The present invention concerns a medical pump comprising: a. A hard housing comprising a top (24) and bottom (1) hard shells, within which a rigid wall (3) and a movable membrane (2) create three distinct chambers； wherein i. said movable membrane tightly separates said second (29) and third (22) chambers ii. said first and third chambers have a watertight interface iii. said second chamber (29) is designed to contain a fluid iv. said first chamber (23) comprises a first venting mean (20) which is arranged to provide a fluidic communication between said first chamber (23) and the external environment； v. said third chamber (22) comprises a second venting mean which is arranged to provide a fluidic communication between said third chamber (22) and the external environment b. A pumping element (4) located in the first chamber (23) c. A least one pressure sensor which measure the pressure gradient between the first chamber (23) and the second chamber (29) d. A fluid pathway which permits: i. a first fluid connection (27) between said second chamber (29) and said pumping element ii. a second fluid connection (28) between said pumping element and a patient line (30).
