Chronic respiratory failure requiring ventilatory support is usually caused by severe derangements in the function of the lungs, chest wall, and/or respiratory muscles. Mechanical ventilation is the only feasible option for most patients with these disorders. In certain patients, however, the function of the respiratory apparatus is completely intact except for lack of adequate nervous output from the respiratory centers in the medulla (central hypoventilation syndrome [CHS])1–3 or interruption of electrical signals from the medulla to the respiratory motoneurons in the spinal cord, which innervate the major inspiratory muscles (cervical spinal cord injury). These patients can be offered an alternative means of respiratory support by diaphragmatic pacing (DP), a more natural and physiologic form of breathing.3–12
Although straightforward in concept, DP required several significant scientific developments before becoming a clinically useful modality. A brief historical perspective provides some insight into the evolution of DP and understanding of its clinical utility.
It was more than two centuries ago that Caldani13 first observed that diaphragm movement could be achieved by electrical stimulation of the phrenic nerve in animals. In the first human demonstration (1818), Ure14 stimulated the phrenic nerve and restored breathing in a criminal immediately following execution. In the latter portion of the nineteenth century, the application of moistened sponges over the outer borders of the sternocleidomastoid muscles resulted in activation of the phrenic nerves, and this technique became an accepted method of restoring ventilation.15,16 Duchenne found phrenic nerve stimulation to be the best method of producing natural respiration17 and is credited to have placed electrophrenic stimulation on a solid physiologic foundation.18 In the 1940s, Sarnoff et al19,20 demonstrated that ventilation could be maintained in an acute setting in patients with bulbar poliomyelitis utilizing percutaneous electrodes. The lack of implantable devices that were safe and reliable, however, limited the long-term usefulness of DP to support ventilation. Consequently, the technique of phrenic nerve stimulation was supplanted by the development of the more reliable mechanical ventilators.
In the 1960s, the critically important work of Glenn et al resolved major technological issues, which led to the development and implementation of modern-day pacing systems.21–23 These investigators defined the appropriate patient selection criteria, preoperative assessment methodology, surgical methods including optimal electrode placement, and appropriate stimulation parameters necessary to achieve full-time ventilatory support.8–12,23,24 Further refinements to this early design were made by other investigators with regard to improved electrode design25,26 and less-invasive methods of electrode placement.27–30 As a consequence, DP has evolved into a safe and practical method of providing ventilatory support in select patient groups.
For patients requiring chronic ventilatory support, DP provides several advantages compared to mechanical ventilation (Table 62-1).5,6,11,31–35 Although the realized benefits of DP are ...