Feasibility of transesophageal phrenic nerve stimulation

Abstract

Background Every year, more than 2.5 million critically ill patients in the ICU are dependent on mechanical ventilation. The positive pressure in the lungs generated by the ventilator keeps the diaphragm passive, which can lead to a loss of myofibers within a short time. To prevent ventilator-induced diaphragmatic dysfunction (VIDD), phrenic nerve stimulation may be used. Objective The goal of this study is to show the feasibility of transesophageal phrenic nerve stimulation (TEPNS). We hypothesize that selective phrenic nerve stimulation can efficiently activate the diaphragm with reduced co-stimulations. Methods An in vitro study in saline solution combined with anatomical findings was performed to investigate relevant stimulation parameters such as inter-electrode spacing, range to target site, or omnidirectional vs. sectioned electrodes. Subsequently, dedicated esophageal electrodes were inserted into a pig and single stimulation pulses were delivered simultaneously with mechanical ventilation. Various stimulation sites and response parameters such as transdiaphragmatic pressure or airway flow were analyzed to establish an appropriate stimulation setting. Results Phrenic nerve stimulation with esophageal electrodes has been demonstrated. With a current amplitude of 40 mA, similar response figures of the diaphragm activation as compared to conventional stimulation with needle electrodes at 10mA were observed. Directed electrodes best aligned with the phrenic nerve resulted in up to 16.9 % higher amplitude at the target site in vitro and up to 6 cmH20 higher transdiaphragmatic pressure in vivo as compared to omnidirectional electrodes. The activation efficiency was more sensitive to the stimulation level inside the esophagus than to the inter-electrode spacing. Most effective and selective stimulation was achieved at the level of rib 1 using sectioned electrodes 40 mm apart. Conclusion Directed transesophageal phrenic nerve stimulation with single stimuli enabled diaphragm activation. In the future, this method might keep the diaphragm active during, and even support, artificial ventilation. Meanwhile, dedicated sectioned electrodes could be integrated into gastric feeding tubes.

Breath-by-breath comparison of a novel percutaneous phrenic nerve stimulation approach with mechanical ventilation in juvenile pigs: a pilot study

“…Up to now, in clinical use PNS has been mainly administered via surgical implantation of phrenic stimulators in patients suffering from central hypopnea syndrome or high spinal cord injuries 12 , 13 . However, in recent decades, several trans- or percutaneous as well as esophageal methods of electrical or electromagnetic phrenic nerve stimulation have been established and positively evaluated in animals and humans 14 – 19 . The unifying goal was to establish a minimally invasive, temporary PNS method that provides ventilatory support to critically ill patients 17 .…”

Closed‐loop parameter optimization for patient‐specific phrenic nerve stimulation

“…5 Methods such as trans-venous, 6,7 percutaneous, 8 and direct surgical 9,10 implantation of stimulation electrodes have shown some success, while other approaches such as specialized esophageal electrodes are in the early stages of development. 11 These methods are, however, limited by the need for specific technical skills for application and procedural risks due to their invasive nature.…”

“…By activating the phrenic nerve with electrical stimulation, the diaphragm is forced to contract, “exercising” it and potentially preserving its function in a manner analogous to the application of neuromuscular electrical stimulation to avoid muscle atrophy in patients in the intensive care setting 5 . Methods such as trans‐venous, 6,7 percutaneous, 8 and direct surgical 9,10 implantation of stimulation electrodes have shown some success, while other approaches such as specialized esophageal electrodes are in the early stages of development 11 . These methods are, however, limited by the need for specific technical skills for application and procedural risks due to their invasive nature.…”