Diaphragmatic Pacing in Children
Breathing can be a challenge for children with medical conditions. There are many reasons for breathing issues but when breathing becomes ineffective, measures must be taken to ensure life and development. One reason for difficulty breathing concerns issues with the phrenic nerve. This is the nerve that is mainly responsible for pulling the diaphragm down to pull air into the lungs or inspiration. When the nerve relaxes, the air is expelled from the lungs as expirations occur. The phrenic nerve can be intact but not receive the correct messages from the brain to contract the diaphragm or miscommunication of messages along either or both tracts of the nerve.
The phrenic nerve is discussed as one nerve, but it is actually two nerves that act in unison. This nerve exits each side of the spinal cord at the cervical spinal levels of C3, C4 and C5. It travels down the neck, through the chest cavity along the inner sides of the lungs, finally reaching its goal of innervation of each side of the diaphragm. Interestingly, the diaphragm is also in two sections called the hemidiaphragm, but since they work together, the diaphragm is considered one muscle. One of the two separate phrenic nerves innervates one separate diaphragm section. Both diaphragms are considered one because they act in unison as controlled by the brain. Issues can be with one or both phrenic nerves, which impact one or both halves of the diaphragm. The right diaphragm is a bit stronger than the left as the liver protects it whereas the left diaphragm is formed, so it does not interrupt heart function.
Pediatric issues that can affect the phrenic nerve, which decreases diaphragm function, thereby decreasing respiration, are spinal cord injury from trauma or disease, especially at C3, C4, and C5, birth trauma, tumors, radiation therapy, congenital central alveolar hypoventilation syndrome (CCAHS), hypothalamic dysfunction, Chiari II malformation, myelomeningocele, cardiac surgery, and neuromuscular diseases such as muscular dystrophy, Hirschsprung’s disease, among others. Like other peripheral nerves, the phrenic nerve can be overstretched, compressed, ruptured, avulsed (torn), or by direct damage.
Testing of the phrenic nerve can be done by physical assessment of respiratory status, x-ray to visualize a static view of the diaphragm (one side elevated more than the other), or CT or MRI for timed movement of the diaphragm. Ultrasound assessment provides real-time images of the diaphragm in action and can be done at the bedside without sedation. Pulmonary function tests may be done for assessment of breathing effectiveness and lung fulling. For partial or mild phrenic nerve injury testing, the Sniff test may be done. In this test, the child is asked to breathe in, breathe, out, hold their breath, and sniff forcefully. Fluoroscopy of the diaphragm function is assessed during the maneuvers. Phrenic nerve stimulation tests include electric or magnetic stimulation to the phrenic nerve at the neck. The cause of diaphragm paralysis is determined if the phrenic nerve does not move the diaphragm when stimulated. The type of test used to assess the phrenic nerve is based on symptoms and condition. Most of these tests are used if the child is breathing on their own. They can be repeated to look for changes in breathing ability. If breathing is absent, the phrenic nerve stimulation test maybe completed.
If the phrenic nerve is not functioning to sustain adequate oxygenation in the body, different treatments are conducted as needed by condition. For weakened phrenic nerve function, therapies will be provided for muscle strengthening. Assistive breathing devices such as CPAP may be used to support breathing. If there is scaring around the phrenic nerve, it may be removed surgically, or a nerve graft might be inserted. Transferring a nerve within the body may assist with phrenic nerve function. Since the phrenic nerve is a peripheral nerve, electrical stimulation may be applied.
More severe cases of phrenic nerve dysfunction will require significant interventions. Typically, mechanical ventilation is initiated. For long-term use, this requires a tracheostomy with a connection to a ventilator that provides breathing. This treatment has been used for a number of years quite successfully. If your child has an issue with the phrenic nerve, you are familiar with this intervention. Children can thrive with this option.
As with all medical interventions, there are some downsides to mechanical ventilation. The most common complication is pneumothorax, or a hole in the sac that holds the lung allowing air to escape. Other physical issues include bronchopleural fistula or a connection between the bronchial tree in the lungs and the space around the lung, wound expansion around the tracheostomy site, and pneumonia. The sense of taste becomes diminished over time with mechanical ventilation. Speaking is dependent on the breath movement of the machine. Complications also include power outages supplying energy to the mechanical ventilator, accidental disconnections at the trachea site, difficulty in moving the child, challenges with dressing and other activities of daily living, and interrupted play. Finding caregivers or even babysitters is a challenge. In other words, mechanical ventilation can affect both child and parent quality of life.
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The benefits are that your child is able to live, can have a satisfying life, and thrives. Children who use mechanical ventilation do grow up to be successful adults.
As mentioned previously, research is generally conducted with adults and then moved to the pediatric realm. Success in providing ventilation is the development of diaphragmatic pacing. This technique has been around for a number of years but more recently has met mainstream. Advances in the technology of the device, the ability to implant the device using laparoscopic technique (minimally invasive) surgery and FDA approval have made this intervention available to most adults and children. This is one area where it appears that dramatic success in pediatric cases has enhanced the use in children faster than adults. It could be because a child's developing body is more adaptable or because people are more willing to move ahead with the process. Diaphragmatic pacing is now more often offered as the first option.
Two types of diaphragmatic pacers are commonly used. The Conventional type has an internal electrode attached to the phrenic nerve at the neck, chest, or diaphragm. A receiver is placed under the skin. A radiofrequency signaling transmitter is placed on the outside of the skin for control. The other type is called a Diaphragmatic Pacing System (DPS). In this system, four electrodes are placed on the diaphragm, with a fifth electrode implanted under the skin as a grounder. The five electrodes are grouped together in a socket exiting the skin as an external pulse generator that connects to an external, removable cable.
Some of the advantages of diaphragmatic pacing children include immediate implant without some of the testing for those eligible, resulting in less delay, use of the device as a bridge to rest an injured body until the return of function, a closed system preventing infection and internal lung damage, fewer options for equipment failure or disconnections, the ability to move more freely and less often use of a tracheostomy. Speech has a regular flow. Eating by mouth is possible with taste maintained. Depending on the individual case, the stimulation by the diaphragmatic pacer can ‘train’ the phrenic nerve to begin to work again as the nervous system attempts to heal itself. Some research studies suggest lifespan with the diaphragmatic pacer is significantly enhanced perhaps because it mimics typical ventilatory function, is implanted, so there is no artificial opening in the body once the implantation surgery has healed and/or because it triggers the natural movement and function of the diaphragm.
This is not to say that diaphragmatic pacing does not have its own downsides. The complications are rarer but can happen. Equipment can fail, the implant can become dislodged, wires can break internally. Surgical complications, as with any surgery, can occur, including infection, nerve damage, bleeding, or poor healing.
Many payors are seeing the advantage of using diaphragmatic pacing. Not only fewer complications but also in more comfort and freedom. Since this is a commercially available device, approved by the FDA, you can obtain the device anywhere. You do want a surgeon experienced in the implantation of children. Many trauma surgeons and pulmonary surgeons are implanting the device immediately to reduce and avoid the complications of mechanical ventilation. These same trauma surgeons and pulmonary surgeons are able to implant the device in non-emergent situations as well. You may be able to get the device in your hometown or close by. No longer would you need to travel or go out of state (as in the case of Medicaid payments).
Your child may already be using mechanical ventilation. Consideration of switching to diaphragmatic pacing is an option. Diaphragmatic pacing may be the only ventilatory method used, or you may opt for some alternatives. Some children and parents opt for a diaphragmatic pacer in the day with non-invasive mechanical ventilation at night. There are all sorts of combinations of the product that can benefit your child. The more you learn about diaphragmatic pacers, the more you will be able to make an informed decision for your child.