MaryJo Elmo

Diaphragm pacing with natural orifice transluminal endoscopic surgery: potential for difficult-to-wean intensive care unit patients.

BackgroundUp to 50% of the patients in the intensive care unit (ICU) require mechanical ventilation, with 20% requiring the use of a ventilator for more than 7 days. More than 40% of this time is spent weaning the patient from mechanical ventilation. Failure to wean from mechanical ventilation can in part be attributable to rapid onset of diaphragm atrophy, barotrauma, posterior lobe atelectasis, and impaired hemodynamics, which are normally improved by maintaining a more natural negative chest pressure. The authors have previously shown that laparoscopic implantation of a diaphragm pacing system benefits selected patients. They now propose that an acute ventilator assist with interventional neurostimulation of the diaphragm in the ICU is feasible and could facilitate the weaning of ICU patients from mechanical ventilation. Natural orifice transluminal endoscopic surgery (NOTES) has the potential to expand the benefits of the diaphragm pacing system to this acute patient population by allowing it to be performed at the bedside similarly to insertion of the common gastrostomy tube. This study evaluates the feasibility of this approach in a porcine model.MethodsPigs were anesthetized, and peritoneal access with the flexible endoscope was obtained using a guidewire, needle knife cautery, and balloon dilation. The diaphragm was mapped using a novel endoscopic electrostimulation catheter to locate the motor point (where stimulation provides complete contraction of the diaphragm). An intramuscular electrode then was placed at the motor point with a percutaneous needle. The gastrotomy was managed with a gastrostomy tube.ResultsFour pigs were studied, and the endoscopic mapping instrument was able to map the diaphragm to identify the motor point. In one animal, a percutaneous electrode was placed into the motor point under transgastric endoscopic visualization, and the diaphragm could be paced in conjunction with mechanical ventilation.ConclusionsThese animal studies demonstrate the feasibility of transgastric mapping of the diaphragm and implantation of a percutaneous electrode for therapeutic diaphragmatic stimulation.

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 Gehrigs 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.

Phrenic nerve conduction studies in spinal cord injury: Applications for diaphragmatic pacing

The diaphragm pacing system (DPS) is a minimally invasive alternative to mechanical ventilation in patients with quadriplegia due to cervical myelopathy primarily caused by high cervical spinal cord injury. We evaluated 36 patients, 29 of whom had traumatic spinal cord injury, two who had a history of remote meningitis and demyelinating disease, and five who had cervical myelopathies of unknown etiology. Phrenic nerve conduction studies were performed with simultaneous fluoroscopic observation of diaphragm excursion to assess diaphragm viability. In the preoperative evaluation, diaphragm compound muscle action potentials (CMAPs) were recorded only when the diaphragm moved on fluoroscopy with ipsilateral stimulation. Twenty‐six patients who were determined to have a viable diaphragm underwent DPS. Following DPS the primary outcome was the time (hours per day) that patients were able to pace and stay off the ventilator. Of 26 implanted patients, 96% (25 patients) were able to pace and tolerate being off the ventilator for more than 4 h per day. This study demonstrates that the presence of a diaphragm CMAP is associated with diaphragm movement observed by fluoroscopy in cervical myelopathy. In addition, DPS can help patients with cervical spinal cord injury to breathe unassisted by a ventilator. Muscle Nerve 38: 1546–1552, 2008

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 Gehrigs 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.

First reported experience with intramuscular diaphragm pacing in replacing positive pressure mechanical ventilators in children

PURPOSE Diaphragm pacing (DP) has been shown to successfully replace mechanical ventilators for adult tetraplegic patients with chronic respiratory insufficiency. This is the first report of DP in ventilator-dependent children. METHODS This was a prospective interventional experience under institutional review board approval. Diaphragm pacing involves outpatient laparoscopic diaphragm motor point mapping to identify the site where stimulation causes maximum diaphragm contraction with implantation of 4 percutaneous intramuscular electrodes. Diaphragm conditioning ensues to wean the child from the ventilator. RESULTS Six children were successfully implanted ranging from 5 to 17 years old with the smallest 15 kg in weight. Length of time on mechanical ventilation ranged from 11 days to 7.6 years with an average of 3.2 years. In all patients, DP provided tidal volumes above basal needs. Five of the patients underwent a home-based weaning program, whereas one patient who was implanted only 11 days post spinal cord injury never returned to the ventilator with DP use. Another patient was weaned from the ventilator full time but died of complications of his underlying brain stem tumor. The remaining patients weaned from the ventilator for over 14 hours a day and/or are actively conditioning their diaphragms. CONCLUSION Diaphragm pacing successfully replaced mechanical ventilators, which improves quality of life.

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.

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.