Diaphragm dysfunction an underdiagnosed condition and causes unexplained dyspnea. The dysfunction can range from partial weakness to complete paralysis of either one hemidiaphragm or both hemidiaphragm. Spinal cord injuries (SCI) and critical care polyneuropathies encompass a big chunk of the cases of diaphragmatic dysfunction. According to the National Spinal Cord Injury Statistics Center, the incidence of traumatic SCI in the United States was approximately 17,000 in 2016.
Diaphragmatic paralysis usually results from a high spinal cord injury, whereas mid-cervical lesions lead to partial weakness. SCI leads to chronic impairment and disability. Half of these patients develop tetraplegia, with 4% of these patients requiring long term mechanical ventilation. Critical illness polyneuropathy (CIP) is a common complication of critical illness affecting the motor and sensory neurons. Muscle involvement causing loss of muscle mass and eventual weakness has been referred to as critical illness myopathy. The involvement of the phrenic nerve and diaphragm leads to its weakness and, at times, complete paralysis. These patients have worse outcomes with prolonged weaning, higher hospital length of stays, and dependency on mechanical ventilation.
Traditional approaches to management have been mainly focused on waiting for recovery through innervation while supporting the patient on mechanical ventilation. However, this is fraught with complications. In the past few years, diaphragm pacing (DP) has been a proven therapy to wean SCI patients from mechanical ventilation (MV). A small feasibility study evaluating DP in critically ill mechanically ventilated patients demonstrated that the diaphragm could significantly help with the work of breathing when activated by a catheter-based, transvenous DP. A large multi-center randomized clinical trial (RESCUE 2) is underway to compare temporary transvenous diaphragm pacing vs. standard of care for weaning from mechanical ventilation.