Pressure conditioning systems for supplying insufflation gas to an open-ended body conduit such as a rectal cavity during a transanal minimally invasive surgery (TAMIS) procedure can reduce billowing of walls of the body conduit. A pressure conditioning system can include a pressure storage component, an accumulator, and a flow restrictor. The pressure storage component can include a variable volume reservoir that is biased to a relatively low volume state. The flow restrictor can include insufflation tubing with a restrictor plate having a relatively low diameter orifice. The pressure storage component, accumulator, and flow restrictor can be fluidly connected in various orders in series or as side branches from a gas flow conduit. Despite a pulsed or otherwise discontinuous insufflation gas flow and leakage and absorption from the body conduit, the pressure conditioning system can maintain a constant pressure within the body conduit.