Recovery after Unilateral Phrenic Injury Associated with Coronary Artery Revascularization: Discussion (6)

Peripheral nerve growth rates have been shown to differ in the proximal and distal segments of a peripheral nerve ranging from 1 to 8 mm per day. Accurate regeneration rates have not been established for the phrenic nerve. The data from this study allow an approximation of the rate of recovery after injury during bypass surgery. Assuming that the injury occurs at the midpericardium, the length of the phrenic nerve to its entry of the diaphragmatic crus was estimated at 150 mm. The distance from the motor point to the area of muscle fibers adjacent to the recording site on the left has been previously measured at 28 mm. Given that the phrenic nerve first recovered around 200 days after bypass surgery, we estimate a regrowth rate of approximately 1 mm per day. This is obviously only a rough estimation, since both the exact site of injury and the precise time of recovery could not be ascertained. ventolin inhalers
In this study we demonstrated a progressive improvement in phrenic nerve function over 12 months after bypass surgery-associated paresis or paralysis. Phrenic nerve electrophysiologic studies were more sensitive in assessing this recovery than measurement of vital capacity or Pimax. Incomplete recovery, however, was commonly noted over the duration of the study either because of inadequate follow-up duration or because phrenic nerve injury was permanent. However, the residual unilateral phrenic nerve dysfunction was of little functional consequence in any of the patients in this study.