membrane 2 which may be moved between a bottom hard shell 1 and the rigid wall 3 and comprises an upper face 8 a lower face 9 and a lateral face 10 said bottom shell 1 contains several holes 5 which are forming the internal ends of passages 7 communicating between the third chamber and the external environment the first chamber 23 is defined between the top hard shell 24 and the rigid wall 3 said first chamber 23 comprises an upper face 25 a lower face 26 a pumping element 4 and a first venting mean 20 the third chamber and the first chamber are tightly separated by at least said rigid wall 3 which is designed to form a watertight interface in one of said embodiments a hydrophobic surface treatment or coating can also be used on and or around the holes 5 to limit the water ingress in one of said embodiments said first chamber 23 comprises the electronic elements in one of said embodiments the lateral faces of said chambers are formed by the junction between part of the top and the bottom hard shell of the medical device the medical device comprises a first fluid connection 27 between said second chamber 29 and said pumping element and a second fluid connection 28 between said pumping element and the.