The present invention lessens the amount of air entering between mating membranes of a pressure sensor. The pressure sensor of the present invention includes a transducer portion and separate patient or medical fluid transfer portion or dome. The transducer portion is reusable and the dome is disposable. The dome defines a fluid flow chamber that is bounded on one side by a dome membrane. Likewise, the transducer is mounted inside a housing, wherein the housing defines a surface that holds a transducer membrane. The two membranes mate when the dome is fitted onto the transducer housing. The pressure sensor enhances the seal between the mated membranes by creating higher localized contact stresses. The pressure sensor also reduces the amount of gas that permeates from the fluid chamber across the dome membrane and between the interface by making the dome membrane from a material having a low vapor transmission.