METHOD FOR OPERATING AN ACTUATOR IN A MEDICAL APPARATUS, AND DEVICE THEREFOR

Abstract

The invention relates to a method for operating an actuator (22) in a medical apparatus (20), the actuator (22) being connected to a tube system. The medical apparatus (20) comprises: a control apparatus (28) having a pressure controller (35) for controlling a gas pressure; and a computing system (30). The method comprises the following steps: providing a nasal cannula at the tube system; defining a nasal gas end pressure at the pressure controller (35); controlling a nasal gas pressure at the actuator (22) by means of the pressure controller (35), in particular toward the nasal gas end pressure; discharging a conditioned gas from the actuator (22) to the tube system. The invention further relates to a device for operating the actuator (22).

Claims

1. A method for operating an actuator (22; 122) in a medical apparatus (20; 120), wherein the actuator (22; 122) is connected to a tubing system (17), and the medical apparatus has a control device (28; 128) with a pressure controller (35; 135) for controlling a gas pressure, as well as a computer system (30), wherein the method comprises the following steps: a) providing the tubing system (17) with a nasal cannula (16); b) specifying a final nasal gas pressure (P.sub.nSet) in the pressure controller (35; 135); c) adjusting a nasal gas pressure (P.sub.nasal) at the actuator (22; 122) with the aid of the pressure controller (35; 135), in particular towards the final nasal gas pressure (P.sub.nSet); d) delivering a conditioned gas from the actuator (22; 122) into the tubing system (17).

2. The method as claimed in claim 1, characterized in that the pressure control (35; 135) is carried out on the basis of at least one measured nasal pressure value (P.sub.mes) or on the basis of at least one pressure approximation (P.sub.n), wherein in particular, a variation in a nasal gas flow (F.sub.nasal) in the tubing system (17) occurs, which preferably occurs before setting the final nasal gas pressure (P.sub.nSet) at the pressure controller (35; 135) (step b)).

3. The method as claimed in claim 2, characterized in that the at least one pressure approximation (P.sub.n) is calculated on the basis of at least one internal measured pressure value (P.sub.int) and on the basis of at least one differential pressure approximation (dP.sub.sch) in the tubing system (17).

4. The method as claimed in claim 3, characterized in that the at least one differential pressure approximation (dP.sub.sch) in the tubing system (17) is calculated on the basis of an internal gas flow (F.sub.int), wherein the at least one differential pressure approximation (dP.sub.sch) is in particular calculated with the aid of a mathematical function, or preferably, is called up from a table (33) in the computer system (30), or more particularly calculated with the aid of at least one measured nasal pressure value (P.sub.mes).

5. The method as claimed in one of claims 1 to 4, characterized in that a minimum gas flow (F.sub.min) is determined or controlled through the tubing system (17), wherein the minimum gas flow (F.sub.min) is calculated in the computer system (30) using: $F_{\min }=\frac{V_d}{k*T_e}$ wherein V.sub.d is the dead space which in particular is calculated with the aid of an ideal body weight of a patient and a Radford constant, and k is a factor between 0.05 and 2, preferably 0.33, and T.sub.e is an expiration time.

6. The method as claimed in one of claims 1 to 5, characterized in that a maximum mean gas flow (F.sub.max) is provided through the tubing system (17), wherein the mean, maximum gas flow (F.sub.max) is preferably set to a value between 10 and 200 litres per minute, preferably to a value of 100 litres per minute.

7. The method as claimed in one of claims 1 to 6, characterized in that the nasal gas flow (F.sub.nasal) is controlled, wherein the nasal gas flow (F.sub.nasal) is preferably controlled as the inner cascade of the nasal gas pressure (P.sub.nasal).

8. The method as claimed in one of claims 1 to 7, characterized in that setting the final nasal gas pressure (P.sub.nSet) (step b)) is carried out automatically, wherein in particular, this is adjusted on the basis of a measured blood gas value, preferably a carbon dioxide value or an oxygen saturation value or a minimum gas flow (F.sub.min).

9. A device for carrying out a nasal flow therapy application, comprising an actuator (22; 122), a tubing system connection (23) for connecting a tubing system (17) to the actuator (22; 122) as well as at least one transducer (39), which provides measuring signals from at least one pressure measuring sensor (38), characterized in that a control device (28; 128) with a pressure controller (35; 135) is provided for controlling a nasal gas pressure (P.sub.nasal).

10. The device as claimed in claim 9, characterized in that a computer system (30) is provided, wherein the actuator (22; 122) is connected to the computer system (30) and the computer system (30) preferably has a storage unit (32), and the computer system (30) is configured in order to calculate at least one pressure approximation (P.sub.n) on the basis of at least one internal measured pressure value (P.sub.int) and on the basis of at least one differential pressure approximation (dP.sub.sch) in the tubing system (17), and preferably the pressure controller (35; 135) is configured to control the nasal gas pressure (P.sub.nasal) pertaining to the tubing system (17) on the basis of the at least one pressure approximation (P.sub.n).

11. The device as claimed in claim 9 or claim 10, characterized in that a pressure measuring device (160) is provided for detecting at least one measured nasal pressure value (P.sub.mes), wherein the pressure controller (35; 135) controls the nasal gas pressure (P.sub.nasal) pertaining to the tubing system (17) on the basis of the at least one measured nasal pressure value (P.sub.mes), and preferably a flow measuring sensor (41) is provided for measuring an internal gas flow (F.sub.int) in the medical apparatus (20; 120).

12. The device as claimed in one of claims 9 to 11, characterized in that a humidifier (19) is provided, wherein in particular, the humidifier (19) is disposed on the tubing system (17), and/or a temperature control system is provided for controlling the temperature of the conditioned gas.

13. The device as claimed in one of claims 9 to 12, characterized in that a flow controller (40; 140) is provided for controlling a nasal gas flow (F.sub.nasal), and in particular a cascaded control structure (36; 136) is provided, wherein the pressure controller (35; 135) forms an outer cascade for controlling the nasal gas pressure (P.sub.nasal) and a flow controller (40; 140) forms an inner cascade for controlling the nasal gas flow (F.sub.nasal).

14. The device as claimed in one of claims 9 to 13, characterized in that an oxygen dosing device is provided, and preferably an input and output device (45; 145) is provided, wherein in particular, the input and output device (45; 145) has a display unit (46) and is preferably a touch screen (47).

15. The device as claimed in one of claims 9 to 14, characterized in that a measuring device is provided for measuring blood gas, preferably for measuring carbon dioxide and/or for measuring oxygen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] In the figures:

[0083] FIG. 1 shows a system for carrying out a nasal flow therapy application,

[0084] FIG. 2 shows a first embodiment of a device in accordance with the invention for carrying out a nasal flow therapy application,

[0085] FIG. 3 shows a further embodiment of a device in accordance with the invention for carrying out a nasal flow therapy application,

[0086] FIG. 4 shows a flow diagram for a first embodiment of the method in accordance with the invention, without a pressure measuring device, and

[0087] FIG. 5 shows a flow diagram for a further embodiment of the method in accordance with the invention, with a pressure measuring device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0088] FIG. 1 shows a system 15 for carrying out nasal flow therapy on a patient. The system 15 comprises a tubing system 17 and a medical apparatus 20 with an actuator 22. The tubing system 17 comprises a tube 18 and a nasal canula 16, and is connected to the actuator 22 of the medical apparatus 20. A humidifier 19 is disposed on the tubing 18. The actuator 22 makes conditioned gas available to the tubing system 17 or the nasal canula 16 and which is delivered to the environment or to a patient through the tubing system 17 or through the nasal canula 16. Depending on the composition of the gas, this could be a respiratory gas, for example, which is administered to a patient to support breathing.

[0089] FIG. 2 shows a first embodiment in accordance with the invention of the medical apparatus 20 from FIG. 1 and comprises a tubing system connection 23 for connecting up the tubing system 17. The actuator 22 in the medical apparatus 20 has a digital-to-analogue transducer 24 and is connected to the tubing system connection 23. In a non-limiting manner, the actuator 22 consists of a blower and/or an oxygen connection and a valve and in particular a humidifier (not shown).

[0090] The medical apparatus 20 has a control device 28 which contains a computer system 30, a storage unit 32 and a cascaded control structure 36. In the control device 28, the computer system 30, the storage unit 32 and the cascaded control structure 36 are connected together in order to exchange data. The storage unit 32 has a table 33 for storing gas pressure data and gas flow data. The control device 28 has a pressure controller 35 for controlling a nasal gas pressure P.sub.nasal, which is connected to the flow controller 40 in order to exchange data. The pressure controller 35 is configured such that the actuator 22 keeps the gas at a constant nasal gas pressure P.sub.nasal. The control device 28 has a flow controller 40 for controlling the nasal gas flow F.sub.nasal, which is electrically connected to the digital-to-analogue transducer 24 of the actuator 22. In this regard, the pressure controller 35 and the flow controller 40 are connected together by means of a cascaded control structure 36, wherein the pressure controller 35 forms an outer cascade and the flow controller 40 forms an inner cascade.

[0091] The medical apparatus 20 has an internal pressure measuring sensor 38 for measuring internal gas pressures P.sub.int which are specified or produced by the actuator 22. These are provided to the control device 28 as pressure measuring signals with the aid of an analogue-to-digital transducer 39.

[0092] The medical apparatus 20 has a flow measuring sensor 41 for measuring internal gas flows F.sub.int, which are specified or produced by the actuator 22. These are provided to the control device 28 as flow measuring signals with the aid of an analogue-to-digital transducer 42.

[0093] An input and output device 45 is disposed on the medical apparatus 20 and provides a display unit 46 with a touch screen 47 for inputting and displaying gas pressure values and/or gas flow values or gas pressure data and/or gas flow data. The input and output device 45 furthermore comprises a switch device 48 for selecting between an automatic pressure control and a constant pressure control. The input and output device 45 is connected to the control device 28 in order to exchange data.

[0094] The medical apparatus 20 has a terminal strip 49 for connecting measuring devices or dosing devices. The terminal strip 49 is connected to the control device 28. Non-limiting examples in this regard which may be connected are a measuring device for measuring blood gas such as a carbon dioxide measurement and/or an oxygen measurement, an oxygen dosing device with an oxygen connection and a valve (not shown).

[0095] The medical apparatus 120 shown in FIG. 3 substantially corresponds to the medical apparatus 20 as described in relation to FIG. 2. The medical device 120 differs therefrom in that a pressure measuring device 160 for detecting measured nasal pressure values P.sub.mes is provided and the medical apparatus 120 is preferably a ventilator. In this regard, the medical apparatus 120 has a control device 128 which has the components and their technical functions described in respect of FIG. 2. Furthermore, the medical device 120 has an input and output device 145 which has the components and their technical functions described in respect of FIG. 2.

[0096] The pressure measuring device 160 is connected to the terminal strip 149. The measured nasal pressure values P.sub.mes measured by the pressure measuring device 160 are transmitted to the control device 128 with the aid of the analogue-to-digital transducer 150. The measured nasal pressure values P.sub.mes are converted into control commands in the pressure controller 135 of the control device 128 in order to control the actuator 122. The control device 128 has a flow controller 140 for controlling the nasal gas flow F.sub.nasal, which is electrically connected to the digital-to-analogue transducer 124 of the actuator 122. In this regard, the pressure controller 135 and the flow controller 140 are connected together by means of a cascaded control structure 136, wherein the pressure controller 135 forms an outer cascade and the flow controller 140 forms an inner cascade. The control commands are transferred to the actuator 122 by means of the digital-to-analogue transducer 124.

[0097] FIG. 4 shows a first embodiment of the method in accordance with the invention for operating the actuator 22 described above in a medical apparatus 20 in accordance with FIG. 1 and FIG. 2. The tubing system connection 23 has already been connected to the tubing 18 of the tubing system 17 and the nasal canula 16 has been provided on or positioned on the tubing system 17 (step 70; step a)). Next, it is ensured that the nasal canula 16 has not been placed on a patient (step 71). Then follow several steps for calibrating the medical apparatus 20 together with the tubing system 17, wherein the internal gas flow F.sub.int of the gas is raised in a linear manner from 0 litres per minute to 100 litres per minute within a period of time of 10 seconds (step 72). During this period of time, the internal gas pressure values P.sub.int and the internal gas flow values F.sub.int are measured with the internal pressure measuring sensor 38 and the internal flow measuring sensor 41 and transferred to the control device 28. The respective differential pressure approximations dP.sub.sch are then calculated on the basis of the measured internal gas pressure or the measured internal gas pressure value P.sub.int and on the basis of the pressure approximation P.sub.n in the computer system 30, wherein:

P.sub.n=P.sub.int−dP.sub.sch,

and when P.sub.n=0, then dP.sub.sch=P.sub.int.

[0098] In this manner, the several internal gas measured pressure values P.sub.int correspond to the differential pressure approximations dP.sub.sch in the tubing system 17. These are stored in the table 33 of the storage unit 32 together with the measured internal gas flow values F.sub.int associated with them (step 73), whereupon the medical apparatus 20 has been calibrated for the tubing system connected to it.

[0099] Alternatively, the respective differential pressure approximations dP.sub.sch can be calibrated using mathematical functions, for example polynomial functions such as:

dP.sub.sch=R.sub.0+R.sub.1*F.sub.int+R.sub.1*F.sub.int.sup.2+ . . .

[0100] The constants R.sub.0, R.sub.1, . . . are then determined with the aid of a least square method. Further functions for determining the differential pressure approximation dP.sub.sch on the basis of the internal gas flow F.sub.int are linear functions or quadratic functions; this list is not exhaustive.

[0101] In a further step (step 74), the maximum, mean gas flow F.sub.max through the tubing system 17 is specified to be 100 litres per minute.

[0102] Next, an ideal body weight for a patient (IBW) (or the height and gender of the patient) and an oxygen concentration FiO.sub.2 in the medical apparatus 20 is set on the input and output device 45 and a measured, effective, internal, maximum gas flow F.sub.int, max and an expiration time T.sub.e are calculated in the computer system 30 (step 75).

[0103] Furthermore, the dead space V.sub.d is calculated with the aid of the ideal body weight (IBW) and a Radford constant, wherein the Radford constant is typically 2.2 mL/kg (V.sub.d=2.2 mL/kg×IBW) (step 76).

[0104] Next, the respective pressure approximation P.sub.n is determined with the aid of the measured internal gas pressure values P.sub.int and the differential pressure approximations dP.sub.sch stored in the table 33, whereupon the differential pressure approximation dP.sub.sch is determined with the aid of the measured internal gas flow F.sub.int (step 77).

[0105] Subsequently, a minimum gas flow F.sub.min through the tubing system is determined (step 78).

[0106] In this regard, the minimum gas flow F.sub.min is calculated in the computer system 30 using:

[00003]$F_{\min }=\frac{V_d}{k*T_e}$

[0107] wherein V.sub.d is the previously determined dead space, k is 0.33 and T.sub.e is the expiration time which has already been calculated.

[0108] In a further step (step 79), the medical apparatus 20 is interrogated as to whether the final nasal gas pressure P.sub.nSet is to be set automatically. The interrogation is made by the position of the switch device 48 on the medical apparatus 20 or by means of a specified setting in the control device 28.

[0109] In the case of non-automatic setting of the final nasal gas pressure P.sub.nSet, a set final nasal gas pressure P.sub.nSet is manually entered by the user with the input and output device 45 on the medical apparatus 20 (step 80; step b)).

[0110] Next, the final gas flow F.sub.nSet is determined as a function of the difference between the set final nasal gas pressure P.sub.nSet and the previously determined pressure approximations P.sub.n, so that the difference mentioned above tends towards 0 (zero adjustment), according to:

Calculate F.sub.nSet so that: P.sub.nSet−P.sub.n.fwdarw.0

[0111] whereupon the nasal gas pressure P.sub.nasal is adjusted towards the final nasal gas pressure P.sub.nSet (step 81; step c)). In this regard, the pressure control 35 is carried out first as the outer cascade of the cascaded control structure.

[0112] Furthermore, the upper limit of the final gas flow F.sub.nSet determined in step 81 is the previously determined maximum, mean gas flow F.sub.max and the lower limit is the previously determined minimum gas flow F.sub.min (step 82).

[0113] As an alternative to the steps mentioned immediately above (steps 80 to 82), in the case of an automatic determination of the final nasal gas pressure P.sub.nSet, a determination of a measured, effective, internal, minimum gas flow F.sub.int, min is carried out (step 83) as well as an interrogation as to whether the calculated minimum gas flow F.sub.min is smaller than the determined measured, effective, internal, minimum gas flow F.sub.int,min (step 84).

[0114] If the calculated minimum fragment F.sub.min is smaller than the determined measured, effective, internal, minimum gas flow F.sub.int,min, the control device 28 reduces the final nasal gas pressure P.sub.nSet and sets it (step 85; step b)).

[0115] If the calculated minimum fragment F.sub.min is greater than the determined measured, effective, internal, minimum gas flow F.sub.int,min, the control device 28 increases the final nasal gas pressure P.sub.nSet and sets it (step 86; step b)).

[0116] In both cases, the final nasal gas pressure P.sub.nSet is limited to a value between 0 mbar and 10 mbar (step 87).

[0117] Next, in step 88, the pressure control is carried out as the outer cascade of the cascaded control structure.

[0118] The upper limit of the final gas flow F.sub.nSet is the previously determined maximum, mean gas flow F.sub.max and the lower limit is the value zero (step 89).

[0119] Next, the measured, internal gas flow F.sub.int is adjusted towards the calculated final gas flow F.sub.nSet with the aid of the flow controller 40 and subsequently with the aid of the actuator 22 (step 90). In other words, a zero adjustment is carried out, in accordance with

F.sub.nSet−F.sub.int.fwdarw.0

[0120] so that the nasal gas flow F.sub.nasal is adjusted towards the calculated final gas flow F.sub.nSet. In this manner, the flow control is carried out as the inner cascade of the cascaded control structure.

[0121] Next, the control device 28 generates a suitable control command for the actuator 22 on the basis of step 90 and transfers it to the actuator 22, so that the actuator 22 delivers the conditioned gas into the tubing system (step 91; step d)).

[0122] Subsequently, steps 75 to 82 and step 89 to step 91 can be carried out several times.

[0123] As an alternative to this, the steps 75 to 79 and the steps 83 to 91 may be carried out several times.

[0124] FIG. 5 shows a further embodiment of the method in accordance with the invention for operating the actuator 122 described above in a medical apparatus 20 in accordance with FIG. 1 and in a medical apparatus 120 in accordance with FIG. 3, wherein the medical apparatus 120 comprises a pressure measuring device 160 or is connected to it, and which is configured to detect measured pressure values P.sub.mes.

[0125] In a first step (step 170), the maximum mean gas flow F.sub.max through the tubing system is set to 100 litres per minute.

[0126] Next, an ideal body weight of a patient (IBW) (or the height and gender of the patient) and an oxygen concentration (FiO.sub.2) is designated in the medical apparatus 120, and a measured, effective, internal, maximum gas flow F.sub.int,max and an expiration time T.sub.e are calculated (step 171).

[0127] Furthermore, the dead space V.sub.d is calculated with the aid of the ideal body weight (IBW) and a Radford constant, wherein the Radford constant is typically 2.2 mL/kg (V.sub.d=2.2 mL/kg×IBW) (step 172).

[0128] Subsequently, a minimum gas flow F.sub.min through the tubing system is determined (step 173).

[0129] In this regard, the minimum gas flow F.sub.min is calculated in the computer system using:

[00004]$F_{\min }=\frac{V_d}{k*T_e}$

wherein V.sub.d is the previously determined dead space, k is 0.33 and T.sub.e is the expiration time which has already been calculated.

[0130] Next, a final nasal gas pressure P.sub.nSet is manually input into the medical apparatus 120 by the user using the input and output device 145 (step 174; b)).

[0131] Subsequently, the measured nasal pressure value (P.sub.mes) is measured with the pressure measuring device 160 and transferred to the pressure controller 135 of the control device 128 via the analogue-to-digital transducer 150 (step 175).

[0132] Next, the final gas flow F.sub.nSet is determined as a function of the difference between the set first final nasal gas pressure P.sub.nSet and the previously measured nasal pressure value P.sub.mes, so that the difference mentioned above tends towards 0 (zero adjustment), according to:

Calculate F.sub.nSet so that: P.sub.nSet−P.sub.mes.fwdarw.0

[0133] whereupon the nasal gas pressure P.sub.mes is adjusted towards the first final nasal gas pressure P.sub.nSet (step 176; step c)). In this regard, the pressure control is carried out first as the outer cascade of the cascaded control structure.

[0134] Furthermore, the upper limit for the final gas flow F.sub.nSet determined in step 176 is the previously determined maximum mean gas flow F.sub.max and the lower limit is the previously determined minimum gas flow F.sub.min (step 177).

[0135] Next, the measured, internal gas flow F.sub.int is adjusted towards the calculated final gas flow F.sub.nSet with the aid of the actuator 122 (step 178). In other words, a zero adjustment is carried out, in accordance with:

F.sub.nSet−F.sub.int.fwdarw.0

[0136] so that the nasal gas flow F.sub.nasal is adjusted towards the calculated final gas flow F.sub.nSet. In this manner, the flow control is carried out as the inner cascade of the cascaded control structure.

[0137] Next, the control device 128 generates a suitable control command for the actuator 122 on the basis of step 178 and transfers it to the actuator 122, so that the actuator 22 delivers the conditioned gas into the tubing system (step 179; step d)).

[0138] Subsequently, steps 170 to 179 can be carried out several times.

LIST OF REFERENCE NUMERALS

[0139] 15 system [0140] 16 nasal canula [0141] 17 tubing system [0142] 18 tubing [0143] 19 humidifier [0144] 20 medical apparatus [0145] 22 actuator [0146] 23 tubing system connection [0147] 24 digital-to-analogue transducer for 22 [0148] 28 control device [0149] 30 computer system [0150] 32 storage unit [0151] 33 table [0152] 35 pressure controller [0153] 36 cascaded control structure [0154] 38 internal pressure measuring sensor [0155] 39 analogue-to-digital transducer [0156] 40 flow controller [0157] 41 internal flow measuring sensor [0158] 42 analogue-to-digital transducer for 41 [0159] 45 input and output device [0160] 46 display unit [0161] 47 touch screen [0162] 48 switch device [0163] 49 terminal strip [0164] 120 medical apparatus [0165] 122 actuator [0166] 124 digital-to-analogue transducer for 122 [0167] 128 control device [0168] 135 pressure controller [0169] 136 cascaded control structure [0170] 145 input and output device [0171] 140 flow controller [0172] 149 terminal strip [0173] 150 analogue-to-digital transducer [0174] 160 pressure measuring device [0175] 70-91 steps of method [0176] 170-179 steps of method [0177] P.sub.nSet first final nasal gas pressure [0178] P.sub.nasal nasal gas pressure [0179] P.sub.mes measured pressure value [0180] P.sub.n pressure approximation [0181] dP.sub.sch first differential pressure approximation [0182] P.sub.int first internal measured pressure value [0183] F.sub.min minimum gas flow [0184] F.sub.nasal nasal gas flow [0185] F.sub.max maximum mean gas flow [0186] F.sub.int, max effective, internal, maximum gas flow [0187] F.sub.int internal gas flow [0188] F.sub.int, min minimum, internal gas flow [0189] F.sub.nSet final nasal gas pressure