Abstract: A high-pressure packoff apparatus and method are disclosed. The packoff allows wireline entering a top drive drilling head through a top entry access system to be isolated in such a fashion to minimize the leakage and escape of drillstring fluids to the atmosphere. Optionally, an extension housing containing a flow tube assembly can be employed to accomplish the task. The flow tube assembly effectuates a pressure drop along the wireline conduit run therethrough, thus minimizing the likelihood of fluid escaping.