Observational study of early diaphragm pacing in cervical spinal cord injured patients to decrease mechanical ventilation during the COVID-19 pandemic.

BACKGROUND: Decreasing the burden of mechanical ventilation for spinal cord injuries was never more relevant than during the COVID-19 pandemic. Data have shown diaphragm pacing can replace mechanical ventilation, decrease wean times, improve respiratory mechanics, and decrease hospital costs for patients with spinal cord injuries. This is the largest report of diaphragm pacing during the pandemic. METHODS: This is a retrospective analysis of prospective Institutional Review Board approved databases of nonrandomized interventional experience at a single institution. Subgroup analysis limited to traumatic cervical spinal cord injuries that were implanted laparoscopically with diaphragm electrodes within 30 days of injury. RESULTS: For the study group of early implanted traumatic cervical spinal cord injuries, 13 subjects were identified from a database of 197 diaphragm pacing implantations from January 1, 2020, to December 31, 2022, for all indications. All subjects were male with an average age of 49.3 years (range, 17-70). Injury mechanisms included falls (6), motor vehicle accident (4), gunshot wound (2), and diving (1). Time from injury to diaphragm pacing averaged 11 days (range, 3-22). Two patients are deceased and neither weaned from mechanical ventilation. Nine of the remaining 11 patients weaned from mechanical ventilation. Four patients never had a tracheostomy and 3 additional patients had tracheostomy decannulation. Three of these high-risk pulmonary compromised patients survived COVID-19 infections utilizing diaphragm pacing. CONCLUSION: Diaphragm pacing successfully weaned from mechanical ventilation 82% of patients surviving past 90 days. Forty-four percent of this group never underwent a tracheostomy. Only 22% of the weaned group required long term tracheostomies. Early diaphragm pacing for spinal cord injuries decreases mechanical ventilation usage and tracheostomy need which allows for earlier placement for rehabilitation.

Diaphragm pacing in spinal cord injury can significantly decrease mechanical ventilation in multicenter prospective evaluation.

BACKGROUND: Cervical spinal cord injury (SCI) can lead to dependence on mechanical ventilation (MV) with significant morbidity and mortality. The diaphragm pacing system (DPS) was developed as an alternative to MV. METHODS: We conducted a prospective single-arm study of DPS in MV-dependent patients with high SCI and intact phrenic nerves. Following device acclimation, pacing effectiveness to provide ventilation was evaluated. The primary endpoint was the number who could use DPS to breathe for 4 continuous hours without MV. Secondary endpoints included the number of patients that could use DPS 24 h/day free of MV and the ability of DPS to maintain clinically acceptable tidal volume (Vt). In addition, we conducted a meta-analysis that included the prospective study along with data from four recently published studies to evaluate DPS hourly use. RESULTS: Fifty-three patients were implanted in the prospective study. Most were male (77.4%) with a median time from injury to treatment of 28.3 (IQR: 12.1, 83.3) months. Four- and 24-h use occurred in 96.2% (95% CI: 87.0%, 99.5%) and 58.5% (95% CI: 44.1%, 74.9%), respectively. Four and 24-h results in the meta-analysis cohort (n = 196) exhibited similar results 92.2% (95% CI: 82.6%, 96.7%) and 52.7% (95% CI: 36.2%, 68.6%) using DPS for 4 and 24 h, respectively. DPS use significantly exceeded the calculated basal tidal volume requirements by a mean of 48.4% (95% CI: 37.0, 59.9%; p < 0.001). CONCLUSIONS: This study demonstrates that in most ventilator-dependent patients, diaphragm pacing can effectively supplement or completely replace the need for MV and support basal metabolic requirements.

Early use of an implantable diaphragm pacing stimulator for a child with severe acute flaccid myelitis-a case report.

Introduction: Acute Flaccid Myelitis (AFM) is a recently recognized, polio-like illness of children that can be functionally devastating. Severe cases can lead to ventilatory failure. Incomplete phrenic nerve injuries in other populations has been shown to respond to diaphragmatic stimulation. We therefore proposed an early assessment for incomplete denervation by laparoscopic direct stimulation of the diaphragm and placement of a diaphragmatic pacing system to enhance diaphragm function. Case presentation: A 3 year-old girl presented with AFM with clinically and electrodiagnostically severe involvement of all four limbs and muscles of respiration. Direct stimulation of the diaphragm demonstrated contraction and a diaphragmatic stimulator was placed at 3 weeks post presentation. The patient was immediately able to tolerate short bouts of reduced ventilation settings. Electromyography via the pacing wires demonstrated intact motor units consistent with partial denervation/reinnervation in the left hemidiaphragm, and no motor units in the right hemidiaphragm. At three months, she tolerated 6 h of pacing on pressure support setting. At 5 months she demonstrated larger tidal volumes with active pacing than without. Discussion: In our experience, AFM patients who require chronic ventilator support are rarely able to be weaned. Despite clinical and surface electrodiagnostic evidence of complete phrenic nerve involvement, the patient's diaphragm responded to direct stimulation. The patient preferred pacing over non-pacing times and showed improved ventilatory ability with pacing as opposed to without, though remains ventilator-dependent. These findings support augmentation of diaphragm function and possible enhanced recovery of spontaneous function.

Long-term experience with diaphragm pacing for traumatic spinal cord injury: Early implantation should be considered.

BACKGROUND: Cervical spinal cord injury can result in catastrophic respiratory failure requiring mechanical ventilation with high morbidity, mortality, and cost. Diaphragm pacing was developed to replace/decrease mechanical ventilation. We report the largest long-term results in traumatic cervical spinal cord injury. METHODS: In this retrospective review of prospective institutional review board protocols, all patients underwent laparoscopic diaphragm mapping and implantation of electrodes for diaphragm strengthening and ventilator weaning. RESULTS: From 2000 to 2017, 92 patients out of 486 diaphragm pacing implants met the criteria. The age at time of injury ranged from birth to 74 years (average: 27 years). Time on mechanical ventilation was an average of 47.5 months (range, 6 days to 25 years, median = 1.58 years). Eighty-eight percent of patients achieved the minimum of 4 hours of pacing. Fifty-six patients (60.8%) used diaphragm pacing 24 hours a day. Five patients had full recovery of breathing with subsequent diaphragm pacing removal. Median survival was 22.2 years (95% confidence interval: 14.0-not reached) with only 31 deaths. Subgroup analysis revealed that earlier diaphragm pacing implantation leads to greater 24-hour use of diaphragm pacing and no need for any mechanical ventilation. CONCLUSION: Diaphragm pacing can successfully decrease the need for mechanical ventilation in traumatic cervical spinal cord injury. Earlier implantation should be considered.

An Autopsy Case of Amyotrophic Lateral Sclerosis with Diaphragm Pacing.

Respiratory insufficiency is a critical problem in amyotrophic lateral sclerosis (ALS) patients. We herein present the case of an autopsied patient with sporadic ALS who underwent diaphragm pacing (DP). The pathology showed several localized adhesions with a markedly atrophied diaphragm. A marked loss of motor neurons with Bunina bodies and phosphorylated TDP-43 positive inclusions was found in the spinal cord and primary motor cortex. Mild hyalinization and a few multinucleated giant cells were present around the electrode tracks in the diaphragm. However, no infiltration of inflammatory cells was detected. Our findings suggest that full-time DP might not cause severe damage to adjacent diaphragm tissue.

Diaphragm Pacing as a Rehabilitative Tool for Patients With Pompe Disease Who Are Ventilator-Dependent: Case Series.

BACKGROUND AND PURPOSE: Pompe disease is an inherited disorder notable for severe, progressive ventilatory compromise. Although ventilatory failure has been attributed to myofiber dysfunction secondary to diaphragmatic glycogen accumulation, neural involvement of the phrenic motor system is also a prominent feature. Direct diaphragm pacing supplements respiratory function in other disorders of the phrenic motor system. Accordingly, it is hypothesized that augmented neuromuscular activity via diaphragm pacing would promote weaning from mechanical ventilation in patients with Pompe disease who are unresponsive to conventional, muscle-directed treatments. CASE DESCRIPTION: Three patients with Pompe disease developed diaphragm paresis that resulted in chronic mechanical ventilation dependence. After preoperative inspiratory muscle strengthening exercises failed to improve function, fine-wire pacing electrodes were laparoscopically implanted into the diaphragm. Diaphragm conditioning was initiated the first postoperative week and consisted of gradual increases in stimulation parameters, lengthening of stimulation sessions, and ventilator weaning. Ventilation and intramuscular electromyographic activity were recorded periodically during conditioning to quantify diaphragm neuromuscular function. OUTCOMES: During paced breathing without mechanical ventilation, tidal volumes increased, and 2 patients were weaned from daytime ventilator dependence within the first 3 months of pacing, which has been sustained over the long-term. A third patient reduced reliance on daytime ventilation, but weaning was delayed by malacia of the large airways. In all patients, pacing appeared to facilitate spontaneous phrenic motor unit activity during independent breathing without ventilator or pacer support. DISCUSSION: The findings are consistent with the view that diaphragm pacing has potential rehabilitative value to reduce reliance on mechanical ventilation in people with Pompe disease, but further study is needed. Diaphragm pacing represents a paradigm shift in the management of respiratory insufficiency for Pompe disease that warrants further controlled examination.

Identification of unexpected respiratory abnormalities in patients with amyotrophic lateral sclerosis through electromyographic analysis using intramuscular electrodes implanted for therapeutic diaphragmatic pacing.

BACKGROUND: Amyotrophic lateral sclerosis patients have significant respiratory abnormalities with incomplete understanding of respiratory control. This study analyzes electromyography (EMG) of the diaphragm (dEMG) using implanted diaphragm pacing (DP) electrodes. METHODS: Retrospective analysis of dEMG data were obtained during Institutional Review Board and US Food and Drug Administration approved trials. The electrodes were used to analyze epochs of dEMG during multiple respiratory cycles. RESULTS: Fifty-three patients were implanted. Thirty-six had bilateral dEMG assessments, 18 had continuous overnight readings with pulse oximetry, and 19 had serial analysis. Several findings revealed an alteration in the central respiratory drive including central apnea, hypoventilation, and hypercarbia. The electrodes showed unilateral dysfunction and demonstrated noninvasive ventilation suppression of diaphragm activity. DP can be used for serial monitoring, to decrease hypercarbia, improve sleep, and decrease atrophy. CONCLUSIONS: Multiple abnormalities of respiratory control can be seen in amyotrophic lateral sclerosis patients using dEMG through therapeutic DP electrodes. DP is used to overcome instability of respiratory control when there are intact diaphragm motor units leading to improved survival.

Extended use of diaphragm pacing in patients with unilateral or bilateral diaphragm dysfunction: a new therapeutic option.

BACKGROUND: Diaphragm dysfunction (DD) can cause sleep abnormalities, dyspnea, atelectasis, and respiratory failure. Historical treatments, including positive pressure ventilation or diaphragm plication, may alleviate symptoms but do not restore physiologic diaphragm function. Diaphragm pacing (DP) is approved for spinal cord-injured patients and in amyotrophic lateral sclerosis. We report a series of DD patients undergoing use of DP outside of these initial indications. METHODS: This report involves a prospective, nonrandomized, interventional trial under institutional review board approval at a single institution. DP involves laparoscopic motor point mapping with implantation of intramuscular electrodes in each hemidiaphragm. Postoperatively, diaphragm conditioning ensues. RESULTS: Twenty-seven patients were evaluated; all patients had symptomatic and objective hypoventilation for an average of 36 months of symptoms. Causes included idiopathic (n = 13), chest surgery (n = 5), shoulder surgery or trauma (n = 6), and others (n = 3); 17 had bilateral involvement, 6 had nonstimulable diaphragms and were not implanted, and 21 were implanted. Thirteen (62%) had substantial clinically relevant respiratory improvements. Four ventilator patients were weaned completely. Four had partial improvement, 3 had no improvement, and 1 patient was lost to follow-up for objective analysis. CONCLUSION: This is the first report of DP being used to treat diverse causes of DD. Eighty-one percent of implanted patients experienced improvements. This success suggests a potential for a wider use of DP and areas for future research.

Final analysis of the pilot trial of diaphragm pacing in amyotrophic lateral sclerosis with long-term follow-up: diaphragm pacing positively affects diaphragm respiration.

BACKGROUND: Respiratory insufficiency is the major cause of mortality in patients with amyotrophic lateral sclerosis or Lou Gehrig's disease. This is the final report of the diaphragm pacing (DP) pilot trial. METHODS: Patients underwent laparoscopic diaphragm electrode implantations and subsequent conditioning of diaphragms. Serial respiratory function tests were performed in the initial year and followed until death. RESULTS: Sixteen patients were implanted with no perioperative or unanticipated device-related adverse events. There were 452 implant-months of follow-up. DP allowed greater movement of the diaphragm under fluoroscopy, increased muscle thickness, and decreased the decline in forced vital capacity. Median survival from implant was 19.7 months with the cause of death respiratory in only 31%. CONCLUSIONS: Long-term analysis of DP in amyotrophic lateral sclerosis showed no safety issues and can positively influence diaphragm physiology and survival. This formed the initial basis for subsequent US Food and Drug Administration approval.

Electric ventilation: indications for and technical aspects of diaphragm pacing stimulation surgical implantation.

OBJECTIVE: Patients with high cervical spinal cord injury are usually dependent on mechanical ventilation support, which, albeit life saving, is associated with complications and decreased life expectancy because of respiratory infections. Diaphragm pacing stimulation (DPS), sometimes referred to as electric ventilation, induces inhalation by stimulating the inspiratory muscles. Our objective was to highlight the indications for and some aspects of the surgical technique employed in the laparoscopic insertion of the DPS electrodes, as well as to describe five cases of tetraplegic patients submitted to the technique. METHODS: Patient selection involved transcutaneous phrenic nerve studies in order to determine whether the phrenic nerves were preserved. The surgical approach was traditional laparoscopy, with four ports. The initial step was electrical mapping in order to locate the "motor points" (the points at which stimulation would cause maximal contraction of the diaphragm). If the diaphragm mapping was successful, four electrodes were implanted into the abdominal surface of the diaphragm, two on each side, to stimulate the branches of the phrenic nerve. RESULTS: Of the five patients, three could breathe using DPS alone for more than 24 h, one could do so for more than 6 h, and one could not do so at all. CONCLUSIONS: Although a longer follow-up period is needed in order to reach definitive conclusions, the initial results have been promising. At this writing, most of our patients have been able to remain ventilator-free for long periods of time.

Functional electrical stimulation: restoration of respiratory function.

Tetraplegia can lead to chronic respiratory failure. The need for tracheostomy mechanical ventilation significantly increases the cost of care, decreases the quality of life of the patient, and decreases life expectancy in spinal cord injury (SCI) because of pneumonias. Phrenic nerve stimulation was initially developed in the 1960s and diaphragm pacing was developed in the 1990s; both have the ability to remove a patient from positive pressure ventilation and allow them to breathe with their own diaphragm, decreasing posterior lung lobe atelectasis and pneumonia risk. This chapter summarizes the current surgical techniques, ventilator weaning options, and long-term results of functional electrical stimulation in restoring respiratory function.

Ventilação elétrica: indicações e aspectos técnicos do implante cirúrgico do marca-passo de estimulação diafragmática / Electric ventilation: indications for and technical aspects of diaphragm pacing stimulation surgical implantation

OBJETIVO: Pacientes com lesão medular cervical alta em geral são dependentes de ventilação mecânica, que, embora salve vidas, está associada a complicações e redução da expectativa de vida devido a infecções respiratórias. A estimulação do diafragma por marca-passo, às vezes chamada de ventilação elétrica, induz a inspiração por estimulação dos músculos inspiratórios. Nosso objetivo foi destacar as indicações e alguns aspectos da técnica cirúrgica empregada no implante laparoscópico dos eletrodos, assim como descrever cinco casos de pacientes tetraplégicos submetidos à técnica. MÉTODOS: A seleção dos pacientes envolveu estudos de condução do nervo frênico por via transcutânea para determinar se os nervos estavam preservados. A abordagem cirúrgica foi laparoscopia clássica, com quatro trocartes. A técnica foi iniciada com o mapeamento elétrico para encontrar os "pontos motores" (pontos de contração máxima do diafragma). Se o mapeamento era bem-sucedido, dois eletrodos eram implantados na face abdominal de cada lado do diafragma para estimular ramos do nervo frênico. RESULTADOS: Dos cinco pacientes, três e um, respectivamente, eram capazes de respirar somente com o uso do marca-passo por períodos superiores a 24 e 6 h, enquanto um não era capaz. CONCLUSÕES: Embora seja necessário um acompanhamento mais longo para chegar a conclusões definitivas, os resultados iniciais são promissores, pois, no momento, a maioria dos nossos pacientes pode permanecer sem ventilação mecânica por longos períodos de tempo.

OBJECTIVE: Patients with high cervical spinal cord injury are usually dependent on mechanical ventilation support, which, albeit life saving, is associated with complications and decreased life expectancy because of respiratory infections. Diaphragm pacing stimulation (DPS), sometimes referred to as electric ventilation, induces inhalation by stimulating the inspiratory muscles. Our objective was to highlight the indications for and some aspects of the surgical technique employed in the laparoscopic insertion of the DPS electrodes, as well as to describe five cases of tetraplegic patients submitted to the technique. METHODS: Patient selection involved transcutaneous phrenic nerve studies in order to determine whether the phrenic nerves were preserved. The surgical approach was traditional laparoscopy, with four ports. The initial step was electrical mapping in order to locate the "motor points" (the points at which stimulation would cause maximal contraction of the diaphragm). If the diaphragm mapping was successful, four electrodes were implanted into the abdominal surface of the diaphragm, two on each side, to stimulate the branches of the phrenic nerve. RESULTS: Of the five patients, three could breathe using DPS alone for more than 24 h, one could do so for more than 6 h, and one could not do so at all. CONCLUSIONS: Although a longer follow-up period is needed in order to reach definitive conclusions, the initial results have been promising. At this writing, most of our patients have been able to remain ventilator-free for long periods of time.

Multicenter analysis of diaphragm pacing in tetraplegics with cardiac pacemakers: positive implications for ventilator weaning in intensive care units.

BACKGROUND: Diaphragm pacing (DP) can replace mechanical ventilation in tetraplegics and in trials has assisted respiration in amyotrophic lateral sclerosis patients. This report describes results of DP in patients with cardiac pacemakers. METHODS: Prospective, single-center and multicenter, nonrandomized, controlled, interventional protocols under U.S. Food and Drug Administration and/or institutional review board approval were evaluated. Patients underwent laparoscopic diaphragm motor point mapping to identify optimal electrode site for implantation. With diaphragm conditioning, patients were weaned from their ventilator. Perioperative and long-term assessments between the cardiac pacemakers and DP were analyzed for any device-to-device interactions. RESULTS: Over 300 subjects were implanted from 2000 to 2010. Twenty tetraplegics with cardiac pacemakers and DP were analyzed from 6 sites. Subjects ranged from 19 to 61 years old with DP implantation 6 months to 24 years postinjury. There were no immediate or long-term device to device interactions. All patients achieved diaphragm-paced tidal volumes exceeding their basal requirements and, after conditioning, all patients could go >4 hours without mechanical ventilators; 71% could go 24 hours continuously. CONCLUSION: DP can be safely implanted in tetraplegics having cardiac pacemakers. Applications for temporary use of DP to maintain diaphragm type 1 muscle fiber and improve posterior lobe ventilation may benefit complex critical care patients.

Amyotrophic lateral sclerosis: the Midwestern surgical experience with the diaphragm pacing stimulation system shows that general anesthesia can be safely performed.

BACKGROUND: There is a paucity of literature concerning general anesthesia and surgery in patients with amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease). This report summarizes the largest series of surgical cases in ALS during multicenter prospective trials of the laparoscopic diaphragm pacing system (DPS) to delay respiratory failure. METHOD: The overall strategy outlined includes the use of rapidly reversible short-acting analgesic and amnestic agents with no neuromuscular relaxants. RESULTS: Fifty-one patients were implanted from March 2005 to March 2008 at 2 sites. Age at implantation ranged from 42 to 73 years and the percent predicted forced vital capacity (FVC) ranged from 20% to 87%. On preoperative blood gases, Pco(2) was as high as 60. Using this protocol, there were no failures to extubate or 30-day mortalities. The DPS system increases the respiratory system compliance by decreasing posterior lobe atelectasis and can stimulate respirations at the end of each case. CONCLUSIONS: Laparoscopic surgery with general anesthesia can be safely performed in patients with ALS undergoing DPS.

Complete worldwide operative experience in laparoscopic diaphragm pacing: results and differences in spinal cord injured patients and amyotrophic lateral sclerosis patients.

BACKGROUND: Diaphragm movement is essential for adequate ventilation, and when the diaphragm is adversely affected patients face lifelong positive-pressure mechanical ventilation or death. This report summarizes the complete worldwide multicenter experience with diaphragm pacing stimulation (DPS) to maintain and provide diaphragm function in ventilator-dependent spinal cord injury (SCI) patients and respiratory-compromised patients with amyotrophic lateral sclerosis (ALS). It will highlight the surgical experiences and the differences in diaphragm function in these two groups of patients. METHODS: In prospective Food and Drug Administration (FDA) trials, patients underwent laparoscopic diaphragm motor point mapping with intramuscular electrode implantation. Stimulation of the electrodes ensued to condition and strengthen the diaphragm. RESULTS: From March of 2000 to September of 2007, a total of 88 patients (50 SCI and 38 ALS) were implanted with DPS at five sites. Patient age ranged from 18 to 74 years. Time from SCI to implantation ranged from 3 months to 27 years. In 87 patients the diaphragm motor point was mapped with successful implantation of electrodes with the only failure the second SCI patient who had a false-positive phrenic nerve study. Patients with ALS had much weaker diaphragms identified surgically, requiring trains of stimulation during mapping to identify the motor point at times. There was no perioperative mortality even in ALS patients with forced vital capacity (FVC) below 50% predicted. There was no cardiac involvement from diaphragm pacing even when analyzed in ten patients who had pre-existing cardiac pacemakers. No infections occurred even with simultaneous gastrostomy tube placements for ALS patients. In the SCI patients 96% were able to use DPS to provide ventilation replacing their mechanical ventilators and in the ALS studies patients have been able to delay the need for mechanical ventilation up to 24 months. CONCLUSION: This multicenter experience has shown that laparoscopic diaphragm motor point mapping, electrode implantation, and pacing can be safely performed both in SCI and in ALS. In SCI patients it allows freedom from ventilator and in ALS patients it delays the need for ventilators, increasing survival.

Diaphragm pacing stimulation system for tetraplegia in individuals injured during childhood or adolescence.

BACKGROUND: Children with cervical spinal cord injury and chronic respiratory insufficiency face the risks and stigma associated with mechanical ventilators. The Diaphragm Pacing Stimulation (DPS) System for electrical activation of the diaphragm is a minimally invasive alternative to mechanical ventilation. METHODS: Review of patients in a prospective Food and Drug Administration trial of the DPS System in individuals who were injured at age 18 years or younger. The procedure involved laparoscopic mapping to locate the diaphragm motor points with electrode implantation. Two weeks after surgery, stimulus/output characteristics of each electrode were determined to obtain an adequate tidal volume for ventilation. A home-based weaning protocol from the ventilator was used. RESULTS: Of 28 patients implanted with the DPS System, 10 had sustained cervical SCI as children or adolescents. Average age at injury was 13 years (range 1.5 to 17 y). Age at implantation ranged from 18 to 34 years. Length of time from injury to implantation averaged 9.7 years (0.8 to 19 y). All patients tolerated the implantation procedure. Four patients utilize DPS continuously (24/7), 4 patients pace daytime only, and 2 patients are still actively conditioning their diaphragms. Two patients required surgical correction of scoliosis prior to implantation. All patients prefer breathing with the DPS and would recommend it to others; 4 patients specifically identified that attending college or church without a ventilator eases their integration into society. CONCLUSIONS: The results show that the laparoscopic DPS system can be safely implanted in tetraplegics injured as children and used in a home-based environment to wean them off of mechanical ventilation.

Inspiratory muscle pacing in spinal cord injury: case report and clinical commentary.

BACKGROUND/OBJECTIVE: A significant fraction of patients with cervical spinal cord injury suffer from respiratory muscle paralysis and dependence on chronic mechanical ventilation. In selected patients, diaphragm pacing (DP) through electrical stimulation of the phrenic nerves provides an alternative to mechanical ventilation with significant advantages in life quality. METHODS: A case report of an individual who successfully underwent DP using intramuscular diaphragm electrodes. A brief review of the state of the art of DP including the clinical benefits of DP, patient selection and evaluation, description of equipment, methods of transition from mechanical ventilation to DP, potential complications and side effects, long-term outcome, and potential future developments in this field is included. RESULTS: Several available DP systems are available, including conventional ones in which electrodes are positioned directly on the phrenic nerves through thoracotomy and less invasive systems in which electrodes are placed within the diaphragm through laparoscopy. For patients with only unilateral phrenic nerve function, a combined intercostal and unilateral diaphragm pacing system is under development. CONCLUSIONS: In patients with ventilator-dependent tetraplegia, there are alternative methods of ventilatory support, which offer substantial benefits compared to mechanical ventilation.

Phrenic nerve pacing via intramuscular diaphragm electrodes in tetraplegic subjects.

CONTEXT: Diaphragm pacing in ventilator-dependent tetraplegic subjects is usually achieved by the placement of phrenic nerve electrodes via thoracotomy. However, this technique may be accomplished less invasively via laparoscopic placement of IM electrodes, at a lower cost and with less risk of injury to the phrenic nerve. OBJECTIVE: To assess the feasibility of laparascopic placement of IM diaphragm electrodes to achieve long-term ventilatory support in ventilator-dependent tetraplegic subjects. DESIGN, SETTING, AND PARTICIPANTS: Two IM diaphragm electrodes were placed laparoscopically in each hemidiaphragm in five subjects with ventilator-dependent tetraplegia. Studies were performed either on an outpatient basis or with a single overnight hospitalization. Ventilator-dependent tetraplegic subjects were identified in whom bilateral phrenic nerve function was present, as determined by phrenic nerve conduction studies. Following electrode placement, subjects participated in a conditioning program to improve the strength and endurance of the diaphragm over a period of 15 to 25 weeks. The duration of the study was variable depending on the time necessary to determine the maximum duration that individuals could be maintained without mechanical ventilation support. MAIN OUTCOME MEASURES: Magnitude of inspired volume generation and duration of ventilatory support with bilateral diaphragm pacing alone. RESULTS: In four of the five subjects studied, initial bilateral diaphragm stimulation resulted in inspired volumes between 430 and 1,060 mL. Reconditioning of the diaphragm over several weeks resulted in substantial increases in inspired volumes to 1,100 to 1,240 mL. These subjects were comfortably maintained without mechanical ventilatory support for prolonged time periods by diaphragm pacing, by full-time ventilatory support in three subjects, and 20 h per day, in the fourth subject. No response to stimulation was observed in one subject, most likely secondary to denervation atrophy. CONCLUSIONS: Diaphragm pacing in ventilator-dependent tetraplegic subjects can be successfully achieved via laparascopic placement of IM electrodes.

Mapping the phrenic nerve motor point: the key to a successful laparoscopic diaphragm pacing system in the first human series.

BACKGROUND: For patients with high spinal cord injury and chronic respiratory insufficiency, electrically induced diaphragm pacing is an alternative to long-term positive pressure ventilation. The goal of this study was to laparoscopically assess the phrenic nerve motor point of the diaphragm and then implant electrodes to produce chronic negative pressure ventilation. METHODS: Patients undergoing elective laparoscopic procedures (volunteer patient group) underwent a series of electrical stimuli (2 to 24 mA at 100-microsecond pulse widths) with a mapping probe to identify the motor point through qualitative visualization of diaphragm motion and quantitative measurement of the abdominal pressure to assess the strength of the contraction. After Food and Drug Administration and Institutional Review Board approval, tetraplegic patients (spinal cord injured patient group) who were ventilator dependent underwent mapping and implantation of electrodes for pacing in both diaphragms. RESULTS: In the volunteer group, 28 patients underwent 3 to 50 stimulations per diaphragm to identify the motor points. Throughout this series the surgical tools and software were improved to allow rapid motor point location with a grid-mapping algorithm. In the spinal cord injured group, 5 of 6 patients had electrodes successfully implanted at the motor point to produce adequate tidal volumes. The one failure caused a change in our inclusion criteria to include fluoroscopic confirmation of diaphragm movement during surface nerve stimulation. Three patients are completely free of the ventilator, and the other 2 are progressively increasing their time off the ventilator with conditioning. CONCLUSIONS: Mapping and implantation of the electrodes can be done laparoscopically, providing for a low-risk, cost-effective, outpatient, diaphragm pacing system that will support the respiratory needs of patients.

Phrenic nerve pacing in a tetraplegic patient via intramuscular diaphragm electrodes.

In patients with ventilator-dependent tetraplegia, phrenic nerve pacing (PNP) provides significant clinical advantages compared with mechanical ventilation. This technique however generally requires a thoracotomy with its associated risks and in-patient hospital stay and carries some risk of phrenic nerve injury. We have developed a method by which the phrenic nerves can be activated via intramuscular diaphragm electrodes. In one patient with ventilator-dependent tetraplegia, two intramuscular diaphragm electrodes were implanted into each hemidiaphragm near the phrenic nerve motor points via laparoscopic surgery. The motor points were identified employing a previously devised mapping technique. Because inspired volumes were suboptimal on the right, a second laparoscopic procedure was necessary to position electrodes near the anterior and posterior branches of the right phrenic nerve. During bilateral stimulation, inspired volume was 580 ml. After a reconditioning program of progressively increasing diaphragm pacing, maximum inspired volumes on the left and right hemidiaphragms increased significantly. Maximum combined bilateral stimulation was 1120 ml. Importantly, the patient has been able to comfortably tolerate full-time pacing. If confirmed in additional patients, PNP with intramuscular diaphragm electrodes via laparoscopic surgery may provide a less invasive and less costly alternative to conventional PNP.