A sheath assembly for a probe comprises an internal sheath configured to isolate a probe from body fluids； and an external sheath circumferentially surrounding the internal sheath. The external sheath is configured to define at least one channel between said internal and external sheaths, for passing of fluids, tools or working tubes. The channel is collapsible, the channel is created by the annular space between the internal and external sheaths, the channel comprises a distal and proximal end, and the channel between said internal and external sheath is open at its distal end.
