the apparatus for fetal scalp blood sampling schematically illustrated in fig1 through 3 b consists essentially of a tubular - shaped shaft 1 , a blade 2 that can be slid in the axial direction of the shaft 1 and that is mounted in the distal end of the shaft 1 , and a blood collection device 3 positioned on the distal end of the shaft 1 . as can be seen in fig1 b , 3 a , and 3 b , the blade 2 is replaceably mounted in a blade holder 4 , which is mounted in the shaft 1 so that it can slide by means of a positioning mechanism 5 in the axial direction of the shaft 1 . in the illustrated embodiment , the blade holder 4 is configured in jaw - like shape in such a way that the distal end of the blade holder 4 comprises a rigid base body 4 a that contains and stores the blade 2 as well as a cap 4 b that can be rotated with respect to the rigid base body 4 a . in the change - over position shown in fig3 a the blade holder 4 has been pushed by means of the positioning mechanism 5 out of the shaft 1 on the distal side until the cap 4 b of the blade holder 4 can be flapped out from the rigid base body 4 a in order to remove an old blade 2 and to position a new blade 2 in the blade holder 4 . as can be seen in fig1 b , 2 a , 2 b , as well as 3 a and 3 b , the blade 2 is always positioned in the blade holder 4 in such a way that the distal point of the blade 2 extends beyond the distal end of the blade holder 4 . the distance by which the blade 2 extends beyond the distal end of the blade holder 4 corresponds to the depth of incision of the blade 2 during removal of blood . the protrusion of the blade 2 and thus the incision depth of the blade can be adjusted by corresponding positioning of the blade 2 in the blade holder 4 by means of stops in the blade holder 4 . the positioning mechanism 5 , by which the blade holder 4 equipped with the blade 2 can be slid in the axial direction of the shaft 1 inside the shaft 1 , consists in the illustrated embodiment of a push - button 7 that can be slid in a guide track 6 configured in the shaft 1 . as can be seen by juxtaposing the side views and overhead views of fig1 a and 1 c , 2 a and 2 b , and 3 a and 3 b , the guide track 6 is essentially of u - shaped configuration with two limbs running parallel in the axial direction of the shaft 1 , so that the open diameter of the guide track 6 is of enlarged configuration at three points , that is , first at the two free ends , which are distal with respect to the entire instrument , of the parallel limbs of the u - shaped guide track 6 , and then at a bend in the transition from the perpendicular base of the u - shaped guide track 6 to one limb . these three positions with enlarged guide track diameter mark end positions of the blade holder 4 and thus of the blade 2 with respect to its position to the shaft 1 . in the starting position shown in fig1 a through 1 c , the blade holder 4 is inserted by means of the positioning mechanism 5 into the shaft 1 until the blade 2 is completely inside the shaft 1 and no risk of injury can result from the blade 2 protruding on the distal side beyond the blade holder 4 . the corresponding end position of the push - button 7 is the position in the transition from the perpendicular base of the u - shaped guide track 6 to one limb , that is the position of the push - button 7 mounted farthest from the proximal end of the shaft 1 . to be able to conduct the blade holder 4 by axial pushing , on the one hand , into the working position and , on the other hand , into the change - over position , the two parallel limbs of the u - shaped guide track 6 are configured with differing lengths . the blade holder 4 is conducted into the working position by pushing the push - button 7 to the end of the short limb . in this position the blade holder 4 and the point of the blade 2 protrude beyond the distal end of the shaft 1 far enough so that pressing the apparatus against the head skin of the patient leads to insertion of the blade point into the head skin . the change - over position shown in fig3 a and 3 b , in which the push - button 7 of the positioning mechanism 5 is found at the end of the long limb of the u - shaped guide track 6 , differentiates itself from the working position in that the blade holder 4 has clearly been pushed out of the distal end of the shaft 1 by means of the positioning mechanism 5 through the working position until the cap 4 b of the blade holder 4 can be opened to replace the blade 2 . to ensure that the blade holder 4 and thus also the blade 2 are secured in the particular end position and the push - button 7 cannot be pushed accidentally , the contours of the guide track 6 and of the push - button shaft are attuned to one another in such a way that the push - button 7 is positioned in the guide track 6 so that it cannot slide in the various end positions of the blade holder 4 . for this purpose the shaft of the push - button 7 comprises a thickening , which corresponds exactly with the thickening of the guide track diameter in the area of the end positions . in this position , in which the thickened area of the push - button shaft is inserted in the enlarged guide track diameter , mere lateral pushing of the push - button 7 is no longer possible . an additional pushing of the push - button 7 is possible only when the push - button is pressed downward inside the guide track 6 until the thickened area moves out of engagement with the guide track 6 . unintentional actuation of the positioning mechanism 5 is further prevented in that the push - button 7 can be pressed against the force of at least one spring - elastic element 8 into the guide track 6 . this spring force acting on the push - button 6 thus , on the one hand , prevents an unintentional pushing of the push - button 6 by lateral impact and , on the other hand , ensures that the push - button 6 is pre - tensed in the individual slide - proof end positions . as can be seen from fig4 , the spring - elastic element 8 that pre - tenses the push - button 6 is configured in the illustrated embodiment in such a way that the shaft of the push - button 6 is positioned on a base plate 9 , which is supported by two spring elements 10 on a push - pull rod 11 of the positioning mechanism 5 . as can further be seen in particular from the side views in fig1 a , 2 a , and 3 a , the blood collecting apparatus 3 in the illustrated embodiment consists of a capillary tubule 12 that can be exchangeably secured laterally on the distal end of the shaft 1 and that imbibes the blood sample by capillary action . to ensure , even under spatially cramped conditions , that there is sufficient illumination of the operating area at all times , a light conductor 13 is positioned as well in the shaft 1 , said conductor extending as far as the distal end and illuminating the operating area in the immediate vicinity of both the blade 2 and the capillary tubule . the second embodiment of the apparatus for fetal scalp blood sampling , illustrated in fig5 , is distinguished from the previously described embodiment in that the same light conductor 13 or an additional light conductor 13 comprises a light emission aperture 14 , by which the proximal end of the capillary tubule 12 can also be illuminated . this additional illumination of the proximal end of the capillary tubule 12 is advantageous for the user because in this way the operator can determine whether an amount of blood sufficient for the following examinations has been incorporated into the capillary tubule 12 on the strength of the active capillary forces . an apparatus of this configuration for fetal scalp blood sampling is distinguished in that the apparatus is configured as a reusable instrument because of the replaceability of the blade 2 . for this purpose the apparatus should of course be configured with corresponding choice of materials and insulating measures so that the apparatus can be completely dismantled and autoclaved for cleaning purposes . an additional advantage of the present apparatus consists in the fact that the blade 2 can be converted by means of the positioning mechanism 5 into defined and fixable end positions that ensure a high degree of operating safety .
the invention relates to an apparatus for fetal scalp blood sampling , having a shaft , a blade that is mounted removably in the distal end of the shaft and that can be slid by means of a positioning mechanism between a starting position mounted in the and a working position extending beyond the distal end of the shaft , and also having a blood sampling device mounted on the distal end of the shaft . to create an apparatus for fetal scalp blood sampling that is easy to operate and also ensures a high degree of operating safety , it is proposed with the invention that the blade can be fixed by the positioning mechanism in the respective end position .