How to cite this article: Bose R, Banerjee AD, Brajesh V, Narang KS, Dubey S, Singh VP. Phrenic nerve stimulation for diaphragmatic pacing in chronic ventilator-dependent patients. Neurol India 2018;66:1834-7
How to cite this URL: Bose R, Banerjee AD, Brajesh V, Narang KS, Dubey S, Singh VP. Phrenic nerve stimulation for diaphragmatic pacing in chronic ventilator-dependent patients. Neurol India [serial online] 2018 [cited 2022 May 28];66:1834-7. Available from: https://www.neurologyindia.com/text.asp?2018/66/6/1834/246256
Patients of brain stem or high cervical cord pathologies often become terminally ventilator-dependent. This poses a mammoth medical and socio-economic burden on the family. Mechanical ventilation is not physiological, may cause infection, limits ambulation, and is emotionally taxing, especially on young patients. To address these issues, Judson and Glenn first reported the use of an electrical diaphragmatic stimulation. Initially, electric pulse generators, specifically tailored for such purpose, were being used. As a subsequent improvization, Taira et al., reported the use of electrical stimulators, used in spinal cord stimulation and deep brain stimulation, for phrenic nerve stimulation. We present here our experience of one such case where phrenic nerve stimulators have been implanted.
Our patient was a 30-year old male patient who had suffered from a traumatic C5 body fracture with a high cervical cord contusion. He had undergone C5 corpectomy with decompression and fusion at another hospital. He had been quadriplegic, bowel/bladder incontinent, and ventilator dependent for >3 months. The patient was planned for phrenic nerve stimulator placement. Bedside trial of percutaneous stimulation (using standard parameters) of bilateral cervical phrenic nerves was performed successfully. Subsequently, after a prior informed consent, he was taken up for bilateral phrenic nerve stimulation system implantation surgery. General anesthesia was induced and the patient was kept in the supine position with mild neck extension. On either side, the phrenic nerve was exposed through the posterior triangle of neck [Figure 1]. Clinical and fluoroscopic recording [Figure 2] and [Video 1], [Video 2] was made of robust diaphragmatic contractions with cyclic monopolar stimulation of up to 2 mAmp, 50 Hz, 100 μs pulse width parameters with the NIM-Eclipse Nerve Stimulator System (Medtronic, MN, USA). Then, the quadripolar cylindrical stimulator leads (Brio Rechargeable Deep Brain Stimulation [DBS] System with 4-contact brain electrodes, Abbott International, Plano, TX, USA) were tethered to respective phrenic nerves by taking silk suture with the perineural soft tissue [Figure 3]. The lead wires from both sides were tunneled [Figure 4] subcutaneously to the anterior chest wall over the left infraclavicular area, where a subcutaneous pocket [Figure 5] was created for the intermittent pulse generator (Brio Rechargeable IPG, Abbott International, Plano, TX, USA). The wires were connected to the pulse generator, which was then placed and anchored in the subcutaneous pocket [Figure 6]. After irrigation with an antibiotic solution, the incisions were closed.
Figure 1: Landmarks for isolation of phrenic nerve
The stimulation was started the next day [Figure 7]. The end-tidal carbon dioxide pressure was adjusted to about 400 mm Hg by changing the output strength of the implantable pulse generator (IPG) with continuous monitoring of the same and oxygen saturation levels. The IPG parameters of chronic stimulation were cyclic bipolar mode (2 s on, 3 s off; left side 1 − 2+; right side 10 − 11+; amplitude 1.5 V; rate 22 Hz; pulse width 175 μs) with alternate phrenic nerve stimulations every 12 h to avoid diaphragmatic fatigue.
Figure 7: Programming of the implanted neurostimulator
The patient was gradually weaned off from the ventilator within 3 weeks. Thereafter, he only needs intermittent bilevel positive airway pressure (BiPAP) support. Seven months after the onset of diaphragm pacing, he is now ambulatory in a wheelchair with ongoing neurorehabilitation.
In 1786, Caldani first noted diaphragmatic movement when the phrenic nerve was electrically stimulated. In 1873, Hefeland suggested the phrenic nerve stimulation to treat neonatal asphyxia. However with the emergence of mechanical ventilators, phrenic nerve stimulation took a back-stage. Almost after a 100 years, Glenn and Phelps demonstrated the feasibility of long-term continuous pacing of the conditioned diaphragm in selected cases.
Diaphragmatic pacing is done with a low frequency cyclical electrical stimulation. This conditions the diaphragmatic muscles rendering them fatigue-free. The conditioning of the diaphragm is a process whereby the fast-contracting, anaerobic, highly glycolytic fibers (fatigue prone) are converted to slow-contracting, aerobic oxidative fibers (fatigue-resistant). This helps to maintain the physiological breathing process by stimulation of the phrenic nerve, independent of the mechanical ventilator., A prolonged follow up duration with clinical observation and spirometry has showed the absence of fatigue after a similar pacing of the diaphragm.
Patients having pathology of the respiratory center of the brain stem or disruption of the upper motor neuron pathways (above spinal C3 level) of the phrenic nerve, benefit from diaphragm pacing. The phrenic nerve and the diaphragm need to remain physiologically intact. This is checked pre-operatively by transcutaneous stimulation of the phrenic nerve at the neck level.
Like in many other countries,, we used a deep brain stimulator instead of the commercially available thoracic phrenic nerve stimulation system (Avery Laboratories Inc.) as the latter is not available in our country. Taira and Hori have successfully demonstrated the efficacy of phrenic nerve stimulation in four patients with central apnea due to brain stem injuries, using deep brain or spinal cord stimulators.
The electrodes for diaphragmatic pacing can be implanted at the thoracic or cervical levels [Table 1].,,,,,,, Some surgeons prefer the thoracic approach as the course of the phrenic nerve in the anterior scalene space is variable, and the accessory phrenic nerve joins the main trunk only at the mediastinal level; however, we have chosen the cervical approach due to its technical simplicity, lower morbidity, and also to allow bilateral electrode placement at one go.
Table 1: Different methods of diaphragmatic pacing
For chronic ventilator-dependent patients with central hypoventilation, diaphragmatic pacing by phrenic nerve stimulation is a viable last resort to wean them off ventilator, thereby facilitating ambulation, physiotherapy, and psychosocial improvement.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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