Diaphragm Pacing

Updated: Aug 14, 2017
  • Author: Shabir Bhimji, MD, PhD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Overview

Background

The history of pacing the diaphragm is not new. The earliest record of phrenic stimulation for the treatment of asphyxia was reported in 1783. In the mid-1850s, French neurologists also proposed such an idea, but it was Hugo Wilhelm von Ziemssen who performed the first diaphragmatic pacing on a young female patient who had asphyxiated on charcoal vapor. Several decades later, Duchenne also commended the benefits of diaphragmatic stimulation. Diaphragmatic stimulation did not gain any momentum because of the crude nature of surgery and lack of appropriate anesthesia. The technique was revived about a century later by Sarnoff and colleagues at Harvard, where they paced the phrenic nerve in dogs. Later, they applied the technique to a young child with complete respiratory paralysis following an intracranial aneurysm rupture. However, the true beginnings of diaphragmatic pacing started in the 1860s and 70s. The father of modern diaphragm pacing is Dr William W L Glenn from Yale University, who showed that the technique was not only practical but could be used clinically for the treatment for several medical disorders.

By the mid-1890s, there were isolated case reports that phrenic nerve stimulation was a viable option in patients who required permanent ventilatory support for a variety of reasons. With advances in technology, more refined and flexible electrodes were developed, and the thorascopic method of implantation became practical.

In the past, diaphragmatic pacing was always done by stimulating the phrenic nerve, but this changed when Synapse Biomedical developed a method to implant electrodes directly on the diaphragmatic muscle. The company developed the NeuRx device, which has received FDA approval for Humanitarian Device Exemption for use in patients with ALS and spinal cord injury.

Today, there are 3 commercially available devices that can stimulate the diaphragm—namely, the Synapse Biomedical NeuRx; the Mark IV Breathing Pacemaker, made by Avery Biomedical Devices; and the Atrotech OY's Atrostim PNS. The Avery and the Synapse devices are available in the United States and approved by the FDA. The Atrotech device is only available in Europe.

Currently, several renowned clinical centers offer diaphragm pacing for selected patients. [1, 2, 3, 4, 5, 6]

It should be noted that diaphragmatic pacing systems are still cumbersome (ie, the implantable pacemakers and AICDs), though work is currently being done on more portable miniature systems. All currently available systems involve an external transmitter and an implanted receiver, but fully implantable diaphragmatic pacing systems are being developed. The improved pacing systems now being used are more affordable and much easier to implant than the earlier systems. [7, 8]

See the images below.

The newest approach to diaphragmatic pacing; the p The newest approach to diaphragmatic pacing; the pacing electrodes are introduced via laparoscopy from the left chest.
The older method of phrenic nerve stimulation for The older method of phrenic nerve stimulation for diaphragmatic pacing.
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Indications and Contraindications

Diaphragm pacing is performed to provide ventilatory support in 2 main clinical scenarios, as follows:

  • Central alveolar ventilation, or what is better known as sleep apnea
  • High spinal cord paralysis in which the drive for respiration is still present but the injury to the spinal cord prevents stimulation from the phrenic nerves

These 2 conditions account for most cases of diaphragm pacing. [9, 10, 11]

Another, albeit rare, use of diaphragm pacing is to treat patients with intractable hiccups. The remaining group of patients in whom diaphragm pacing has been used consists of those with severe COPD. In these individuals, the hypoxic stimulation is diminished by administration of any amount of oxygen.

Diaphragm pacing is contraindicated for patients in whom the phrenic nerve is not functional. Such patients include those with severe traumatic injury to the nerve, those with nerve tumors, and most of those with neuropathies. In addition, diaphragm pacing is contraindicated for patients with conditions in which the diaphragm itself is not functional. Such conditions include myasthenia gravis, muscular dystrophy and advanced parenchymal lung disease.

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Technical Considerations

Compared with positive-pressure ventilation, diaphragm pacing has a number of advantages. A major advantage is that it allows a greater degree of independence. With diaphragm pacing, the patient is no longer isolated in a room, attached to a mechanical ventilator with an uncomfortable tube down the upper airways. Patients with central hypoventilation may be able to ambulate, go to work, travel, and perform most daily living activities. Portable diaphragmatic pacemakers are available that can be used for ambulatory monitoring of heart rate and rhythm.

Another major advantage is that diaphragm pacing affords the patient the ability to speak, which is impossible with an endotracheal tube in place. Once diaphragm pacing has been performed, the tracheostomy stoma can be plugged and speech resumed. For patients who are quadriplegic and on a ventilator, the speech capability made possible by diaphragm pacing is immensely desirable. [12, 13, 14, 15]

Moreover, diaphragm pacing, unlike endotracheal intubation, does not result in tracheal injury, tracheomalacia, tracheal stenosis, subglottic stenosis, tracheoesophageal fistula, or tracheitis. These problems are not trivial and can be life-threatening.

Furthermore, the extremely irritating copious secretions seen during mechanical ventilation are avoided. Patients on a ventilator are always at risk for death. The tubing may become kinked, coiled, obstructed, or even disconnected. The tracheostomy site may become plugged, or the ventilator may malfunction. All of these problems are avoided in patients undergoing diaphragm pacing. Patients who are quadriplegic have almost no way of correcting any of these problems if no attendant is available.

Whereas it is clear that diaphragm pacing can improve quality of life in patients for whom it is indicated, there is, as yet, little evidence to indicate that it improves survival in these patients. [16]

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Outcomes

Since the early studies on diaphragm pacing in the 1970s, data have been accumulated to show that the technique is effective and does help support ventilation in certain patient populations.

In the early days, the system utilized alternate-side pacing because bilateral high-frequency ventilation often caused rapid diaphragmatic fatigue. By the 1980s, however, continuous bilateral low-frequency stimulation of the preconditioned diaphragm for complete respiratory support was possible. [17, 18] Today, selected patients have the option for this surgery and are able to live a life of better quality.

There is no question that in selected patients diaphragmatic pacing can provide independence from a mechanical ventilator, communicate and have a better quality of life. However, long term outlook of all patients who have been managed with diaphragmatic pacing are not forth coming. The majority of studies are retrospective or case reports.

Some studies do report that patients can be paced for up to 20 years without much negative sequalae. However, the data are difficult to interpret because the methodology for follow up is different in many cases. Plus, there are no randomized studies or comparative groups. One should also remember that there is a selection bias for healthy patients and thus, generalizations to all patients cannot be made. Further, data on the postoperative course the methodology used to assess the patients vary from series to series. Even though there are 2 approved diaphragmatic pacing devices approved in the USA, there is no study to determine that one is better than the other. It should also be mentioned that just recently the second trial involving the NeuTx DPS system pacer for patients with ALS was halted and there is great concern that if the surgically implanted device—meant to improve breathing—was doing more harm than good.

There is no question that diaphragmatic pacing is beneficial to a select group of patients, but whether it is the panacea for all patients dependent on the ventilator remains to be seen. Given the increasing number of patients with sleep apnea and severe chronic obstructive pulmonary disease (COPD), diaphragm pacing may have a significant role to play in managing these conditions, at least during the night.

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Indications

Diaphragmatic pacing should be considered in the following groups of patients:

- Those with apnea from a central cause (the CNS lesion must be higher than C2,C3 since the phrenic nerve originates from the anterior horns of C3-5.

- Patients with amyotrophic lateral sclerosis and polio

- Patients with upper cervical spine injury

- Patients with central sleep apnea

- Patients with basilar meningitis, or brainstem infarction

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Contraindications

Diaphragm pacing is contraindicated for patients in whom the phrenic nerve is not functional. Such patients include those with severe traumatic injury to the nerve, those with nerve tumors, and most of those with neuropathies. In addition, diaphragm pacing is contraindicated for patients with conditions in which the diaphragm itself is not functional. Such conditions include myasthenia gravis, muscular dystrophy and advanced parenchymal lung disease.

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