DE102007003454A1 - Heater for heating e.g. breathing gas tube, has electrical connections respectively formed at ends of heating sections between heating wires, where resistance of one of connections is controllable, and other is controllable or not - Google Patents

Abstract

The heater has a control device (9), a leading heating wire (1) and a recoiling heating wire (2) together forming a device-close heating section and a device-far heating section, and a breathing tube including an inspiration tube (5) and an expiration tube (6). Temperature sensors (7, 8) are respectively located at ends of the heating sections. Electrical connections (10, 11) are respectively formed at the ends of the heating sections between the wires. The resistance of the connection (10) is controllable, where the resistance of the connection (11) is controllable or not controllable.

Description

The The invention relates to the ventilation technique, in particular the heating of breathing gas hoses.

at Mechanical ventilation is the patient to be ventilated by means of a breathing tube pneumatically connected to the ventilator. The complete breathing tube again consists of an inspiratory tube and an expiratory tube on the patient side using a so-called Y-piece pneumatically connected to each other.

Around to avoid dehydration of the airways, the respiratory gas is usually by means of of an active respiratory gas humidifier moistened between heating control and the beginning of the inspiratory tube is arranged.

If no precautions are taken, but condenses a part of the water vapor contained in the breathing gas in the breathing tube. This leads to water retention and to a reduction in the effective humidity of the patient supplied Respiratory gas.

Out For this reason, according to the prior art, at least the inspiratory tube, conveniently but also the expiratory tube electrically heated. Known are for this heating several variants:

• - by one each within the inspiratory and expiratory tubing extending heating wire loop
• - by Wrapping of inspiratory and expiratory tubing by means of a Heizdrahtwendel, wherein the Heizdrahtwendel the inspiratory tube and the Heizdrahtwendel the expiratory tube gerfernfern means be connected to an electric wire,

Together All variants, it is always one of the respirator or respiratory gas humidifier (hereinafter with control unit designated) in the direction of Y-piece afferent Heating wire and one of the Y-piece to the control unit leading back Heating wire gives. Both form together with the control unit one closed circuit.

The Regulation of the breathing gas temperature is carried out according to the prior art by means of one at the end of the breathing tube, preferably the inspiratory tube or on the Y-piece arranged temperature sensor, via a temperature control circuit the heating power regulates.

at the ventilation of infants the peculiarity is that these are used in incubators or warm beds which are normally above ambient temperature is.

The leads to, that the device is located within the incubator or heat bed remote Part of the breathing tube a lower heating power to be supplied must, than the outside of the incubator located near the device Part of the breathing tube. Otherwise, the breathing gas supplied to the patient would get too warm. In addition, that also required for the temperature control Temperature sensor located immediately in front of the incubator input must become. Befände he would be inside the incubator due to the high incubator internal temperature of the Turn off the heating control loop and condensation would occur again of water vapor in the breathing tube.

Around all possible applications to be able to cover The heating of the breathing tube must consist of two independently exist existing heating sections, of which the device is outside of the incubator (first heating section) and the other devices within of the incubator (second heating section). You can because of opposite cool the incubator Ambient temperature assume that the first heating a greater heat output has to raise as the second heating section and that there is the case where the first heating section is switched on, the second heating section however, it is off. This requires one of the second heating section independent Control of the first heating section.

in the Case of the variant of an internal Heizdrahtschleife would have a short and a long heating wire loop are provided, the short one for the First heating section, the long heating loop for the first and the second Heating section together. This execution has the disadvantage that the double heating loops require a higher contacting costs and that in addition the free flow cross section is reduced in the hose.

in the Trap of the variant of an outside applied heating coil would have the heating coil of the first heating section be made double after the first heating section in the heating coil for the second Go over heating section to be able to. All this is very expensive and technologically difficult to control.

task The invention is to provide a heater for a breathing tube create, with only one leading and one returning heating wire within each heating section an independent heating of the first Heating section of the second heating section allowed.

A inventive solution this Task is specified in claim 1.

The Essence of the invention is that the Hin heating wire at the end of First heating section through a first electrical connection and on End of the second heating section through a second electrical connection with the repatriate Heating wire is connected, the resistance of the first electrical Connection is controllable and the resistance of the second electrical Connection is controllable or not controllable.

If the resistance of the first electrical connection is low, the current flows from the controller via the afferent Heating wire until the end of the first heating section, from there over the First electrical connection and the return heating wire again until to the control unit back. there Only the first heating section is heated.

is However, the resistance of the first electrical connection high, the current flows over the entire afferent Heating wire, the second electrical connection and the return Heating wire back, which heats the entire breathing tube.

in the Contains case of controllability the corresponding first or second electrical connection a controllable Element which can be used as transistor, diode, fet, thermistor, relay, Temperature switch or another controllable known to the engineer Element executed can be.

• – Im Falle eines Transistors oder eines Relais durch ein weiteres externes elektrisches Ansteuersignal,
• – Im Falle einer Diode durch Änderung der Polarität der Heizspannung,
• – Durch einen temperatursensitiven Schalters, z. B. einen Temperatursensor, der vom Atemgas angeströmt wird und einen FET ansteuert, der die Erste oder Zweite elektrische Verbindung öffnet oder schließt.
• – Durch Einbeziehung von Speicherschaltungen und Sendung bestimmter sequentieller Signale von dem Steuergerät, die von den Ersten und Zweiten elektrischen Verbindungen ausgewertet werden und zu dem gewünschten Schaltzustand führen.

The activation can take place in different ways:

• - In the case of a transistor or a relay by another external electrical drive signal,
• In the case of a diode, by changing the polarity of the heating voltage,
• - By a temperature-sensitive switch, z. B. a temperature sensor, which is flowed by the breathing gas and a FET drives, which opens or closes the first or second electrical connection.
• - By including memory circuits and transmission of certain sequential signals from the controller, which are evaluated by the first and second electrical connections and lead to the desired switching state.

used you have a diode as the first electrical connection and a wire as a second electrical connection, one obtains a particularly simple one Solution. The control of the resistor is done by polarity switching the heating voltage, because depending on the polarity, the diode is conductive or blocked. If it is conductive, it will only be the first heating section heated, because the voltage drop over the diode is so low that by the second heating section no significant Electricity flows. If the heating voltage is reversed and the diode is locked, then both the first and the second heating section heated.

used you have a temperature-sensitive switch, z. B. a temperature sensor in conjunction with a MosFet as a circuit breaker in the way that achieved when reaching the setpoint temperature of the MosFet, so scored the same effect, while still receiving a temperature control. at When the setpoint temperature is reached, the MosFet switches off. this is a especially cheap Solution, if you have the same arrangement for both the first and the second used electrical connection. In this case, you get a temperature control both the first and the second heating sections directly in the breathing tube. there it does not matter if the temperature sensors in the inspiratory tube or in the expiratory tube. However, it is preferable Localization in the inspiratory tube. As a switch, all known semiconductor switch but also used contact switch become.

In same way is natural also a pulse width modulated control of the switch possible, the their effect allows a quasi-continuous control. It makes sense to use a time-staggered switch on the first and Second electrical connection.

Temperature-dependent contact switch are also counted among the temperature-sensitive switches. at this expression the invention as a temperature-sensitive switch is a constructive unit between temperature sensor and switch (eg, MosFet) which are electrically connected directly to each other. This case is not to be confused with external temperature sensors, their signals over extra lines the control unit Taxes.

A similar Result can be achieved by using temperature-dependent resistors a positive temperature coefficient (PTC) in the first electrical Connection or Secondary Electrical Connection or both together. If the setpoint temperature is reached, the PTC becomes high-impedance, switches off and thus interrupts the heating circuit.

A further embodiment of the invention provides that the first electrical connection in particular by a controllable semiconductor, for. B. a MosFet is formed, the control input (gate) is acted upon by a control signal coming from the heating control and thereby the control of the resistance of the first electrical Connection takes place. Although this solution requires a further control line, but avoids the need to switch the heating voltage. It is suitable for retrofitting existing humidification systems.

The Same can of course also happen with the second electrical connection whose resistance likewise by a further control line and admission changed with control signals can be. It is clear to the person skilled in the art that this solution is not limited to transistors, MosFets and other controllable semiconductors but also by means of Electromechanical relay can be realized.

Temperature sensors, which provide a signal to the heater controller are preferred near the first electrical connection and / or near the second position electrical connection.

Hinführender Heating wire and return heating wire can as extending within the breathing tube Heizdrahtschleife or in the form of a heating wire coil connected to the hose accomplished be. The heating wire coils must not on the outer surface of the Be inflated. You can also by extrusion be introduced within the hose wall. In practice However, the outside has applied heating wire coil enforced.

It is also a mixed solution possible, at the leader Heating wire extends within the breathing tube and the Returning heating wire is designed as Heizdrahtwendel and vice versa.

in the Trap of the inside extending heating wire loop needed one heating loop each and a first electrical connection for the inspiration hose and the expiratory tube. Both heating loops are at the entrance electrically connected in parallel. When using a diode as the first electrical Connection becomes this immediately at the end of the first heating section between the two wires arranged, contacted with both and then with a water and temperature resistant Encased sealant, so that both wires have only a small spherical extension exhibit. As at the end of the first heating section preferably in the inspiratory tube space for A first temperature sensor is to be provided by design measures avoid that the hot wire may be the temperature sensor touched and this leads to a faulty temperature measurement. This can z. B. happen that the heating wire near the place of Temperature sensor made thicker so that the local resistance near the temperature sensor reduces and thus the local heating power at this point is reduced. One more way possibly also in combination to increase the heating wire thickness in it, the heating wire loop in place of the first temperature sensor constructively with the breathing tube over a spacer so too connect that to the returning heating wire the maximum possible Distance from the first temperature sensor to be introduced. In this intermediate piece can also be equal to the first electrical connection z. B. in shape a diode with integrated.

One such intermediate piece can also be executed as a ring which contains a hole, in which the first temperature sensor can be inserted and the on its outer wall perpendicular to the bore has two contacts, which over the first electrical connection, z. B. a diode are connected together. The leader Heating wire is used with the first contact and the return heating wire is electrically connected to the second contact.

It But it can also be ensured by other constructive measures that the one inside the hose extending Heizdrahtschleife big enough Distance from the temperature sensor has.

The same measures can also at the end of the second heating section relative to one to be introduced Second temperature sensor to be made. In the simplest case However, the Heizdrahtschleife ends at a distance of a few centimeters before the second temperature sensor and the second electrical connection is in this case by the piece of heating wire. made that in the transition from leading Heating wire to the returning Heating wire is at the end of the loop.

in the Trap on the inspiratory tube and expiratory tube applied Heizdrahtwendeln extend this close to End of both hoses, the leader Heating wire z. B. by the heating wire coil of the inspiratory tube and the return heating wire are formed by the heating wire coil of the expiratory tube. At the end of the first heating section and at the end of the second heating section get both heating wires two contacts each.

The associated contacts of both heating coils are connected to each other at the end of the first heating section via the first electrical connection and at the end of the second heating section via the second electrical connection. In the simplest case, the first electrical connection will be through a diode and the second electrical Connection formed by a simple wire and the control of the resistance of the first electrical connection is done by reversing the heating voltage.

Also in the case of Heizdrahtwendeln must by constructive measures ensured be that no adulteration the measurement signal of the first temperature sensor at the end of the first Heating path takes place. A technologically simple solution exists in it, both the inspiratory tube and the expiratory tube each in two partial tubes with their own Heizdrahtwendeln split and this constructive over a To connect sleeve together. In this sleeve is additionally the Contacting housed over the two Heizdrahtwendeln the same tube connected and to which the one connection of the first electrical connection connected. additionally contains it's an opening for the introduction of the first temperature sensor. The first electrical connection is located either in one of these sockets or in the connection line between the two.

These Muff can also run like this be that it includes inspiratory tube and expiratory tube, wherein the two above-described contacts and the first or Second electrical connection including the temperature sensor are integrated.

The wire sizes the heating wires for the First and second heating sections can be different but preferably they should be the same. You reach in the latter Trap that the specific heating power when heating only the first heating sections higher and thus the heating time shorter is when heating the entire breathing tube.

The First and second electrical connection can be with the back and forth Heating wire and with the breathing hoses constructive and electric on diverse Be connected. You can either integrated in the sleeve, they can also be as firm integrated unit directly in the connecting line between the two Airbags are located.

A another possibility However, this is the first or second electrical connection or both solvable together, in particular to be pluggable. In this case contain inspiratory tube and expiratory tube at the end of the respective heating sections one contact each for the leader and returning Heating wire. The first and the second electrical connection are as a plug constructively designed so that they also have two Contain contacts with the contacts of both hoses z. B. be connected by plugging. In a particularly favorable Execution of the Invention, these connectors still contain the associated temperature sensors. This solution can for both electrical connections are chosen.

Of the Advantage of the invention is that with only two terminals for the Heizspannungsversorgung as well as only one leading and a returning one Heating wire nevertheless an independent Control of the heating sections of the breathing tube is possible and thus the condensation of water vapor in the breathing tube can be safely prevented The invention is intended below Hand of an embodiment be explained using a diode as a first electrical connection.

1 shows the breathing tube, consisting of inspiratory tube 5 and expiratory tube 6 on the Y-piece 13 pneumatically connected to each other. inspiration tube 5 contains the leading heating wire 1 and expiratory tube 6 the returning heating wire 2 in the form of externally applied Heizdrahtwendeln. Both hoses are divided in two and on the sleeve shown in dashed lines 12 both pneumatically and electrically interconnected.

The first inspiratory heating section 14 belongs to the first heating section 3 and the second inspiratory heating section 15 belongs to the second heating section 4 , About the contact 16 are the first inspiratory heating system 14 , the second inspiratory heating section 15 as well as the first connection of the first electrical connection 10 connected with each other. Close to the contact 16 is in the inspiratory tube 5 an opening for introducing a first temperature sensor 7 , Shortly after the end of the second inspiratory heating section 15 there is an opening for the introduction of the second temperature sensor 8th ,

The first expiratory heating line 17 belongs to the first heating section 3 and the second expiratory heating section 18 belongs to the second heating section 4 , About the contact 19 are the first expiratory heating line 17 , the second expiratory heating section 18 and the second terminal of the first electrical connection 10 connected with each other.

The first electrical connection 10 is formed by a diode. It is at positive voltage to connection 20 (related to connection 21 ) conductive.

The end of the second inspiratory heating section 15 is about the contact 22 with the second electrical connection 11 and these in turn via the contact 23 with the end of the second expiratory heating line 18 connected. The second electrical connection 11 is only formed by a wire strand.

The control unit 9 has two control inputs for the signals of the temperature sensors 7 and 8th and two heating voltage outputs connected to the terminals 20 and 21 are connected.

The mode of action is as follows:
When the temperature at the first temperature sensor 7 lower than the setpoint temperature, the controller generates 9 a heating voltage at connection 20 with positive polarity, the diode of the first electrical connection 10 is the leading and only the first inspiratory heating section 14 and the first expiratory heating section 17 heated. Because of the diode voltage of only 0.6 V is the second heating line 4 supplied electrical power negligible.

When the temperature at the first temperature sensor 7 exceeds the setpoint temperature, the controller generates 9 a heating voltage at connection 20 with negative polarity, the diode blocks and the circuit closes across both inspiratory heating sections 14 and 15 , the second electrical connection 11 and both expiratory heating sections 17 and 18 ,

Will now also the setpoint temperature at the second temperature sensor 8th reached, the control unit switches 9 completely off.

The Control algorithms for providing the heating voltage in terms of value and polarity are known in the art.

1

Hinführender heating wire

2

rear Leading heating wire

3

First heating section

4

Second heating section

5

inspiration tube

6

expiratory

7

first temperature sensor

8th

second temperature sensor

9

control unit

10

First electrical connection

11

Second electrical connection

12

sleeve

13

Y-piece

14

First inspiratory heating section

15

Second inspiratory heating section

16

contact

17

First expiratory heating section

18

Second expiratory heating section

19

contact

20

connection

21

connection

22

contact

23

contact

Claims (7)

Heating for a breathing tube consisting in particular of a heating wire ( 1 ) and a return heating wire ( 2 ), both of which have a device-like first heating section ( 3 ) as well as a device-distant second heating line ( 4 ), a breathing tube consisting of inspiratory tube ( 5 ) and expiratory tube ( 6 ), one at the end of the first heating section ( 3 ) preferably the inspiratory tube ( 5 ) located first temperature sensor ( 7 ) and one at the end of the second heating line ( 4 ) located second temperature sensor ( 8th ), furthermore a control device ( 9 ), characterized in that between the heating wire ( 1 ) and the return heating wire ( 2 ) at the end of the first heating section ( 3 ) a first electrical connection ( 10 ) and at the end of the second heating section ( 4 ) a second electrical connection ( 11 ), wherein the resistance of the first electrical connection ( 10 ) is controllable and the resistance of the second electrical connection ( 11 ) is controllable or not controllable. Heater for a breathing tube according to claim 1, characterized in that the first electrical connection ( 10 ) consists of a diode and the second electrical connection ( 11 ) of a wire, wherein the control of the resistance of the first electrical connection ( 10 ) by the polarity of the control unit ( 9 ) produced heating voltage. Heater for a breathing tube according to claim 1, characterized in that the control of the resistance of the first electrical connection ( 10 ) is effected by a temperature-sensitive switch which determines the respiratory gas temperature at the end of the first heating section ( 3 ) detected. Heater for a breathing tube according to claims 1 and 3, characterized in that the control of the resistance of the second electrical connection ( 11 ) is carried out by a temperature-sensitive switch which determines the breathing gas temperature at the end of the second heating section ( 4 ) detected. Heater for a breathing tube according to claim 1, characterized in that the control of the resistance of the first electrical connection ( 10 ) or the control of the resistance of the second electrical connection ( 11 ) or both together via additional externally supplied control lines. Heater for a breathing tube according to claims 1 to 5, characterized in that the first electrical connection ( 10 ) or the second electrical connection ( 11 ) or both are firmly connected to the breathing tubes together. Heater for a breathing tube according to claims 1 to 6, characterized in that the first electrical connection ( 10 ) or the second electrical connection ( 11 ) or both are releasably connected together to the breathing tubes.