the potential to directly treat or reverse VIDD, and ultrasound examination plays an important role in the comprehensive care of critically ill patients.

Feasibility of transesophageal phrenic nerve stimulation

BACKGROUND

Every year, more than 2.5 million critically ill patients in the ICU are dependent on mechanical ventilation. The positive pressure in the lungs generated by the ventilator keeps the diaphragm passive, which can lead to a loss of myofibers within a short time. To prevent ventilator-induced diaphragmatic dysfunction (VIDD), phrenic nerve stimulation may be used.

OBJECTIVE

The goal of this study is to show the feasibility of transesophageal phrenic nerve stimulation (TEPNS). We hypothesize that selective phrenic nerve stimulation can efficiently activate the diaphragm with reduced co-stimulations.

METHODS

An in vitro study in saline solution combined with anatomical findings was performed to investigate relevant stimulation parameters such as inter-electrode spacing, range to target site, or omnidirectional vs. sectioned electrodes. Subsequently, dedicated esophageal electrodes were inserted into a pig and single stimulation pulses were delivered simultaneously with mechanical ventilation. Various stimulation sites and response parameters such as transdiaphragmatic pressure or airway flow were analyzed to establish an appropriate stimulation setting.

RESULTS

Phrenic nerve stimulation with esophageal electrodes has been demonstrated. With a current amplitude of 40 mA, similar response figures of the diaphragm activation as compared to conventional stimulation with needle electrodes at 10mA were observed. Directed electrodes best aligned with the phrenic nerve resulted in up to 16.9 % higher amplitude at the target site in vitro and up to 6 cmH20 higher transdiaphragmatic pressure in vivo as compared to omnidirectional electrodes. The activation efficiency was more sensitive to the stimulation level inside the esophagus than to the inter-electrode spacing. Most effective and selective stimulation was achieved at the level of rib 1 using sectioned electrodes 40 mm apart.

CONCLUSION

Directed transesophageal phrenic nerve stimulation with single stimuli enabled diaphragm activation. In the future, this method might keep the diaphragm active during, and even support, artificial ventilation. Meanwhile, dedicated sectioned electrodes could be integrated into gastric feeding tubes.

Non-invasive phrenic nerve stimulation to avoid ventilator-induced diaphragm dysfunction in critical care

BACKGROUND

Diaphragm muscle atrophy during mechanical ventilation begins within 24 h and progresses rapidly with significant clinical consequences. Electrical stimulation of the phrenic nerves using invasive electrodes has shown promise in maintaining diaphragm condition by inducing intermittent diaphragm muscle contraction. However, the widespread application of these methods may be limited by their risks as well as the technical and environmental requirements of placement and care. Non-invasive stimulation would offer a valuable alternative method to maintain diaphragm health while overcoming these limitations.

METHODS

We applied non-invasive electrical stimulation to the phrenic nerve in the neck in healthy volunteers. Respiratory pressure and flow, diaphragm electromyography and mechanomyography, and ultrasound visualization were used to assess the diaphragmatic response to stimulation. The electrode positions and stimulation parameters were systematically varied in order to investigate the influence of these parameters on the ability to induce diaphragm contraction with non-invasive stimulation.

RESULTS

We demonstrate that non-invasive capture of the phrenic nerve is feasible using surface electrodes without the application of pressure, and characterize the stimulation parameters required to achieve therapeutic diaphragm contractions in healthy volunteers. We show that an optimal electrode position for phrenic nerve capture can be identified and that this position does not vary as head orientation is changed. The stimulation parameters required to produce a diaphragm response at this site are characterized and we show that burst stimulation above the activation threshold reliably produces diaphragm contractions sufficient to drive an inspired volume of over 600 ml, indicating the ability to produce significant diaphragmatic work using non-invasive stimulation.

CONCLUSION

This opens the possibility of non-invasive systems, requiring minimal specialist skills to set up, for maintaining diaphragm function in the intensive care setting.

Expert consensus on liver transplantation perioperative evaluation and rehabilitation for acute-on-chronic liver failure

Acute-on-chronic liver failure (ACLF) can be cured by liver transplantation; however, perioperative complications still affect posttransplant outcomes. In recent years, early rehabilitation for critical illness, liver disease, and surgery have significantly improved organ reserve function, surgery tolerance, and postoperative quality of life. They could also be applied in the perioperative period of liver transplantation in patients with ACLF. Therefore, the Transplantation Immunology Committee of Branch of Organ Transplantation Physician of Chinese Medical Doctor Association, the Organ Transplant Committee of China Association Rehabilitation Medicine, and the Guangdong Medical Doctor Association of Organ Transplantation conducted a comprehensive review of rehabilitation in end-stage liver disease, critical illness and surgical patients by summarizing current evidence and best clinical practices and proposed a practice consensus on evaluation of cardiopulmonary and physical function, rehabilitation or physiotherapies, as well as the safety concerns in perioperative liver transplant recipients. It will be a valuable resource for hepatologists, transplant surgeons, and intensivists as they care for ACLF patients during transplantation.

Inspiratory response and side-effects to rapid bilateral magnetic phrenic nerve stimulation using differently shaped coils: implications for stimulation-assisted mechanical ventilation

BACKGROUND

Rapid magnetic stimulation (RMS) of the phrenic nerves may serve to attenuate diaphragm atrophy during mechanical ventilation. With different coil shapes and stimulation location, inspiratory responses and side-effects may differ. This study aimed to compare the inspiratory and sensory responses of three different RMS-coils either used bilaterally on the neck or on the chest, and to determine if ventilation over 10 min can be achieved without muscle fatigue and coils overheating.

METHODS

Healthy participants underwent bilateral anterior 1-s RMS on the neck (RMS_BAMPS) (N = 14) with three different pairs of magnetic coils (parabolic, D-shape, butterfly) at 15, 20, 25 and 30 Hz stimulator-frequency and 20% stimulator-output with + 10% increments. The D-shape coil with individual optimal stimulation settings was then used to ventilate participants (N = 11) for up to 10 min. Anterior RMS on the chest (RMS_aMS) (N = 8) was conducted on an optional visit. Airflow was assessed via pneumotach and transdiaphragmatic pressure via oesophageal and gastric balloon catheters. Perception of air hunger, pain, discomfort and paresthesia were measured with a numerical scale.

RESULTS

Inspiration was induced via RMS_BAMPS in 86% of participants with all coils and via RMS_aMS in only one participant with the parabolic coil. All coils produced similar inspiratory and sensory responses during RMS_BAMPS with the butterfly coil needing higher stimulator-output, which resulted in significantly larger discomfort ratings at maximal inspiratory responses. Ten of 11 participants achieved 10 min of ventilation without decreases in minute ventilation (15.7 ± 4.6 L/min).

CONCLUSIONS

RMS_BAMPS was more effective than RMS_aMS, and could temporarily ventilate humans seemingly without development of muscular fatigue. Trial registration This study was registered on clinicaltrials.gov (NCT04176744).

The physiological underpinnings of life-saving respiratory support

Treatment of respiratory failure has improved dramatically since the polio epidemic in the 1950s with the use of invasive techniques for respiratory support: mechanical ventilation and extracorporeal respiratory support. However, respiratory support is only a supportive therapy, designed to "buy time" while the disease causing respiratory failure abates. It ensures viable gas exchange and prevents cardiorespiratory collapse in the context of excessive loads. Because the use of invasive modalities of respiratory support is also associated with substantial harm, it remains the responsibility of the clinician to minimize such hazards. Direct iatrogenic consequences of mechanical ventilation include the risk to the lung (ventilator-induced lung injury) and the diaphragm (ventilator-induced diaphragm dysfunction and other forms of myotrauma). Adverse consequences on hemodynamics can also be significant. Indirect consequences (e.g., immobilization, sleep disruption) can have devastating long-term effects. Increasing awareness and understanding of these mechanisms of injury has led to a change in the philosophy of care with a shift from aiming to normalize gases toward minimizing harm. Lung (and more recently also diaphragm) protective ventilation strategies include the use of extracorporeal respiratory support when the risk of ventilation becomes excessive. This review provides an overview of the historical background of respiratory support, pathophysiology of respiratory failure and rationale for respiratory support, iatrogenic consequences from mechanical ventilation, specifics of the implementation of mechanical ventilation, and role of extracorporeal respiratory support. It highlights the need for appropriate monitoring to estimate risks and to individualize ventilation and sedation to provide safe respiratory support to each patient.