EP1335691B1 - Method for regulating the inner pressure of an anti-decubitus support - Google Patents

Abstract

The invention relates to a method for regulating the inner pressure of an anti-decubitus support for a sick-bed. Said support comprises at least one hollow chamber which is filled with a liquid, the inner pressure resulting therefrom in the at least one hollow chamber being regulated in accordance with the body size and the weight of a patient. The aim of the invention is to distribute the pressure produced by the body of the patient over the support as homogeneously as possible by optimising the regulation of the appropriate inner pressure of the support, in order to avoid peak pressures in problem areas and thus the formation of pressure sores. To this end, during a testing period for different test persons respectively, an optimum inner pressure of the support is determined specifically for the respective construction of the support; the values determined are defined in a table of values in correlation with the body-mass index of the patient; and the inner pressure of the support is regulated for the patient on the basis of the table of values.

Description

The present invention relates to a method for adjusting the internal pressure of an anti-decubitus pad for a hospital bed according to the preamble of claim 1.

Such requirements are used in nursing and geriatric care, especially in patients who remain bedridden for an extended period of time, to prevent the development of pressure ulcers due to prolonged delays (bedsores), or to assist healing in pre-existing pressure ulcers. So-called anti-decubitus mattresses are known as fluid, in particular air-filled single or multi-chamber systems. In addition to dynamic systems, which operate with varying pressures in different, usually alternately filled or relieved chambers to avoid excessive stress on problem areas by intermittent discharge, static systems are used whose fluid pressure in one or more chambers is kept constant.

In static systems, the aim is to distribute the contact pressure generated by the patient's body on the pad as evenly as possible in order to prevent peak pressures in problem areas, which can lead to the development of pressure ulcers. A crucial role here comes from the system generated and maintained internal pressure of the support. Due to the natural anatomy and the uneven weight distribution of the human body, it seems impossible to achieve the optimum of a completely uniform load of all support points of the patient on the support. However, the choice of the correct internal pressure of the fluid-filled support can lead to a possible optimization according to the circumstances. This means that the differences between the load pressures, and thus the peak pressures at problem areas, are lower at an optimum fill pressure than at higher or lower pressures.

In addition to the physical conditions of the edition itself, in particular their size, construction and materials used, the patient himself plays the crucial role. This applies to both static and dynamic systems. An existing overlay can be used for a variety of patients, but must be individually adjusted to the optimum inflation pressure for each patient to achieve the optimization described above. For this purpose, in known static and dynamic systems, the filling internal pressure is set by the specialist personnel in the hospital or nursing home according to their own experience and / or the information provided by the manufacturer. As is known, a direct correlation is hereby used between the weight of the patient and the internal pressure of the support to be selected. This means patients with less Body weight is stored on the pad with low inflation pressure, while the inflation pressure increases as the patient's weight increases.

From DE 69019567 T2 there is known a generic method for operating a patient support system in which a microprocessor is preprogrammed to calculate a reference pressure to assist the patient based on the size and weight of a patient. Here, the height is used to associate body zones (head, shoulder, pelvis, etc.) of the patient, more precisely, their proportion by weight of the total weight of the patient, corresponding segment areas of the edition. The internal pressure of the individual segments is calculated as a function of factors which are multiplied by the weight and the size of the patient and depend inter alia on the elevation angle of the segments. So this method is based on the idea that you can assign exact parts of total body weight to certain body regions.

In practice, it has been found that the known support systems have only limited suitability to reduce the risk of decubitus ulcers. In particular, they are by no means able to reliably prevent the development of pressure ulcers. Scientific, e.g. empirical studies on the optimization of such overlay systems were not available so far.

It is therefore the object of the invention to provide a method for adjusting the internal pressure of an anti-decubitus pad, which overcomes the problems described above, in particular an optimization by improving the selection of the appropriate internal pressure allows.

The stated object is achieved by the method specified in claim 1. An advantageous development of the invention results from the dependent claim.

An optimal setting of the internal pressure of an anti-decubitus pad would be achievable if it were determined for each patient on the experimental route as an individual value. Such an approach is practically unrealizable, since such attempts are very time consuming and costly. In addition, they can not be expected patients. Therefore, the experiments are carried out according to the invention with healthy people (subjects). Such an approach seems obvious at first. However, the problem is to generalize the optimal values established for the subjects so that they are also substantially optimal for patients, assuming that individuals are due to the complexity of their anatomy and the uneven distribution of weight in the human body of individuals Distinguish individuals. Surprisingly, it has been found that, for such a generalization, the so-called body mass index known in the other context (hereinafter abbreviated to BMI) is suitable, which is calculated as follows: $$\mathrm{Weight\; in\; kg}/{\left(\mathrm{Size\; in\; m}\right)}^2\mathrm{,}$$

It has been shown that, for people with the same BMI, the internal pressure of the anti-decubitus pad can be set to substantially the same for equally good results. This is surprising in that people with the same BMI usually different total weights, parts by weight of individual body zones and body sizes. Thus, a simple solution has been found to transfer the test results to the day-to-day business, namely the storage of patients to prevent bedsores. For this purpose, a value table is set up on the basis of the test results, in which the BMI is correlated with the filling pressure determined for this BMI. It is then only the BMI of a patient to determine and read from the table of values, the corresponding internal pressure and adjust. It goes without saying that for the purposes of the present invention, instead of a physical value table, their values can also be stored in a storage medium and processed accordingly by means of an algorithm.

When using an "electronic value table", it is useful in a further embodiment of the method according to the invention to automate this so far that only the weight and height of a patient must be entered, and then the optimum internal pressure of the anti-decubitus support self-adjusting.

With the method according to the invention, the greatest possible distribution of the contact pressures over the entire bearing surface of the human body is achieved. Surprisingly, it has also led to significantly lower filling pressures in comparison with known static and dynamic methods and systems.

Hereinafter, a preferred embodiment of the present invention will be described by way of example with reference to a static system.

A static air-filled anti-decubitus system comprises a support for a hospital bed, which consists of at least one air-filled, pressure-tight chamber. The material for the overlay is a compliant airtight material (e.g., PVC). As airtight in this case, a support whose surface is perforated by small openings and thus emits a small amount of air to the outside, the amount of air discharged is below the available amount of air and thus always the desired internal pressure of the system can be achieved. The support includes an opening for an air hose through which air can be forced into or discharged from the chamber. The inlet or outlet port is connected via an air hose to a control unit. The controller includes a pressure gauge for measuring system pressure and a pump for filling the chamber with compressed air. The control unit further includes a control device which makes it possible to keep the system internal pressure constant by means of periodic checks of the actual pressure and comparison with the target pressure by appropriately replenishing compressed air or discharging air.

The controller further includes an input device to which the operator may alternatively input either the desired internal pressure of the system or the BMI of the patient, or alternatively, menu-driven, the values for body size and body weight of the patient. The input device is connected to a calculation unit which contains storage means for storing the input data as well as the formulas and / or value tables required for the calculation. The calculation unit is with a control unit connected such that the control unit receives its desired pressure value from the calculation unit.

In operation, the operator is prompted to enter the required data at the input device. If a target system pressure is already known, this can be entered directly. If the BMI of the patient is already known, this can be entered. Based on the stored formula or the stored value table, the calculation unit then calculates the required setpoint pressure from the BMI, which is then passed on to the closed-loop control device.

oder aus einer im Speicher hinterlegten Wertetabelle den BMI des Patienten und dann aus diesem BMI - wie oben - den erforderlichen Soll-Druck für das Auflagesystem.Otherwise, the operator sequentially enters the body size and body weight data. The calculation unit determines from this by means of the formula $$\mathrm{Weight\; in\; kg}/{\left(\mathrm{Size\; in\; m}\right)}^2$$

or from a value table stored in the memory the BMI of the patient and then from this BMI - as above - the required target pressure for the overlay system.

The set pressure thus determined or set is made available to the control unit of the filling device, which uses the hose connected to the air chamber and optionally a drain valve to set the desired internal pressure and keeps it constant.

Input calculation and control unit may also be integrated in a single, microprocessor-controlled circuit.

The appropriate values for the filling pressure as a function of the BMI of the patient were determined in advance in a series of experiments. For this purpose, test persons with different BMI were placed on the support and the pressure distribution on the support was measured by means of sensors at different filling pressures. For each BMI, optimum pressure, i. the most even pressure distribution on the support, determined.

For a PVC edition, for example, of the size 1900mm x 910mm (unfilled, with a filled height of about 110mm), with a wall thickness of 0.25mm per foil, consisting of an upper and a lower chamber, from a central position are separated from PVC, but communicate with each other via recesses in the edge region of the middle layer, wherein the individual layers are spot welded together, resulting in a so-called honeycomb structure, the following table of values resulted: Body mass index of the patient Internal pressure of the control unit (in mm Hg) 16.0 - 23.9 15 24.0 - 28.9 16 29.0 - 30.9 17 31.0 - 32.9 18 33.0 - 34.9 19 35.0 - 38.9 20 39.0 - 43.9 21 44.0 - 48.9 22 > 49 23

It will be apparent to those skilled in the art that these values are valid only for the above-described scope. For overlays with other specifications, the table of values (or a formula) for setting the optimum inflation pressure is for every conceivable BMI using the test method described above.

The overlay can also be made from a multi-chamber system of e.g. 20 elongated chambers which extend transversely to the longitudinal axis of the patient exist. The chambers do not communicate with each other; between the cavities of the chambers so no exchange of air and thus no pressure compensation can take place. Each of the chambers is provided with its own opening for supplying or discharging compressed air. Each individual chamber is assigned a control unit which can maintain the pressure set for this chamber.

Again, the pressures to be selected for the chamber are based on the BMI of the patient, the appropriate values being determined by testing as described above. Here, value tables can be determined separately for each of the chambers. Then these value tables are all stored and serve as a whole to control the controllers for each of the chambers.

Alternatively, a basic value and for this purpose deviations of the pressures of the individual chambers relative to the basic value can be determined. For example, a suitable base value based on a BMI can be determined, wherein at the same time it can be established that increasing the pressure in individual chambers and / or lowering the pressure in individual chambers leads to a more uniform pressure distribution and thus to even more gentle positioning of the patient , In this case physiological aspects can also be included. So it may be favorable for the patient, from an optimally uniform Diverge pressure distribution, because not all body parts are equally resilient.

Controlled by the control units assigned to the chambers, each of the chambers can maintain an individually set pressure. It is also possible, control technology groups of chambers summarize, which then have identical internal pressures.

By individual adjustment of the pressure of individual chambers, the operator can also specifically address the patient's situation, for instance after localization of a decubitus ulcer, by inducing a special pressure relief at critical points.

Claims (2)

1. Method for setting the internal pressure of an anti-decubitus support for a hospital bed with at least one hollow chamber filled with fluid, the resulting internal pressure in the at least one hollow chamber being set as a function of the body size and weight of a patient and at a trial stage an optimum internal pressure of the support being determined in each case specifically for the respective structure of the support for different test persons, characterised in that the values determined are placed in a values table in correlation to the body mass index of the respective test person, in that the body mass index of the patient is determined and in that setting the internal pressure of the support for the patient is done using the values table.
2. Method according to claim 1, characterised in that the internal pressure of the support is automatically set after input of the weight and size of the patient.