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Diaphragmatic Pacing


Diaphragmatic Pacing

Article Author:
Rishik Vashisht
Article Editor:
Yuvraj Chowdhury
Updated:
11/29/2020 7:32:16 PM
For CME on this topic:
Diaphragmatic Pacing CME
PubMed Link:
Diaphragmatic Pacing

Introduction

Diaphragm dysfunction an underdiagnosed condition and causes unexplained dyspnea. The dysfunction can range from partial weakness to complete paralysis of either one hemidiaphragm or both hemidiaphragm.[1] Spinal cord injuries (SCI) and critical care polyneuropathies encompass a big chunk of the cases of diaphragmatic dysfunction. According to the National Spinal Cord Injury Statistics Center, the incidence of traumatic SCI in the United States was approximately 17,000 in 2016.[2] 

Diaphragmatic paralysis usually results from a high spinal cord injury, whereas mid-cervical lesions lead to partial weakness. SCI leads to chronic impairment and disability. Half of these patients develop tetraplegia, with 4% of these patients requiring long term mechanical ventilation.[3] Critical illness polyneuropathy (CIP) is a common complication of critical illness affecting the motor and sensory neurons.[4] Muscle involvement causing loss of muscle mass and eventual weakness has been referred to as critical illness myopathy. The involvement of the phrenic nerve and diaphragm leads to its weakness and, at times, complete paralysis. These patients have worse outcomes with prolonged weaning, higher hospital length of stays, and dependency on mechanical ventilation.[5] 

Traditional approaches to management have been mainly focused on waiting for recovery through innervation while supporting the patient on mechanical ventilation. However, this is fraught with complications. In the past few years, diaphragm pacing (DP) has been a proven therapy to wean SCI patients from mechanical ventilation (MV).[6] A small feasibility study evaluating DP in critically ill mechanically ventilated patients demonstrated that the diaphragm could significantly help with the work of breathing when activated by a catheter-based, transvenous DP.[7] A large multi-center randomized clinical trial (RESCUE 2) is underway to compare temporary transvenous diaphragm pacing vs. standard of care for weaning from mechanical ventilation.[8]

Anatomy and Physiology

The diaphragm is a dome-shaped structure that separates the abdominal and thoracic cavity. It's composed of slow-twitch type I and fast-twitch type IIa myofibers. These muscle fibers originate from the lumbar vertebrae and abdominal wall, the ribs, and the xiphoid process and floating ribs. Its innervated by phrenic nerves that arise from the nerve roots from C3 to C5. The phrenic nerve trifurcates at the dome of the diaphragm just prior to enervation. Diaphragm opposes the lower rib cages from the sides called a zone of apposition. As the diaphragm contracts, it pushes down into the abdominal cavity, generating a negative pressure in the lungs, which drives the air into the lungs. As the diaphragm relaxes, the elastic recoil of the lungs pushes the air out. In a cervical SCI, there is direct damage to the respiratory bulbospinal pathways. In higher SCI, the spinal roots to phrenic nerves are spared; however, there is an interruption in the roots from the respiratory center in the brain to the medulla.[3]

Indications

Patients with SCI above C3 are the most obvious candidates as their phrenic nerve is intact and can be easily stimulated. Their phrenic nerve can be stimulated at either neck, thorax, or diaphragm. In comparison, patients with mid-cervical SCI cannot be stimulated at neck or thorax levels as their phrenic nerve is not functional. An advanced technique of stimulating the nerve endings at the insertion of the diaphragm has shown promising results (direct diaphragmatic pacing stimulation).

Other indications include disorders like congenital central alveolar hypoventilation, Arnold-Chiari malformations, basilar meningitis, brainstem tumors, strokes, Pompe disease, syringomyelia, and meningomyelocele.[9] There have been published case series and reports of DP being successfully used in patients with accidental unilateral phrenic nerve injuries and lower motor neuron diseases like Charcot Marie Tooth disease, spinal muscular atrophy, polio, diaphragmatic flutter, and acute flaccid myelitis.[6][10]

Contraindications

Controversy surrounds the use of DP in patients with amyotrophic lateral sclerosis (ALS). One study showed improved survival by delaying the need for mechanical ventilation.[11] The authors of this trial did a long term follow up of these patients and confirmed their original findings.[12] However, there are two trials that have shown decreased survival in these patients.[13][14] Until more conclusive evidence is available showing clear benefit, we suggest weighing the risks and benefits of the procedure with a team in a specialized center. DP should not be done in patients who do have phrenic nerve function as determined by nerve conduction studies.

Equipment

There are two common varieties of diaphragmatic pacers:

  • Conventional DP - An internal electrode is attached to the phrenic nerve at cervical, thoracic, or diaphragmatic level. Pacing wires connect this electrode to a receiver under the skin. An external transmitting box is placed above the receiver on the surface of the skin. This box is the main control unit and emits radiofrequency signals.
  • Diaphragmatic Pacing System (DPS) - DPS consists of four electrodes implanted in the diaphragm to provide direct muscle stimulation and a fifth electrode implanted under the skin, which acts as a grounder. An electrode connector groups the five electrodes exiting the skin into a socket called an external pulse generator (EPG). A removable cable connects the electrode socket to the EPG.

Personnel

Diaphragm pacing requires an interprofessional team approach before and after the surgery. Alongside the surgeon who performs the procedure, neurology consultation should be sought for careful performance and interpretation of the phrenic nerve conduction velocities prior to surgery. These patients are usually severely deconditioned at the time of surgery and need a skilled rehabilitation team consisting of physical medicine and rehabilitation physician, physical therapist, occupational therapist, and speech therapist.

Preparation

Patient selection is the key step in preparation, as discussed above. Phrenic nerve conduction velocities should be done to assess the viability of the phrenic nerve. Preoperative workup should be done in accordance with the institute’s protocol. These patients should have a tracheostomy prior to the surgery. DP can cause sudden upper airway closure due to dyssynchronous muscle contractions of the diaphragm and upper airway. Tracheostomy acts as emergency access to the airway in case of such an event. A careful anesthesia plan needs to be in place prior to surgery. The use of paralytic agents must be avoided intraoperatively, as the phrenic nerve is stimulated to assess for diaphragmatic muscle contraction.[15]

Technique

There are three approaches to placing the pacing electrodes depending upon the position of placement, i.e., cervical, thoracic, and diaphragmatic.

  • Cervical approach - The nerve is identified in the mid-portion of the neck under the scalene fat pad by retraction of sternocleidomastoid (SCM) muscle.[16] The nerve is tested again by a stimulator and identifying the muscle contraction by fluoroscopy. Once tested, the fascial coverings are carefully dissected off. Two electrodes are hooked onto the nerve and secured to underlying connective tissue. A wire is tunneled subcutaneously that connects the electrodes to a pulse generator, which is also placed subcutaneously on the ipsilateral side of the chest.
  • The thoracic approach is usually undertaken via video-assisted thoracoscopic surgery (VATS).[17] The right phrenic nerve is found just posterior to the esophagus, and the left phrenic nerve is located lateral to the pericardium. Once the nerve is identified, it is freed from its fibrous sheath, and electrodes are hooked onto the nerve. The nerve is tested in a similar fashion as in the cervical approach. Pacemakers are usually placed one at a time two weeks apart.
  • Pacing through the diaphragmatic approach is done laparoscopically.[17] The electrodes are attached to the insertion points of the phrenic nerve to the diaphragm. These points are mapped out intraoperatively by phrenic nerve stimulation. Once all the electrodes are connected, the connecting wire is brought out through the epigastric port and connected to the EPG (placed in a subcutaneous pocket in the chest).

Complications

Potential complications include but are not limited to intraoperative damage to the phrenic nerve, vascular injuries, acute lung injury, pericardial and esophageal injuries, diaphragmatic perforation, viscous perforation, and peritonitis.

Clinical Significance

Diaphragm pacing is a therapy aimed at patients with ventilatory failure due to bilateral diaphragm paresis or paralysis. This is aimed at giving these patients an opportunity to become free or delay the need for invasive mechanical ventilation, improving the quality of life. DP is a relatively rare procedure, so patients should be evaluated at centers of expertise.  

Enhancing Healthcare Team Outcomes

Diaphragm pacing is a perfect example of the need for an interprofessional team for improving outcomes in patients. This procedure not only involves physicians across specialties, but there is also consistent involvement of ancillary services like nursing care, physical therapy, occupational therapy, and speech therapy. The rehabilitative process involves diaphragmatic conditioning after pacer implantation, which can take a long time. Education of all ancillary staff to identify clinical signs and symptoms of pacemaker malfunction and timely communication to the treating physician is the key to the successful rehabilitation of these patients. [Level 4]


References

[1] McCool FD,Tzelepis GE, Dysfunction of the diaphragm. The New England journal of medicine. 2012 Mar 8;     [PubMed PMID: 22397655]
[2] Eckert MJ,Martin MJ, Trauma: Spinal Cord Injury. The Surgical clinics of North America. 2017 Oct;     [PubMed PMID: 28958356]
[3] Dalal K,DiMarco AF, Diaphragmatic pacing in spinal cord injury. Physical medicine and rehabilitation clinics of North America. 2014 Aug;     [PubMed PMID: 25064791]
[4] Bolton CF,Laverty DA,Brown JD,Witt NJ,Hahn AF,Sibbald WJ, Critically ill polyneuropathy: electrophysiological studies and differentiation from Guillain-Barré syndrome. Journal of neurology, neurosurgery, and psychiatry. 1986 May;     [PubMed PMID: 3011996]
[5] Hermans G,De Jonghe B,Bruyninckx F,Van den Berghe G, Clinical review: Critical illness polyneuropathy and myopathy. Critical care (London, England). 2008;     [PubMed PMID: 19040777]
[6] Onders RP,Elmo M,Kaplan C,Katirji B,Schilz R, Extended use of diaphragm pacing in patients with unilateral or bilateral diaphragm dysfunction: a new therapeutic option. Surgery. 2014 Oct;     [PubMed PMID: 25239317]
[7] Reynolds S,Ebner A,Meffen T,Thakkar V,Gani M,Taylor K,Clark L,Sadarangani G,Meyyappan R,Sandoval R,Rohrs E,Hoffer JA, Diaphragm Activation in Ventilated Patients Using a Novel Transvenous Phrenic Nerve Pacing Catheter. Critical care medicine. 2017 Jul;     [PubMed PMID: 28441238]
[8] Evans D,Shure D,Clark L,Criner GJ,Dres M,de Abreu MG,Laghi F,McDonagh D,Petrof B,Nelson T,Similowski T, Temporary transvenous diaphragm pacing vs. standard of care for weaning from mechanical ventilation: study protocol for a randomized trial. Trials. 2019 Jan 17;     [PubMed PMID: 30654837]
[9] DiMarco AF, Diaphragm Pacing. Clinics in chest medicine. 2018 Jun;     [PubMed PMID: 29779603]
[10] Edmiston TL,Elrick MJ,Kovler ML,Jelin EB,Onders RP,Sadowsky CL, Early use of an implantable diaphragm pacing stimulator for a child with severe acute flaccid myelitis-a case report. Spinal cord series and cases. 2019;     [PubMed PMID: 31632725]
[11] Onders RP,Elmo M,Khansarinia S,Bowman B,Yee J,Road J,Bass B,Dunkin B,Ingvarsson PE,Oddsdóttir M, Complete worldwide operative experience in laparoscopic diaphragm pacing: results and differences in spinal cord injured patients and amyotrophic lateral sclerosis patients. Surgical endoscopy. 2009 Jul;     [PubMed PMID: 19067067]
[12] Onders RP,Elmo M,Kaplan C,Katirji B,Schilz R, Final analysis of the pilot trial of diaphragm pacing in amyotrophic lateral sclerosis with long-term follow-up: diaphragm pacing positively affects diaphragm respiration. American journal of surgery. 2014 Mar;     [PubMed PMID: 24439161]
[13] Safety and efficacy of diaphragm pacing in patients with respiratory insufficiency due to amyotrophic lateral sclerosis (DiPALS): a multicentre, open-label, randomised controlled trial. The Lancet. Neurology. 2015 Sep;     [PubMed PMID: 26234554]
[14] Gonzalez-Bermejo J,Morélot-Panzini C,Tanguy ML,Meininger V,Pradat PF,Lenglet T,Bruneteau G,Forestier NL,Couratier P,Guy N,Desnuelle C,Prigent H,Perrin C,Attali V,Fargeot C,Nierat MC,Royer C,Ménégaux F,Salachas F,Similowski T, Early diaphragm pacing in patients with amyotrophic lateral sclerosis (RespiStimALS): a randomised controlled triple-blind trial. The Lancet. Neurology. 2016 Nov;     [PubMed PMID: 27751553]
[15] Tedde ML,Vasconcelos Filho P,Hajjar LA,de Almeida JP,Flora GF,Okumura EM,Osawa EA,Fukushima JT,Teixeira MJ,Galas FR,Jatene FB,Auler JO Jr, Diaphragmatic pacing stimulation in spinal cord injury: anesthetic and perioperative management. Clinics (Sao Paulo, Brazil). 2012 Nov;     [PubMed PMID: 23184201]
[16] Glenn WW,Holcomb WG,Gee JB,Rath R, Central hypoventilation; long-term ventilatory assistance by radiofrequency electrophrenic respiration. Annals of surgery. 1970 Oct;     [PubMed PMID: 5458627]
[17] Le Pimpec-Barthes F,Legras A,Arame A,Pricopi C,Boucherie JC,Badia A,Panzini CM, Diaphragm pacing: the state of the art. Journal of thoracic disease. 2016 Apr;     [PubMed PMID: 27195135]