Evaluation of Phrenic Nerve and Diaphragm Function with Peripheral Nerve Stimulation and M-Mode Ultrasonography in Potential Pediatric Phrenic Nerve or Diaphragm Pacing Candidates

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Key points

  • Combining phrenic nerve stimulation with observation of the movement of the hemidiaphragm with M-mode ultrasonography provides quantitative functional data in the setting of diaphragm paralysis.

  • Traditional phrenic motor nerve conduction studies such as electromyography of the diaphragm have limitations in predicting the success of phrenic nerve or diaphragm pacing.

  • Phrenic nerve pacing is an effective form of respiratory management in pediatric high cervical spinal cord injury.

  • Successful phrenic

Introduction: nature of the problem

A phrenic nerve pacing system consists of implanted receivers and electrodes, external antennas worn directly over the implanted receivers, and an external transmitter. The external transmitter and antennas send energy to the implanted receivers. The electrical stimulation is accomplished by transcutaneous radiofrequency stimulation of the implanted receivers by the external antennas. The implanted receivers receive the radiofrequency energy and convert it to electrical impulses, which directly

Diaphragmatic Ultrasonography

Diaphragmatic ultrasonography is performed with the patient in the supine position. For the older pediatric and adult patient, a multifrequency 4-MHz vector transducer is used in the longitudinal semicoronal plane using a subcostal or low intercostal approach extending from the midaxillary to the midclavicular lines. In young pediatric patients, a multifrequency 7-MHz vector transducer is used from the same approach. The right diaphragm is visualized through the window of the liver, and the

Case 1

J.O. sustained a C1 ASIA A spinal cord transection in a pedestrian versus automobile accident at 7 years of age with resulting complete diaphragm paralysis. He was initially ventilated with positive pressure via tracheostomy in the critical care setting. J.O. underwent bilateral phrenic nerve evaluations with transcutaneous nerve stimulation and diaphragmatic ultrasonography as described. A positive response was obtained and, 35 days following the injury, bilateral phrenic nerve pacers were

Discussion

Diaphragmatic paralysis can lead to inadequate breathing and chronic respiratory failure with requirement for ventilatory support. Assisted ventilation may be achieved by using positive pressure devices via tracheostomy or mask interfaces, negative pressure devices such as the iron lung or cuirass, or phrenic nerve and diaphragm pacing. Phrenic nerve or diaphragm pacing exists as a desirable modality for the treatment of chronic respiratory failure in the appropriate setting, owing to the

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