Method for determining compliance of a cavity in an elastomeric medical product for leak testing - Patent Application 20070122997

Abstract

The present invention relates to a method for determining the cavity volume of an elastomeric medical product (e.g., a latex product) for non-destructive leak testing, and a device for carrying out said method.

Description

[Technical Field]

[0001] The present invention relates to a method for determining the compliance of a cavity in an elastomeric medical product (e.g., a latex product) for non-destructive leak testing, and a device for carrying out said method. [Background technology]

[0002] Rubber-elastic medical products (e.g., rubber gloves, balloon catheters, condoms, etc.) undergo many tests before they are released onto the market. Penetration and burst tests are also performed to detect homogeneity defects. To test rubber-elastic medical products, the product is usually filled with a gas or liquid. In particular, depending on the size of the cavity thus formed, the volume of fluid required (e.g., N2, CO2, water, saline) varies to expand the product and allow testing of manufacturing errors for leaks.

[0003] In the case of gaseous fluids (such as CO2), a pressure reducing valve is used to regulate the volumetric flow rate required to then be delivered to the medical product.

[0004] The situation is different when using liquid fluids (such as saline), where for example peristaltic pumps are used, which make it possible to vary the volumetric flow rate by controlling the pump rotation.

[0005] By introducing a volume flow into the cavity, the cavity fills with fluid and the pressure in the cavity increases, simultaneously causing the cavity of the medical product to expand.

[0006] The so-called equation C c =V c / p c Using the volume V c and the resulting pressure p c Using the relationship, the compliance (extensibility) of the cavity, C c can be determined as a static characteristic (see Figure 1a).

[0007] Compliance C c The reciprocal of is the elasticity E c =1 / C c It is considered to be.

[0008] Here, the basic condition is that this particular pressure in the cavity must not have any adverse effects on the medical product (except in this case a burst test intended to destroy the product). For this reason, a pressure sensor is usually used to determine the cavity pressure. By appropriate adjustment, the volumetric flow rate required to prevent a cavity pressure that would damage the product can be calculated. The required volumetric flow rate is therefore achieved by adjusting the pressure reducing valve or peristaltic pump. However, it must be taken into account that the pressure is not measured during the fluid supply. For the pressure measurement, the fluid supply is briefly interrupted to achieve pressure equilibrium. The pressure equilibrium value represents the actual pressure in the medical product. After the measurement, the venting continues.

[0009] Depending on the medical product and its size, a significant change in volume may be required to inflate the elastomeric product to the desired pressure (see Figure 1b).

[0010] Therefore, in practice, the user of the test device must perform many necessary settings to communicate information about the product and its size to the device. In connection with quality assurance measurements, a small number of products are often selected from a product batch and subjected to corresponding extended or burst tests on a separate test device. Manual input of individual product parameters (e.g., product type and size) can lead to errors. The same applies to small batch production.

[0011] From that information, in particular parameters and limits for controlling / adjusting the device can be derived, for example a data set quantifying the maximum allowable fluid flow rate is thus loaded.

[0012] When the product is larger than initially estimated, expansion of the product takes significantly longer, resulting in undesirable measurement delays. However, when the product is smaller than initially estimated, pressure may be achieved significantly faster, potentially resulting in product damage.

[0013] If a user sets a faulty product and / or an incorrect product size on the test device (e.g., by preselecting the wrong glove size (adult or child) or by selecting a balloon catheter instead of a glove), this can result in faulty behavior of the device.

[0014] To date, prior art devices and methods have been unable to solve the problems described. Relevant prior art documents include U.S. Patent Application Publication No. 2007 / 0083126, U.S. Patent Application Publication No. 2010 / 0236555, German Patent Application Publication No. 4309380, German Patent Application No. 19809867, and Tautorat, C. et al., "Balloon-based measuring systems for compliance investigations," Current Directions in Biomedical Engineering 4(1), 2018. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] US Patent Application Publication No. 2007 / 0083126 [Patent Document 2] US Patent Application Publication No. 2010 / 0236555 [Patent Document 3] German Patent Application Publication No. 4309380 [Patent Document 4] German Patent No. 19809867 [Non-patent literature]

[0016] [Non-Patent Document 1] Tautorat, C. et al., “Balloon-based measuring systems for compliance investigations” Current Directions in Biomedical Engineering 4(1), 2018 Summary of the Invention [Problem to be solved by the invention]

[0017] There is a need for a medical technology device adjustment system that automatically determines critical cavity characteristics. [Means for solving the problem]

[0018] The present invention discloses a technological device for introducing a fluid into an elastomeric medical product, which device automatically determines the characteristics of the cavity and thus the necessary operating parameters.

[0019] A fluid reservoir (1) from which a fluid is taken and supplied to a supply unit (4) using a connecting element (2). The fluid can be a gas (e.g., CO2 or N2) or a liquid (e.g., saline).

[0020] A regulating pump (actuator or supply unit (4)) for supplying fluid in a regulated manner.

[0021] A device for measuring the volumetric flow rate of a fluid (5).

[0022] A pressure sensor (6) for determining the dynamic and static pressure of the fluid.

[0023] A connecting element (7) (e.g., tubing) for delivering fluid from the device to a medical product (8).

[0024] An electronic storage element (not explicitly shown) serving to detect the measurement data, as well as an electronic computing unit (e.g., a microcontroller) for sending the necessary control commands to the actuators, evaluating the data, and loading / writing parameter data sets from / to the storage element. [Effects of the Invention]

[0025] With a medical-technical device including said component, the compliance of the cavity can be determined automatically using the volumetric flow rate and pressure values, in order to avoid operational errors by staff. To achieve this goal, different determination methods can be applied, which are explained below. [Brief explanation of the drawings]

[0026] [Figure 1a] FIG. 1a shows the relationship between the volume Vc of the body cavity and the resulting pressure pc. [Figure 1b] Figure 1b shows the relationship between the volume Vc of the large and small body cavities and the resulting pressure pc. [Figure 2] FIG. 2 shows a medico-technical device (3) for delivering fluids according to the invention, comprising the following components: [Figure 3] FIG. 3 shows the relationship between the cumulative flow rate q and time t and the relationship between the partial pressure p and time t. [Figure 4] Figure 4 shows a pV diagram that shows the relationship between partial pressure pc and volume Vc. [Figure 5] FIG. 5 shows the relationship between the cumulative flow rate q and time t and the relationship between the partial pressure p and time t. [Figure 6] FIG. 6 shows the relationship between the cumulative flow rate q and time t and the relationship between the partial pressure p and time t. [Figure 7] FIG. 7 shows the relationship between the cumulative flow rate q and time t and the relationship between the partial pressure p and time t. [Figure 8] FIG. 8 shows Vc / pc in a pV diagram. [Figure 9] FIG. 9 shows the relationship between the actual cavity pressure p and time t, and the relationship between n and time t. [Figure 10] FIG. 10 shows the relationship between the cumulative flow rate q and time t and the relationship between the partial pressure p and time t. [Figure 11] FIG. 11 shows Vc / pc in a pV diagram. DETAILED DESCRIPTION OF THE INVENTION

[0027] Method Ia First, a connecting element (fluid line) is used to connect the elastomeric medical product to the device. Then, the device is turned on. Before the first application of volumetric flow, the device determines the pressure in the cavity. Then, an actuator is used to generate a predetermined temporal volumetric flow q (e.g., a pulsed volumetric flow of a defined length of time). The volumetric flow causes a pressure increase q in the cavity. c occurs.

[0028] The measuring unit allows the volume V to be determined by integrating the volume flow rate. After defining the volume flow rate, the device stops the supply and determines the static pressure in the cavity. Therefore, the partial pressure increase (dp c / dV c ) can be used to determine the elasticity. This procedure can be repeated until the desired base pressure of the cavity is achieved. A so-called pV diagram can then be derived from the partial pressure increase. This diagram therefore provides information about the size of the cavity, i.e., the size of the medical product. A comparison of the system parameters then allows for the parameterization and selection of optimal system parameters (e.g., maximum flow parameters, control parameters, and regulation parameters). The automatic cavity detection can be confirmed by user confirmation of the option.

[0029] An example of this method is shown in Figure 4. Two volumes V1 and V2 are fed into a cavity with a time offset. Then, the pressure p c increases, and the pressure sensor p d can be used to determine the cavity pressure, which allows us to determine the operating point V c1 =V1, p c1 =pd1 , and V c2 =V2+V1, p c2 =p d2 Then, for example by linear approximation, an approximation of the pV diagram can be calculated (see Figure 4). The "transient response" of the pressure measurement signal at the start and stop of the volumetric flow can be clearly seen in the measurement diagrams (bottom diagrams of Figures 5 to 7).

[0030] Method Ib In practice, in product manufacturing, there are occasional cavity leaks. Due to this unknown amount of fluid leakage, such leaks will prove the procedure of Method Ia incorrect. To compensate for the effect of leaks on the measurement data, Method Ia is extended as follows:

[0031] Pressure is generated in the cavity by a pressure regulating device. In this case, the volumetric flow rate required to achieve the desired pressure is predefined. In a closed cavity with no leaks, the pressure regulating device adjusts the volumetric flow rate to zero when the desired pressure is achieved (see Figure 6).

[0032] If the medical product has an existing leak, the pressure regulation system will permanently adjust the volumetric flow rate to compensate for the leak. This volumetric flow rate required to maintain pressure is the leakage volumetric flow rate q at the existing cavity pressure. l This is shown exemplarily in Figure 7. The leakage volume flow rate q l From this, the volumes V2 and V3 leaving the medical product due to leakage can be determined. The introduced volume can then be determined from the leakage rate.

[0033] Cavity p when volume flow stops c1 is the pressure drop across the connecting element and the measured pressure p d1 can be determined or approximated by prior knowledge of p d ≒p c1 is.

[0034] Here, the evaluation can be applied as in method Ia. The reference pressure can be (temporarily) increased to allow for several operating points for the calculation of the pV diagram.

[0035] By iteratively testing other reference pressure values, different operating points on the pV diagram and therefore cavity sizes can be determined.

[0036] Method II The actual operating point of the pV diagram of the medical product can be determined during device operation. c =ΔV c / Δp c ) indicates a large product, or a large value indicates a small product. To obtain this information, a measurement pause occurs during the operation of the device. Here, the volumetric flow rate is briefly interrupted and the static cavity pressure p c1 is determined. The actuator is then used to generate a predetermined temporal volumetric flow rate (e.g., a pulsed volumetric flow rate of a defined length of time). The volumetric flow rate generates a pressure increase in the cavity. By integrating the volumetric flow rate, a measuring unit can determine the volume V2 delivered during this period. After defining the volumetric flow rate, the device stops the delivery and the static pressure p in the cavity is increased. c2 The device then resumes normal function (see Figure 7). From the measurement, ΔC c =V2 / (p c2 -p c1 ) Unlike Method I, complete information about the cavity size or pV diagram is not known. Therefore, only this information is applied to the actual operating point of the volumetric flow rate required to maintain the cavity pressure. However, at this operating point, the appropriate settings and the actually determined characteristic values ​​can be adjusted relative to the default settings selected by the user (see Figure 8). Therefore, if there are discrepancies, the device can automatically adjust the device's parameter set to allow the user to perform an intervention and optimize the system setup.

[0037] The method is particularly suitable for testing balloon catheters. Depending on the application, the balloon catheter may contain openings, which represent the amount of leakage. The presented method allows the compliance C c (C c =V c / p c ) measurements can be performed. In addition, burst tests (or tear tests) can be performed.

[0038] Method III During device operation, the pressure temporarily increases. To achieve this goal, active pressure control / regulation is used. The additional volume required to obtain the desired cavity pressure is determined during the pressure increase phase. From the additional volume, the partial volume value (ΔC = ΔV / Δp) can be determined. This is identical to the procedure in Method II. However, Method III can also be used during the initial cavity filling phase. To achieve this goal, the desired reference pressure for pressure regulation is increased in a quasi-steady state (very slowly over time or in stages). Pausing the measurement does not require current system parameters for the device and the connection unit between the device and the medical product. Therefore, the volume and generated pressure data can be transferred to a pV diagram. This provides a basis for deriving the cavity size or product type, similar to Method I. Therefore, it offers the possibility of parameterizing and selecting optimal system parameters (e.g., maximum flow parameters, control parameters, and regulation parameters). Automatic cavity detection can be confirmed by user confirmation of the option.

[0039] Method IV In Method II, the actual cavity pressure p c1 After determining the volumetric flow rate, the pressure rise at the sensor correlates with the pressure rise in the cavity (see Figure 9). Therefore, the resulting cavity pressure p c2 There is no need to measure the increase Δp c(See Figure 10.) After the value is determined, the device resumes its previous operation.

[0040] Therefore, in contrast to Method II, in Method IV, the cavity pressure p c2 Although exact knowledge of the value of is lacking, the same fractional increase occurs, and thus the value can be used by the user to compare the device parameter set with the determined cavity value (Figure 11) and correct it, if necessary, to ensure optimal parameterization of the device. [Explanation of symbols]

[0041] (1) Fluid reservoir (2) Fluid connection (a fluid supply tube between the reservoir and the medical-technical device (3) for supplying the fluid) (3) Medical technology devices for delivering fluids (4) Supply device (5) A device for measuring the volumetric flow rate of a fluid (6) Pressure sensor (7) Fluid connection (8) Rubber elastic medical products

Claims

1. Compliance C of a cavity of a leaky elastomeric medical product using a medical technology device ｃ 1. A method for determining a) controlling the introduction of fluid into said cavity; b) determining the leakage volumetric flow rate, which is the volumetric flow rate of said fluid required to maintain the pressure in said cavity at a predetermined pressure; c) setting a target pressure for the cavity; d) controlling the introduction of said fluid into said cavity at an additional volumetric flow rate greater than said leakage volumetric flow rate; e) controlling the pressure of the cavity to increase from the predetermined pressure to the target pressure in a quasi-steady state; f) determining the additional volume (ΔV c ) from the start of step e) until the pressure in the cavity reaches the target pressure; g) Determination of the compliance C c (C c =ΔV c / Δp c ); and where: ΔV c is the time integral value of {(the additional volume flow rate)−(the leakage volume flow rate)} in step e), Δp c =(the target pressure)-(the predetermined pressure), That's the method.

2. Compliance C of a cavity in a leaky rubber elastic medical product ｃ A medical-technical device for determining at least one fluid reservoir (1), from which fluid is taken and supplied to a supply unit (4) through a connecting element (2); at least one metering pump (actuator) for supplying said fluid in a metered manner; at least one measuring device (5) for the volumetric flow rate of said fluid; at least one pressure sensor (6) for determining the dynamic and static pressure of said fluid; at least one connecting element (7) for supplying said fluid from said medico-technical device to the cavity (8); at least one electronic computing unit for providing the necessary control commands to said actuators; The electronic computing unit comprises the steps of: a) controlling the introduction of said fluid into said cavity; b) determining the leakage volumetric flow rate, which is the volumetric flow rate of said fluid required to maintain the pressure in said cavity at a predetermined pressure; c) setting a target pressure for the cavity; d) controlling the introduction of said fluid into said cavity at an additional volumetric flow rate greater than said leakage volumetric flow rate; e) controlling the pressure of the cavity to increase from the predetermined pressure to the target pressure in a quasi-steady state; f) determining the additional volume (ΔV c ) from the start of step e) until the pressure in the cavity reaches the target pressure; g) Determination of the compliance C c (C c =ΔV c / Δp c ); is configured to run where: ΔV c is the time integral value of {(the additional volume flow rate)−(the leakage volume flow rate)} in step e), Δp c =(the target pressure)-(the predetermined pressure), , a medical technology device.

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