A shaft member and method of forming and using the same, wherein a portion of the external surface thereof is provided with a raised surface. A back panel is attached to the side panels by interfitting tabs and notches along adjacent edges of the back panel and the side panels. A correction coefficient memorizing circuit 7 memorizes the modified correction coefficient as shading correction coefficient data. In this case, the semiconductor chip, the connection elements and, partially, the circuit carrier are embedded in a plastic housing compound. The inlet end has an inlet opening submerged in the hydraulic fluid in the fluid reservoir. The controller identifies the signal patterns by using digital signal processing techniques to analyze the signals representative of breathing sounds.