A Closer Look: Diaphragm Pacing System

by Amy Madsen on Tue, 2012-01-03 09:49

For Pat Dwyer, this newly approved respiratory assist device means 'a life better lived,' but physicians urge caution until more is known

Illustration courtesy of Synapse Biomedical
Article Highlights:
  • In September 2011, the U.S. Food and Drug Administration approved the NeuRx Diaphragm Pacing System (DPS) for treatment of hypoventilation (inadequate breathing) in ALS.
  • The DPS doesn’t slow or stop the progression of ALS, but it may improve the quality of life. Pat Dwyer, of Kenmore, Wash., who has ALS, and his wife Jenny, have more than four years experience with the device, and believe it prolonged Pat's independence and mobility.
  • Related article Physicians Push for Proof of Diaphragm Pacer Benefit outlines concerns expressed by a number of MDA ALS physicians about the system.
  • People with ALS who are interested in the DPS should review all available information about the device and then discuss it with their physician.

Pat Dwyer of Kenmore, Wash., uses three different devices to make sure he’s getting enough air. A “sip-and-puff” ventilator supplements his breathing efforts during the day; bilevel positive airway pressure (BiPAP) helps him breathe at night; and the NeuRx Diaphragm Pacing System, or DPS, stimulates his diaphragm (the primary breathing muscle) 23 out of every 24 hours.

DPS unit attached to Pat Dwyer
The external wires attach to the orange toggle, which is then attached to the pacer cord. The cord attaches to the pacer unit. Dwyer carries it in his pocket.
Pat Dwyer
A “sip-and-puff” ventilator supplements Dwyer’s breathing efforts during the day.

Dwyer learned he has ALS in June 2005. His symptoms began in his left hand and traveled up his arm; the muscles in his right arm and hand were affected next, and then his diaphragm. He didn’t experience symptoms in his legs until 2009.

Dwyer rapidly lost the ability to breathe on his own and began using a Philips Respironics BiPAP in June 2007. But it wasn’t enough. Pat’s wife Jenny did an Internet search for “ALS and diaphragm” and found the NeuRx Diaphragm Pacing System.

About the DPS

The NeuRx Diaphragm Pacing System stimulates the respiratory diaphragm with electrical signals, by way of implanted electrodes. The system is designed to supplement breathing efforts and help preserve diaphragm muscle function.

In development for the past several years, in September 2011 the device received "humanitarian use" approval from the U.S. Food and Drug Administration for treatment of hypoventilation (inadequate breathing) in ALS. For more on the type of approval granted by the FDA, see Physicians Push for Proof of Diaphragm Pacer Benefit.

The approval means physicians can now prescribe the device, manufactured by Synapse Biomedical in Cleveland, for people with ALS. It also clears the way for insurance companies to cover part or all of the cost.

Although the DPS doesn’t slow or stop the progression of ALS, it may improve quality of life. That was what Pat and Jenny Dwyer were about to find out, as part of the clinical trial of the device.

Getting into the DPS clinical trial

In 2007, Jenny Dwyer called to inquire about an ongoing DPS clinical trial, and three months later she and Pat flew to the lead trial site in Cleveland. There, Pat underwent a series of tests, which he describes as “pretty easy,” to determine whether he met the criteria to participate in the study.

The entire battery of tests lasted between two and three hours and included:

  • FVC, or forced vital capacity, which measures the maximum amount of air one can breathe in and out;
  • blood carbon dioxide levels; and
  • the "sniff test," in which real-time observation of diaphragm movement is made using fluoroscopy (X-ray).

Because the results from the initial round of tests indicated that Pat had adequate preservation of his diaphragm and the phrenic nerves that stimulate it, he didn’t have to undergo separate phrenic nerve testing. (Phrenic nerve testing involves the use of various levels of electrical stimulation to different areas of the neck, and can be uncomfortable or even painful.)

Electrodes implanted via laparoscopic surgery

Pat met the criteria required to participate in the study. In December 2007, he and Jenny returned to Cleveland, where he underwent minimally invasive laparoscopic surgery to have five electrodes implanted in his diaphragm. At the time he received the implants, Pat’s FVC had declined to 52 percent; an FVC lower than 50 percent would have prevented him from having the surgery.

In laparoscopic surgery, gas is pumped into the abdominal cavity in order to give the surgeon room to maneuver. Afterwards, the gas has to be absorbed by the body and "that was a bit painful for Pat," Jenny says. "He said he felt like it was all pushing up under his shoulders and trying to come out his armpits!"

When Jenny visited Pat in the recovery room, he was awake and talking, but pretty loopy from the anesthesia, she says. But all his numbers were good, and the pacer was all hooked up and ready to go.

Instructions for using the pacer

The following day Pat and Jenny spent approximately an hour learning how to turn the pacer control unit on and off, how to change the battery, and how to hook up the external wires to the pacer. The toggle with the external wires slides into the corresponding holes in the pacer cord. It only fits one way, so there’s no chance of hooking things up incorrectly.

They learned that getting the exposed wires wet when bathing is "no big deal." While the area around the wires was healing, Pat kept it covered when showering. But now, Jenny says, "We just wash around it, and I’m careful when I dry it with a towel — just basically blot the wires dry."

Flying home with the pacer was no big deal either, as the wires didn’t even set off airport security scanners.

Because Pat was a participant in the DPS clinical trial, he traveled back to Cleveland at three, six and 12 months post-surgery for monitoring. FVC measurements and the sniff test were repeated at all appointments.

A 'shocking' sensation

Pat first started "pacing" only four hours a day.

"You can feel the DPS working," he says. "It feels like a low-voltage shock, but you soon get used to it and don’t really notice it anymore."

Pat slowly built up until he was using the DPS 20 to 23 hours a day. As the pacing time increased, he experienced a “sore-muscle” sensation in his abdomen but, as with the shocking sensation, he says he soon got used to it.

Pat says that when he began using the pacer, he felt less tired and lethargic at the end of the day, had more energy and didn’t need to nap as much as he had before.

But his FVC continued to decline, and he began using a sip-and-puff ventilator part time in September 2009.

"It was usually around three hours a day," Jenny notes. "Usually when he’d get home from work, he would ‘pump up’ with it before dinner." Since then, Pat has progressed to using the ventilator most of the day, in addition to the DPS.

Prolonged independence and mobility

Pat Dwyer

“It may be hard to jump through all the hoops,” says Dwyer, “but for us, the pacer was worth it.”

When Pat received the DPS he still was able to walk, "but if he’d had to start using the sip-and-puff in 2007, he would have had to start using a wheelchair as well — probably a year earlier than needed," says Jenny.

The wheelchair would have been required because the sip-and-puff vent weighs approximately 7 pounds and, says Jenny, "as much as I love my husband, I was not going to follow him around carrying his sip-and-puff!" The vent is now mounted on the back of Pat’s wheelchair.

The Dwyers believe the DPS helped Pat to continue running their business. (The couple owns two crab and salmon fishery boats in Alaska). The extra time without the wheelchair also made easier a family vacation to Hawaii (where Pat was able to hang out in the pool and ocean), travel to horse shows, and time spent on the boats.

Another thing the pacer enabled Pat to do was sleep in a bed again. Before he received the DPS, he slept in a recliner chair because lying flat made it too difficult to breathe. Once he began pacing full time during the night, he was able to sleep in a bed with two pillows — "a benefit for both of us!" Jenny says.

The quality of his sleep is better too, Pat says, because the pacer and his BiPAP work together.

The here and now … and the future

In December 2010, three years after he received the DPS, the pacer still was moving Pat’s diaphragm. "Not very much, and Pat had no movement on his own when the pacer was turned off, but there was still mechanical movement!" Jenny says.

Pat currently is dependent on his sip-and-puff ventilator during the day. He says the pacer works really well with both the sip-and-puff and his BiPAP and that there’s no sensation of the pacer “working against” either of the other two ventilation methods.

Although the couple has no way to tell whether the pacer is providing any benefit by keeping Pat’s diaphragm moving, Pat continues to use it.

"If he decides to stop using it," Jenny says, "we would simply turn the pacer off and not hook it up to him.

"While we know the pacer won’t stop the progression of the disease, we know that for us, it's made our life with the disease a life better lived!"

Getting a DPS

The DPS is not easily obtainable, and not everyone will qualify for the device. ALS disease progression may be too advanced in some for the device to provide benefit. Symptom progression also can make the required surgery too risky. Some physicians are calling for more evidence that the benefits of the device outweigh the surgical risks. Be sure to read Physicians Push for Proof of Diaphragm Pacer Benefit for more information.

Currently there are only three DPS treatment centers in the United States: University Hospitals of Cleveland (Ohio), Cedars-Sinai Medical Center in Los Angeles, and UT Southwestern Medical Center in Dallas. Another six centers provide referrals.

To view an interactive map containing locations and contact information, visit synapsebiomedical.com and in the "ALS Lou Gehrig’s" box click on "U.S. ALS Centers."

Amy Madsen
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