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.