JP7563107B2 - Pressure Measurement Chamber - Google Patents

Description

The present invention relates to a pressure measurement chamber that is installed on a blood circuit.

Dialysis is a treatment in which blood drawn from the patient is introduced into a dialyzer, where unnecessary components in the blood are replaced with useful components in the dialysis fluid and filtered, and the treated blood is returned to the patient. In this type of dialysis, blood pressure is measured at various points in the blood circuit through which the blood flows to prevent damage to useful blood cells and blood coagulation.

The pressure measurement chamber disclosed in Patent Document 1 is known as a device for measuring the pressure of blood flowing through a blood circuit. This pressure measurement chamber includes a housing having an internal cavity and a flexible membrane that separates the cavity into a blood chamber and an air chamber.

JP 2019-63439 A

Dialysis is generally performed intermittently over several days at a specified flow rate (e.g., about 200 mL/min). On the other hand, for patients whose liver function has suddenly deteriorated, a dialysis treatment called CRRT (Continuous Renal Replacement Therapy) may be performed, in which the treatment is performed continuously for several hours at a lower flow rate (e.g., about 80 mL/min). However, there are currently no pressure measurement chambers suitable for CRRT, and the pressure measurement chambers used in general dialysis are also used in the blood circuits for CRRT.

Therefore, the objective of this disclosure is to provide a pressure measurement chamber suitable for a blood circuit in which blood flows at a low flow rate.

The pressure measurement chamber according to the present disclosure comprises a housing having a chamber space partitioned by a flexible membrane into a blood side chamber and an air side chamber, an inflow port through which blood flows into the blood side chamber, and an outflow port through which blood flows out of the blood side chamber, and when the maximum area of a cross section perpendicular to the blood flow direction in the space of the chamber space occupied by the blood side chamber is defined as the maximum chamber space area A, and the opening area of the inflow port is defined as the inflow port area B, the area ratio A/B is 26.0 or less and 6.0 or more.

This makes it possible to realize a pressure measurement chamber in which blood is less likely to stagnate and blood is less likely to aggregate, even with a low blood flow rate. That is, as described in detail below, the inventors' intensive research has revealed that, compared to configurations in which the area ratio A/B is greater than 26.0, the tendency for the proportion of the area on the inner surface of the case where the shear stress is equal to or less than a predetermined value to decrease with a decrease in the area ratio A/B is more pronounced in configurations in which the area ratio A/B is 26.0 or less. Therefore, by using the above-mentioned configuration, it is possible to efficiently realize a small-capacity pressure measurement chamber in which blood is less likely to stagnate. In addition, by making the area ratio A/B 6.0 or more, it is possible to realize a pressure measurement chamber that can withstand practical use in dialysis treatments such as CRRT as a pressure measurement range.

The area ratio A/B may be 22.6 or less and 18.5 or more.

This makes it possible to realize a more preferable pressure measurement chamber from the viewpoint of suppressing blood coagulation at low flow rates and ensuring an appropriate pressure measurement range.

The pressure measurement chamber according to the present disclosure also includes a housing in which a blood side case and an air side case are joined together to form a chamber space, and the chamber space is divided into a blood side chamber and an air side chamber by a flexible membrane, and at least the inner surface of the air side case is provided with a protrusion that receives an ejector pin when demolding during injection molding.

This makes it possible to prevent damage to the molded product when the housing is made smaller to accommodate a low blood flow rate, and then the case is injection molded and then pressed with an ejector pin to release it from the mold. In other words, for a housing with a large capacity, the allowable deformation amount that can be tolerated when pressed by the ejector pin is large, but for a housing with a small capacity, the allowable deformation amount is small, so there is concern that the housing may be damaged by being pressed by the ejector pin during release from the mold. In contrast, the above-mentioned configuration improves strength with the protrusions that receive the ejector pins, preventing damage during release from the mold.

In addition, a rib may be provided on the inner surface of the air side case to form an air passage between the flexible membrane and the inner surface, and the protruding dimension of the convex portion may be equal to or smaller than the protruding dimension of the rib.

As a result, when the flexible membrane bends toward the air side chamber, the flexible membrane will not come into contact with the end face of the convex portion before the rib. This prevents the convex portion from limiting the amount of bending of the flexible membrane, which would result in a reduction in the volume of the blood side chamber.

The inner surface of the air side case may be concave, and the end surface of the protrusion may also be concave.

When the inner surface of the air side case is concave, making the end face of the convex part flat will increase the dimension of the protrusion into the chamber in some parts compared to a configuration in which the end face of the convex part is concave. Therefore, by making the end face of the convex part concave as described above, it is possible to suppress the partial increase in the dimension of the protrusion and prevent the volume of the blood side chamber from becoming smaller.

The pressure measurement chamber according to the present disclosure can realize a pressure measurement chamber suitable for a blood circuit in which blood flows at a low flow rate.

FIG. 1 is an exploded perspective view of a pressure measuring chamber according to the present embodiment. FIG. 2 is an exploded cross-sectional view of the pressure measuring chamber taken along line II-II in FIG. FIG. 3 is a cross-sectional view of the pressure measuring chamber shown in FIG. 2 when assembled. FIG. 4 is a graph showing the results of a simulation analyzing the shear stress on the inner surface of the pressure measurement chamber. FIG. 5 is a bottom view of the air side case as viewed from below. FIG. 6 is a cross-sectional view of the air side case taken along line VI-VI in FIG.

[Overall configuration of pressure measurement chamber]
1 to 3, pressure measurement chamber 100 according to the present disclosure includes a housing 1 in which a blood side case 2 and an air side case 3 are joined together to form a chamber space 11, and this chamber space 11 is divided into a blood side chamber 12 and an air side chamber 13 by a flexible membrane 4. In addition, blood side case 2 is provided with an inflow port 5 through which blood flows into blood side chamber 12, and an outflow port 6 through which blood flows out of blood side chamber 12. In addition, flexible membrane 4 is shown diagrammatically by a dashed line in FIG.

This pressure measurement chamber 100 has a generally egg-shaped exterior, as will be described in detail later, and its position during use is not particularly limited. However, for ease of explanation, the air side case 3 is considered to be above the blood side case 2, and the opposite direction is considered to be below. Also, the inlet port 5 is considered to be forward relative to the outlet port 6, and the opposite direction is considered to be backward. Furthermore, the direction that intersects both the up-down direction and the front-to-back direction is considered to be the left-to-right direction when facing forward.

In this embodiment, the pressure measurement chamber 100 is exemplified by a configuration suitable for use in CRRT, which processes blood at a low flow rate (e.g., about 80 mL/min) during dialysis treatment. In this case, the volume of the chamber space 11 is typically 3000 ^mm3 or less, and more preferably 2700 mm3 or less. However, the volume of the chamber space 11 is not limited to this, and the volume may be greater ^than 3000 ^mm3 as long as it satisfies the area ratio A/B described below.

The blood side case 2 includes a case body 20 to which an inflow port 5 and an outflow port 6 are connected. The case body 20 has an opening 21 that opens upward and an inner surface 22 that is recessed downward, forming a lower chamber space 11a that is the lower half of the chamber space 11. When the lower chamber space 11a is viewed in a plan view along the vertical direction (i.e., the shape of the opening 21), it has an elliptical shape with a major axis in the front-to-back direction and a minor axis in the left-to-right direction. When the lower chamber space 11a is viewed from the front along the front-to-back direction, it has a lower semicircular shape that is the shape of a perfect circle divided into two equal parts vertically.

A circumferential groove 23 is formed in the opening 21 of the case body 20 so as to surround the outside of the upper end portion of the inner surface 22. A circumferential wall 24 is erected on the outside of the circumferential groove 23, extending upward so as to surround the outside of the circumferential groove 23. As described below, the flexible membrane 4 is supported in the circumferential groove 23, and the air side case 3 is fitted onto the circumferential wall 24.

An inflow port 5 is connected to the front of the case body 20. The inflow port 5 is tubular, and its internal inflow passage 5a is connected to the lower chamber space 11a inside the case body 20. An outflow port 6 is connected to the rear of the case body 20. The outflow port 6 is tubular, and its internal outflow passage 6a is also connected to the lower chamber space 11a. The inflow passage 5a and outflow passage 6a are coaxial with each other.

A groove 25 extending in the front-to-rear direction is formed at the bottom of the inner surface 22 of the case body 20. This groove 25 extends from the connection point of the inlet port 5 to the connection point of the outlet port 6. Therefore, the opening 5b in the inlet passage 5a that communicates with the lower chamber space 11a is located at the front of the groove 25, and the opening 6b in the outlet passage 6a that communicates with the lower chamber space 11a is located at the rear of the groove 25. The portion of the groove 25 that extends from the front to the rear curves downward to fit along the inner surface 22 of the case body 20.

Here, the inflow passage 5a and the opening 5b have the same diameter, and the outflow passage 6a and the opening 6b also have the same diameter. In this embodiment, the inflow passage 5a and the outflow passage 6a also have the same diameter. As shown in FIG. 2, the inflow port 5 has an enlarged port connection port 5c in front of the inflow passage 5a, and the outflow port 6 has an enlarged port connection port 6c in the rear of the outflow passage 6a.

The air side case 3 includes a case body 30, to which the pressure detection port 7 is connected. The case body 30 is generally dome-shaped, has an opening 31 that opens downward, and has an inner surface 32 that is recessed upward, forming the upper chamber space 11b, which is the upper half of the chamber space 11. The shape of the upper chamber space 11b when viewed from above in the vertical direction (i.e., the shape of the opening 31) is an ellipse with a long axis in the front-to-back direction and a short axis in the left-to-right direction, similar to the opening 21 of the case body 20 of the blood side case 2 described above. In addition, the shape of the upper chamber space 11b when viewed from the front in the front-to-back direction is the upper semicircular shape when a perfect circle is divided into two equal parts vertically. Therefore, the chamber space 11 formed by joining the blood side case 2 and the air side case 3 from above and below has a perfect circular shape when viewed from the front.

A circumferential surface 33 is formed at the opening 31 of the case body 30, expanding in the radial direction from the lower end of the inner surface 32 and going around the opening 31. A circumferential wall 34 is vertically attached to the outside of the circumferential surface 33, extending downward so as to surround the outside of the circumferential surface 33. Furthermore, on the inside of the circumferential wall 34 on the circumferential surface 33, a claw portion 35 protruding downward is provided so as to go around the opening 31 along the circumferential surface 33. As described below, the circumferential surface 33 supports the flexible membrane 4 from above, and the circumferential wall 34 fits around the blood side case 2.

The pressure detection port 7 is connected to the front of the case body 30. The pressure detection port 7 is tubular and extends upward from the outer surface of the case body 30 with its axis pointing in the vertical direction. The internal passage 7a of the pressure detection port 7 communicates with the upper chamber space 11b inside the case body 30 at the opening 7b at its lower end. In addition, multiple linear ribs 50 are formed on the inner surface 32 of the case body 30 to form an air flow path between the inner surface 32 and the flexible membrane 4, and multiple protrusions 60 are formed to receive the ejector pins when the air side case 3 is released from the mold during injection molding. These ribs 50 and protrusions 60 will be described later with reference to Figures 4 and 5.

The flexible membrane 4 is a diaphragm with moderate flexibility, and displaces up and down toward the blood side chamber 12 or toward the air side chamber 13 depending on the pressure of the blood flowing through the blood side chamber 12. The flexible membrane 4 is roughly dome-shaped like the case body 30 (inner surface 32) of the air side case 3, and has a membrane body 40 and a flange 41. The membrane body 40 is recessed upward so as to open downward, and has an elliptical shape with a long axis in the front-to-back direction and a short axis in the left-to-right direction in a plan view. The membrane body 40 also has a lower surface 42 and an upper surface 43, and has an upper semicircular arc shape when a perfect circle is divided into two equal parts above and below in a front view. The flange 41 is extended from the lower end portion of the membrane body 40 in the radial direction and around the opening portion. In addition, a protrusion 44 protruding downward from the outer periphery of the flange 41 is provided so as to go around the flange 41.

The pressure measurement chamber 100 according to the present disclosure is constructed by combining the housing 1 consisting of the blood side case 2 and air side case 3 as described above, and the flexible membrane 4. That is, first, the flexible membrane 4, which is recessed upward, is assembled from above to the blood side case 2, which has the opening 21 facing upward. At this time, the protrusion 44 of the flexible membrane 4 is fitted inside the peripheral groove 23 of the blood side case 2. Next, the air side case 3 is assembled from above to the blood side case 2 in this state, with the opening 31 facing downward. At this time, the peripheral wall 34 of the air side case 3 is fitted externally onto the peripheral wall 24 of the blood side case 2. Also, the claw portion 35 of the air side case 3 is hermetically abutted against the upper surface of the flange 41 of the flexible membrane 4 so as to bite into it.

In this way, the blood side case 2, the air side case 3, and the flexible membrane 4 are bonded or welded to each other. As a result, a chamber space 11 is formed inside the housing 1, and this chamber space 11 is divided into a blood side chamber 12 and an air side chamber 13 by the flexible membrane 4. More specifically, the blood side chamber 12 is formed so as to be surrounded by the inner surface 22 of the blood side case 2 and the lower surface 42 of the flexible membrane 4, and the air side chamber 13 is formed so as to be surrounded by the inner surface 32 of the air side case 3 and the upper surface 43 of the flexible membrane 4. Since the thickness dimension of the membrane body 40 of the flexible membrane 4 is small, the volume of the blood side chamber 12 and the volume of the chamber space 11 are approximately the same.

In addition, the chamber space 11 at this time has a substantially elliptical shape when viewed from above and below, a substantially elliptical shape when viewed from the left and right, and a substantially perfect circle when viewed from the front and rear. In other words, the chamber space 11 has a substantially egg-like or rugby ball-like shape.

As described above, the flexible membrane 4 is dome-shaped and recessed upward, similar to the inner surface 32 of the air-side case 3. Therefore, when the pressure measurement chamber 100 is in an unused state, the membrane body 40 of the flexible membrane 4 is located unevenly in the upper chamber space 11b, and its upper surface 43 is located close to the inner surface 32 of the air-side case 3.

[Regarding area ratio]
Referring to Figure 3, in the pressure measurement chamber 100 according to the present disclosure, when the maximum area of a cross section perpendicular to the blood flow direction in the space occupied by the blood side chamber 12 in the chamber space 11 is defined as the chamber space maximum area A, and the opening area of the inflow port 5 is defined as the inflow port area B, the area ratio A/B is configured to be within a predetermined range.

More specifically, in this pressure measurement chamber 100, the internal space of the blood side chamber 12 is roughly egg-shaped like the chamber space 11, so when viewed in a cross section perpendicular to the blood flow direction (front-to-back direction), the area is maximum at the center in the front-to-back direction. Therefore, the area of the part indicated by the double arrow with the symbol A in Figure 3 is the maximum chamber space area A. On the other hand, in the inflow port 5, the inflow passage 5a and the opening 5b have the same diameter, so the inflow port area B is the area of the part indicated by the double arrow with the symbol B in Figure 3. Note that if the diameter of the inflow passage 5a is not constant, such as gradually decreasing or increasing, the area of the part of the inflow passage 5a where the flow path area is smallest can be taken as the inflow port area B.

For these areas A and B, the pressure measurement chamber 100 according to the present disclosure is configured so that the area ratio A/B is 26.0 or less and 6.0 or more, and more preferably, the area ratio A/B is 22.6 or less and 18.5 or more. This makes it possible to realize a pressure measurement chamber 100 in which blood is less likely to stagnate and blood is less likely to aggregate in the blood side chamber 12, even with a low blood flow rate.

Figure 4 is a graph showing the results of a simulation analyzing the shear stress on the inner surface of the pressure measurement chamber. The graph plots black filled diamond-shaped dots M1 and white filled diamond-shaped dots M2, with dots M1 corresponding to the simulation results for the pressure measurement chamber 100 of this embodiment.

In the graph of Fig. 4, the horizontal axis represents the area ratio A/B described above. In the graph of Fig. 4, the vertical axis represents the ratio of the region where the shear stress is 100 [s ^-1 ] or less to the total surface area of the evaluation target, expressed as a percentage. The total surface area of the evaluation target is the area defining the blood side chamber 12 of the pressure measurement chamber 100, and is equal to the sum of the area of the inner surface 22 of the blood side case 2 and the area of the lower surface 42 of the membrane body 40 of the flexible membrane 4. In the area ratio A/B in this simulation, the area B is kept constant, and the area A is used when the shapes of the case bodies 20 and 30 of the housing 1 are changed in size to be similar.

4, when the area ratio A/B is 26.0 or less, the proportion of the region with a shear stress of 100 [s ^-1 ] or less decreases more significantly with decreasing area ratio A/B than when the area ratio A/B is greater than 26.0. Therefore, by setting the area ratio A/B to 26.0 or less, a small-capacity pressure measurement chamber in which blood is less likely to accumulate can be efficiently realized.

In addition, the area ratio A/B is preferably 6.0 or more. That is, for the purpose of monitoring the blood pressure during dialysis treatment, the lower limit of the pressure that can be measured by the pressure measurement chamber 100 is determined. Then, the lower limit of the volume of the blood side chamber 12 is obtained from Boyle's law regarding the total volume and internal pressure of the air side chamber 13 and the pressure measurement transducer. Once the lower limit of the volume of the blood side chamber 12 is obtained, the maximum chamber space area A of the pressure measurement chamber is obtained. Here, when the pressure measurement chamber 100 measures negative pressure, -300 [mmHg] is exemplified as the necessary lower limit, and in that case, the above area ratio A/B is 6.0 or more. Therefore, for the convenience of the pressure measurement range, the area ratio A/B is preferably 6.0 or more.

4, as the area ratio A/B decreases and passes 18.0, the tendency for the percentage of the region where the shear stress is 100 [s ^-1 ] or less to decrease becomes gentler. Therefore, from the viewpoint of efficiently suppressing blood retention, it is more preferable that the lower limit of the area ratio A/B be 18.0 or more.

Furthermore, from the viewpoint of practical balance between the effect of suppressing blood stagnation and the pressure measurement range, it is preferable to configure the area ratio A/B to be in the range of 22.6 or less and 18.5 or more.

The above-mentioned preferable numerical range of the area ratio A/B is not limited to the pressure measurement chamber 100 having the configuration exemplified in Figures 1 to 3. For example, it also applies to a pressure measurement chamber having a spherical chamber space as disclosed in JP 2019-198454 A. The dots M2 shown in Figure 4 represent a simulation of such a spherical chamber space, and it can be seen from this that even in a configuration in which the chamber space is spherical, when the area ratio A/B is 26.0 or less, the tendency for the proportion of the region in which the shear stress is 100 [s ^-1 ] or less to decrease with the decrease in the area ratio A/B becomes more pronounced.

In this way, at least for those in which the chamber space is egg-shaped (or rugby ball-shaped) or spherical, and the flexible membrane forming the diaphragm is dome-shaped in an unused state and unevenly distributed in the upper chamber space, the above-mentioned effects can be obtained by configuring the area ratio A/B to be 26.0 or less. In this embodiment, as described above, the thickness of the membrane body 40 of the flexible membrane 4 is very small, and the blood side chamber 12 and the chamber space 11 have approximately the same volume. In such cases, the chamber space 11 may be used approximately instead of the blood side chamber 12 as the target space for the chamber space maximum area A.

[Ribs and protrusions]
Fig. 5 is a bottom view of the air side case 3 as viewed from below. Fig. 6 is a cross-sectional view of the air side case 3 cut along line VI-VI in Fig. 5, including partial enlarged views of the rib 50 and the protrusion 60. As shown in Fig. 5, a resin reservoir 36 is formed in the center of the air side case 3. That is, a recess is formed in the mold to increase the capacity of the inlet portion of the mold so that the molten resin flowing in from the gate during injection molding can flow smoothly into the inside. The resin reservoir 36 is formed by the resin stored in this recess solidifying, protruding inward from the air side case 3.

The resin reservoir 36 is circular in bottom view, and linear ribs 50 extend radially from the outer periphery. In this embodiment, eight ribs 50 are provided, and are arranged at approximately equal intervals (approximately every 40 to 45 degrees) around the resin reservoir 36. One end 51 of each rib 50 in the longitudinal direction is located close to the resin reservoir 36, and the other end 52 reaches close to the opening 31. The other end 52 of one of the ribs 50A reaches close to the opening 7b of the pressure detection port 7. Furthermore, as shown in an enlarged portion in FIG. 6, the cross section of the rib 50 that intersects the longitudinal direction is arc-shaped, and the height dimension (protruding dimension) H1 from the inner surface 32 of the air side case 3 is approximately constant over the entire length.

When the blood pressure in the blood side chamber 12 increases, such ribs 50 prevent the upper surface 43 of the membrane body 40 of the flexible membrane 4 from contacting the inner surface 32 of the air side case 3 without any gaps, and ensure a space for air to flow between the upper surface 43 and the inner surface 32. The height dimension H1 of the rib 50 is, for example, 0.2 mm, but is not limited to this and may be greater than 0.2 mm or less than 0.2 mm.

In addition, two protrusions 55 are provided near the opening 7b of the pressure detection port 7. These protrusions 55 are located on an extension of the above-mentioned rib 50A, and are arranged on either side of the opening 7b. These protrusions 55 have a height dimension larger than that of the rib 50, and in this embodiment, for example, is 0.3 mm. Providing such protrusions 55 makes it possible to prevent the opening 7b from being blocked by the flexible membrane 4.

5, a convex portion 60 is provided between adjacent ribs 50. At least some of the multiple convex portions 60 are arranged symmetrically with respect to the center of the air side case 3. The convex portion 60 receives an ejector pin during demolding in injection molding, and is pressed by the tip of the ejector pin during demolding. The convex portion 60 has a circular shape (perfect circle) when viewed from the bottom. The end face 61 (lower face) of the convex portion 60 has a concave shape. More specifically, the end face 61 of the convex portion 60 has a concave shape so as to follow (match) the inner face 32 of the air side case 3. The height dimension (protruding dimension) H2 of the convex portion 60, that is, the height dimension H2 from the inner face 32 to the end face 61, is a constant value. Furthermore, the height dimension H2 of such a convex portion 60 is configured to be equal to or less than the height dimension H1 of the rib 50 described above.

This makes it possible to prevent damage to the molded product when the housing 1 is made smaller to accommodate a low blood flow rate, and the air side case 3 is injection molded and then pressed with an ejector pin to release it from the mold. In other words, for a housing with a large capacity, the allowable deformation amount that can be tolerated in response to pressure from the ejector pin is large, but for a housing with a small capacity, the allowable deformation amount is small, so there is concern that the housing may be damaged by being pressed by the ejector pin during release. In contrast, the above-mentioned configuration improves strength with the protrusion 60 that receives the ejector pin, preventing damage during release.

In particular, by making the height dimension H2 of the convex portion 60 equal to or less than the height dimension H1 of the rib 50, when the flexible membrane 4 bends toward the air side chamber 13, the flexible membrane 4 will not come into contact with the end face 61 of the convex portion 60 before the rib 50. Therefore, it is possible to prevent the volume of the blood side chamber 12 from being reduced by the convex portion 60 limiting the amount of bending of the flexible membrane 4.

Furthermore, the end face 61 of the convex portion 60 is also concave so as to match the inner surface 32 of the air side case 3, which prevents the inward protrusion dimension of the end face 61 of the convex portion 60 from increasing partially. This prevents the volume of the blood side chamber 12 from decreasing. Also, by arranging the convex portions 60 symmetrically as described above, the stress caused by the pressure from the ejector pin can be distributed in a balanced manner throughout the air side case 3, achieving good demolding properties.

The above-mentioned protrusion 60 is not limited to being provided on the air side case 3, but may also be provided on the inner surface 22 of the blood side case 2. In this case, too, it is possible to obtain the effect of preventing damage during demolding after injection molding when the housing 1 is made compact. Furthermore, the object on which the above-mentioned protrusion 60 is provided is not limited to the egg-shaped pressure measurement chamber 100 exemplified in this embodiment, but can also be applied to other pressure measurement chambers having a spherical or flat housing.

The present invention can be suitably applied to a mixing chamber provided in a blood circuit for hemodialysis.

Reference Signs List 1 Housing 2 Blood side case 3 Air side case 4 Flexible membrane 5 Inlet port 6 Outlet port 11 Chamber space 12 Blood side chamber 13 Air side chamber 50 Rib 60 Convex portion 61 End surface 100 Pressure measurement chamber

Claims (5)

The blood supply device comprises a housing having a chamber space partitioned by a flexible membrane into a blood side chamber and an air side chamber, an inflow port through which blood flows into the blood side chamber, and an outflow port through which blood flows out of the blood side chamber,
The chamber space is egg-shaped (or rugby ball-shaped) or spherical and has a volume of 3000 mm3 or less ^;
A pressure measurement chamber in which, when the maximum area of a cross section perpendicular to the blood flow direction in the space occupied by the blood side chamber within the chamber space is defined as a chamber space maximum area A, and the opening area of the inlet port is defined as an inlet port area B, the area ratio A/B is 26.0 or less and 6.0 or more. The pressure measurement chamber according to claim 1, wherein the area ratio A/B is 22.6 or less and 18.5 or more. The housing has a blood side case and an air side case, and the blood side case and the air side case are brought together to form the chamber space ;
2. The pressure measurement chamber according to claim 1 , wherein at least an inner surface of said air side case is provided with a protrusion for receiving an ejector pin when demolding in injection molding. The pressure measurement chamber according to claim 3, wherein a rib is provided on the inner surface of the air side case to form an air passage between the flexible membrane and the inner surface of the air side case, and the protruding dimension of the protruding portion is equal to or smaller than the protruding dimension of the rib. The pressure measurement chamber according to claim 3 or 4, wherein the inner surface of the air side case is concave, and the end surface of the protrusion is also concave.

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