Due to its advantages like minimal trauma and a low risk of infections, the minimally invasive surgery (MIS) has become the standard operation technique for many surgical procedures. During this type of intervention, one of the main tasks from a technical point of view is the control of the pressure in the operation area in order to give the surgeon sufficient space to perform his actions. Because no invasive measurements are available, an extended Kalman filter incorporating the peristaltic behavior of the used medical device was developed to estimate the pressure in the operation area. This contribution focuses on the observer design while a separately designed PI controller using loop shaping was employed for validation. The proposed observer-based control structure was tested with a simulator deploying the principle of physical equivalence.