Figure 1: A mapping probe identifies the phrenic nerve motor point through qualitative visualization of diaphragm motion and quantitative measurement of the abdominal pressure to assess the strength of contraction.
Figure 2: Implantation of intramuscular diaphragm electrodes that are then directly connected to an external stimulator that delivers stimulus pulses and provides respiratory timing.
Surgeons with the divisions of Trauma and Gastrointestinal Surgery have performed the first diaphragm pacer implantation at Penn Medicine. This innovative procedure addresses chronic respiratory failure originating in traumatic or pathological interruption of the neural pathways that regulate breathing. For patients so affected, diaphragm pacing offers an alternative to mechanical ventilation for restoration of efficient breathing, and consequent significant improvement in quality of life.
Breathing is primarily an involuntary process originating in the motor cortex of the medulla, where among much else, neural impulses are issued to phrenic nuclei in the C3-C5 region of the cervical spine and travel from there along motor fibers of the phrenic nerves to innervate the diaphragm. The primary muscle of inspiration, the diaphragm is split into right and left hemispheres, each served by a phrenic nerve.
Among individuals with respiratory failure, a subset will have an intact respiratory system but lack efferent neural communication between the brain and muscles of the diaphragm via the phrenic nerves. Many of these patients (particularly those with cervical lesions at or above the C3 level) are ideally suited for diaphragm pacing therapy.
Diaphragm pacing is the general term for separate systems designed to either deliver electric impulses to the diaphragm peripherally via the phrenic nerves, or directly through electrode placement at the diaphragm (the latter system is presently employed at Penn Medicine). Considered equivalent in efficacy, the intent of both systems is to stimulate respiration sufficient to meet the body's basic metabolic demands. The systems require the phrenic nerves to be intact and the application of diaphragm reconditioning after implantation.
Case Study:
After incurring a cervical spinal cord injury in a car accident that left her tetraplegic and ventilator dependent, Mrs. M, a 54-year-old woman, was sent to Penn Presbyterian Medical Center and Good Shepherd Penn Partners to recover. Several months after her discharge to home, and concerned about the long-term implications of mechanical ventilation, she returned to the Department of Surgery at Penn Medicine for diaphragm pacer implantation. Seen by Jeremy W. Cannon, MD and Daniel Alejandro Hashimoto, MD, MTR, Mrs. M expressed her wish to proceed and her understanding of the relevant risks, benefits, and alternatives of the procedure.
DESCRIPTION OF PROCEDURE: Following standard preoperative preparations, Mrs. M's peritoneal cavity was accessed by laparoscopic supraumbilical vertical midline incision. The anterior and posterior phrenic nerve insertion sites were then located at the right and left hemidiaphragms, and suitable implantation locations identified on both sides. Following mapping involving a combination of inputs from the neurostimulator, abdominal pressure measurements and visual evidence to identify the motor point of the phrenic nerve (Figure 1), contraction of the diaphragm was confirmed. Both hemidiaphragms responded to stimulation, though the left responded somewhat less briskly than the right, and was noted to have some billowing, suggesting the possibility of pneumothorax or capnothorax. A chest x-ray performed at the completion of the procedure found no evidence of these events, however.
Using an implantation device, neurostimulator electrodes and pacing wires were then inserted into both hemidiaphragm sites (Figure 2) and a grounding wire at a separate location. Following re-confirmation of function, all wires were anchored in place and the incisions were closed and sealed.
Mrs. M tolerated the procedure well and was taken to the Trauma Surgical Intensive Care Unit in critical, but stable condition. Almost immediately after implantation, the team activated the pacemaker to begin the long process of diaphragm re-conditioning and ventilator liberation. Mrs. M did well through a short course at Penn Medicine and is now continuing her recovery with ongoing diaphragm conditioning at a local spinal cord rehabilitation center.
About the Services of the Divisions of Traumatology, Surgical Critical Care and Emergency Surgery and Gastrointestinal Surgery at Penn Medicine
The specialists at Penn Trauma Surgery and Penn GI Surgery collaborate on complex surgeries of the abdomen involving therapies for the sequelae of trauma, including major liver trauma, severe bowel injuries requiring complex reconstruction, pancreatic trauma, and now spinal cord injury with persistent respiratory failure .
Penn Trauma Surgery Team
Penn Gastrointestinal Surgery Team