ACCESS DEVICES FOR MEASURING TEMPERATURE OF A PATIENT
An access device such as a catheter, or introducer, or any combination of the above is provided. Within the access device is at least one lumen, channel or instrument that carries or itself is a thermally active mass, such as infusion fluids, control wires, etc. A temperature sensor such as a thermistor is secured to the access device in order to measure the temperature of a temperature medium, typically blood, in a patient. Various insulating lumens, insulating members and mounting and extrusion configurations are provided by the invention to insulate the temperature sensor thermally from the thermal mass, which might otherwise degrade the accuracy of the temperature measurement. The invention also provides an arrangement whereby the temperature sensor is connected to an external monitor for display of the patient's temperature.
The present application is a continuation of U.S. Pat. No. 6,383,144, filed Jan. 18, 2000, and scheduled to issue on May 7, 2002.
FIELD OF THE INVENTIONThis invention relates to methods and devices for measuring the body temperature of a patient in conjunction with the placement within the patient of an access device, for example, a catheter or introducer.
DESCRIPTION OF THE RELATED ARTThe needs to properly treat a patient and to gain as much information as possible about the physiological state of a patient are often at odds with the desire to reduce discomfort to the patient as much as possible. For example, there is frequently a need both to deliver various medications to a patient, and also to monitor the patient's body temperature. Accordingly, catheters are often inserted into the vasculature of a patient to allow delivery of various medications, hydrating fluids, etc., and to measure blood pressure. The patient's body temperature, however, is monitored with a separate device, which is inserted separately.
Conventional devices for measuring temperature include the well-known oral thermometer, rectal, axillary (armpit), and tympanic (ear) thermometers and probes, as well as Foley catheters (bladder temperature), and nasopharyngeal probes (esophagus) probes. Each of these devices suffers from one or more shortcomings. The first disadvantage is obvious to anyone who has ever been the patient: It is uncomfortable enough to have a catheter inserted into one's vein or artery without also having to have a separate device inserted into one's rectum, bladder, ear or nose, or down one's throat.
The second disadvantage has to do with accuracy—taking a patient's temperature by placing a thermometer under her armpit or in her mouth may cause the least discomfort to the patient, but the temperature value this provides is usually less accurate and much more dependent on placement than temperature measurements of blood in a major vessel.
One way to overcome these disadvantages is to include some form of temperature sensor within the inserted catheter itself. This allows for measurement of the blood temperature, which is in most cases much closer to the patient's actual body core temperature. The problem then arises that other elements of the catheter system may have thermal properties that themselves affect the temperature that the sensor senses. This problem arises in the context of thermodilution systems for measuring cardiac flow. U.S. Pat. No. 4,817,624 (Newbower, 4 Apr. 1989), U.S. Pat. No. 5,176,144 (Yoshikoshi, 5 Jan. 1993), and Published European Patent Application 0 357 334 B1 (Inventors: Williams, et al., 7 Mar. 1990) for example, describe such systems. As is well known, in such a thermodilution system, the temperature of the cardiac blood flow is modulated according to a predetermined pattern that is created by the injection of an indicator, which is usually either a series of boluses of a relatively colder fluid, or heat. The downstream response to the temperature modulation is sensed by a thermistor and is used to calculate and estimate blood flow.
In systems such as Newbower's, temperature modulation is accomplished by cooling the blood through precisely dosed boluses of a thermally well-controlled fluid colder than the blood. In Williams, modulated cooling of the blood is accomplished using a heat exchange mechanism that does not require actual injection of any bolus into the blood stream. In systems such as Yoshikoshi's the blood is instead heated locally using a heating element that is mounted near the far (distal) end of a cardiac catheter. As before, a thermistor senses the downstream response profile, whose characteristics are used to calculate cardiac flow.
Such thermodilution systems have certain clinical limitations, since they must deal with several problems specific to this application. First is the problem of retrograde flow: If the thermistor is located proximal to the heater or bolus injection port, then the heated/cooled blood will flow back over the catheter tip. The temperature of the catheter itself, which may contain various other lumens, injectates, control wires, etc. can then affect the temperature profile of the thermally modulated blood and degrade the flow calculations.
To overcome this effect, the injection is replaced by a continuous infusion of indicator in order to obtain a new steady-state baseline; however, this is an undesirable clinical limitation due to the volume-loading the patient. Even when the thermistor is located distal relative to the heater/bolus port, this problem may still arise.
These thermodilution system catheters normally have a distal infusion lumen that passes beneath the thermistor or temperature sensor and exits at the tip of the catheter. Since the flow in such an infusion lumen can severely degrade the accuracy of the temperature sensor measurements, the flow is limited to a maximum amount in order for the blood flow measurement to still be accurate. Of course, such a limitation on infusion lumen flow is also undesirable from the clinical perspective.
An analogous problem of insulation arises in other cardiac devices as well, such as the catheter-based cardiac ablation system described in U.S. Pat. No. 5,688,266 (Edwards, et al., 18 Nov. 1997). In Edwards' system, an ablation electrode is used to kill tissue locally using heat, and one or more temperature-sensing elements are used to sense the temperature of the tissue to be ablated and allow precise control of the ablation temperature and time. Isolation, provided primarily by physical separation, is thus required between the electrode and the temperature sensors; otherwise, the sensors will tend to give readings that are too high.
At least one factor limits the use of these known systems in general use for measuring a patient's body temperature: These systems are not arranged to measure the patient's actual, natural body temperature at all, but rather the temperature of blood or some body tissue whose temperature the system itself has deliberately altered.
There are other devices, such as central venous catheters (CVC), peripheral catheters, and other catheter-like instruments such as introducers. As their names imply, such catheters do not require placement into the heart and are consequently used more frequently in different areas of the hospital. Unlike cardiac catheters, which are often more than 100 cm long and require an introducer for insertion, these devices are seldom longer than about 20-30 cm and can be inserted by the Seldinger technique. A CVC, for example, is often placed in a patient's jugular vein and is used for various infusions, for monitoring blood pressure, etc., through a number of lumens within the device.
An instrument such as a CVC often includes several different lumens which may carry a range of fluids (such as medications and other infusions), as well as instruments such as pressure transducers. Each of these fluids and instruments may be at different temperatures, or may have varying thermal properties, or both. Any measurement of temperature using such a catheter would thus risk serious thermal contamination from other portions of the catheter.
There are at present no known devices such as a CVC, peripheral catheter, or introducer that incorporate an arrangement for measuring blood temperature accurately. Therefore, it would be advantageous to be able to accurately measure temperature in conjunction with such access devices as catheters and introducers while eliminating the need to insert a secondary device into the patient in order to measure temperature, as is the current practice. Such devices would also provide a more accurate and less time-consuming body temperature measurement than non- or less invasive devices. This invention provides such an arrangement.
It would also be advantageous to be able to connect a CVC or similar catheter to a standard patient monitor. Not only would this bring the obvious benefit that the patient's temperature could be viewed at a glance along with other monitored parameters, but it would also make the temperature values available for other processing as needed. Many patient monitors, however, use a signal standard that is compatible with large thermistors or temperature sensors and not compatible with the output of miniature temperature sensors used on pulmonary artery catheters. The use of miniature thermistors is desirable because it allows for catheter sizes to be relatively small. One could of course reprogram the monitors, but such a solution to the problem would be costly and complicated, and may not be possible or practical in existing monitors. This invention provides an arrangement that allows a catheter-based temperature sensor to be connected to existing monitors.
An additional issue is that many patients, as their condition improves, do not require continuous monitoring of temperature, and therefore, do not require a dedicated connection between the catheter(s) and the monitor. At present, the dedicated connections limit how many patients the system can monitor, and increases the number of cables and connectors needed. It would be advantageous to free the system to allow monitoring more that one patient. This would, for example, enable nurse or physician to have a quick look at the patient's temperature, possibly enter it into the patient's chart, and then move on to other tasks or patients. It would therefore be beneficial to have an arrangement that provides this flexibility and simplicity. This invention does this as well.
SUMMARY OF THE INVENTIONIn general, the invention provides an access device, such as a catheter, an introducer, or combination of catheters, introducers, probes and the like, that allows more accurate sensing of body temperature, for example, of a temperature medium such as blood, by insulating a temperature sensor from thermal contamination caused by a thermal mass, such as an infusion fluid or an instrument, introduced in portions of the access device. In the preferred embodiment of the invention the access device is a central venous device that includes a temperature sensor such as a thermistor, a thermocouple, etc.
The access device is insertable into the patient at a location of the temperature medium, and the access device includes at least one thermal mass other than the temperature medium. The access device supports the temperature sensor and includes at least one insulating structure insulating the temperature sensor from the thermal mass.
In certain embodiments of the invention, each thermal mass is located within a thermal lumen within the access device. The temperature sensor may be mounted externally to an outer surface of the access device, or within a sensor lumen of the access device. The insulating structure preferably extends between the temperature sensor and each thermal lumen.
The temperature sensor may also be mounted in or on a carrier. The insulating structure is then preferably formed as a barrier within the carrier and the carrier is held in one of the lumens of the access device with the barrier extending between the temperature sensor and the thermal lumen. The carrier may be removably insertable in the lumen of the access device.
In other embodiments of the invention, a pair of ports is formed in an outer wall of the access device and a flow channel is formed within the access device and extends between the pair of ports. The temperature medium, such as blood, then occupies the flow channel. The flow channel is located between the temperature sensor and the thermal lumen, or between the insulating structure and the thermal lumen, and thereby not only increases thermal contact between the temperature sensor and the temperature medium, but it also thermally isolates the temperature sensor further from the thermal lumen. The flow channel may thus itself form the insulating structure.
In another embodiment of the invention, the access device has an opening in an outer wall and the temperature sensor, when in a deployed position, extends into the opening. This increases thermal contact between the temperature sensor and the temperature medium and further insulates the temperature sensor from the thermal mass. If the temperature sensor is mounted on a carrier, then ends of the carrier may be secured within the access device. The carrier is then positioned between the temperature sensor and each thermal lumen, thereby forming the insulating structure.
The temperature sensor may alternatively be mounted within the carrier, which then protrudes as a loop out through the opening in the outer wall of the access device. The ends of the carrier are then preferably secured within the access device. In this embodiment, the insulating structure comprises a flow channel for the temperature medium, which is formed between the carrier and the access device at the position of the opening, and thus between the temperature sensor and the thermal mass. One advantage of this embodiment is that the temperature sensor is exposed substantially over its entire outer circumference to the temperature medium, via only the carrier.
Alternatively, the temperature sensor may be a right-angle thermistor mounted to extend out of the opening mainly perpendicular to a central axis of the access device.
In another embodiment of the invention, the temperature sensor is adhesively attached to the access device. The adhesive may be dissolvable at body temperature, so that the temperature sensor separates from contact with the access device when in position within the patient.
The access device may include a plurality of lumens, whereby the temperature sensor is mounted within a recess in an insulating member. The insulating member, together with the temperature sensor, are then mounted within one of the lumens of the access device so that the insulating member extends between the temperature sensor and the thermal lumen.
In another embodiment of the invention, the insulating structure includes an insulating material that is co-extruded with the access device and surrounds either at least a portion of each thermal lumen, or the temperature sensor itself.
In yet another embodiment of the invention, the access device has a lumen and a sensor port and the temperature sensor is mounted on a distal tip of a separate device, for example, a probe. The probe is insertable into the lumen of the access device so that the temperature sensor extends through the sensor port.
The insulating structure may also comprises a distal tip of the access device itself. The tip is then preferably formed from an insulating material as a separate member, and the temperature sensor is mounted within the distal tip. Alternatively, the distal tip of the access device may be provided with a lengthwise extending slit. The temperature sensor is then mounted on a first side of the distal tip and at least one thermal lumen carrying the thermal mass extends through a second side of the distal tip. The distal tip, in a deployed position, then separates along the slit, with the first and second sides of the tip being located on either side of the slit.
In another embodiment of the invention, the insulating structure is a lumen or a chamber in the access device that is expandable to increase the distance between the temperature sensor and the thermal mass.
The access device according to the invention is preferably included as a sensing member in a more general system for monitoring the body temperature of a patient. In this system, the access device is insertable into the patient and is connected to a temperature monitor that converts a sensor output signal of the access device into a patient temperature signal and for displaying the patient temperature signal. A connector is then provided to connect the temperature sensor with the temperature monitor.
The system according to the invention preferably further includes an adapter in the temperature monitor. The adapter converts the sensor output signal into a predetermined display format. The temperature monitor may also be provided with a display and a power supply, in which case the entire monitoring system may be implemented as a hand-held, self-contained unit that is portable between different patients.
The invention also encompasses a method for measuring the body temperature of the patient. The main steps of the method according to the invention involve supporting the temperature sensor on the access device; inserting the access device into a blood vessel; introducing at least one thermal mass into the access device; and insulating the temperature sensor from the thermal mass. In the preferred method according to the invention, the thermal mass is introduced via a thermal lumen located within the access device. One then mounts the temperature sensor in a sensor lumen within the access device and forms at least one thermally insulating structure between the temperature sensor and the thermal lumen. In some embodiments, to provide the thermally insulating structure, one may introduce a thermally insulating material into a lumen within the access device.
The invention also comprises a method for manufacturing the access device. In the preferred embodiment, this method comprises extruding the access device, forming a thermal lumen through which a thermal mass is introduced, forming a sensor lumen through which a temperature sensor is introduced, and forming an insulating structure separating the sensor lumen from the thermal mass. In manufacturing the access device, the temperature sensor may be mounted in the sensor lumen at a distal end of the access device. A signal wire is then drawn from the temperature sensor to an external patient monitor.
BRIEF DESCRIPTION OF THE DRAWINGS
In broadest terms, this invention provides an arrangement or a device in which a temperature sensor is used with an access device, preferably a vascular access device, for insertion into the body of a patient. This invention also provides various insulating structures that reduce thermal contamination of the temperature sensor from other portions of the interior of the access device. The temperature sensor is designed to sense some temperature medium within the patient's body, for example, blood.
One example of the preferred access device of this invention is a central venous catheter (CVC), but it could be some other instrument that also carries or includes fluids or other devices—cumulatively “thermal masses”—that could affect the temperature at the temperature sensor. Examples of other access devices include peripheral catheters, introducers, obturators, and probes. In fact, the term “access device” also contemplates any combination of these devices, such as a combination of one or more introducers, catheters and probes. For example, a catheter is often inserted within an introducer, and either or both could be arranged according to suitable embodiments of the invention to improve the accuracy of temperature measurements.
In the context of this invention, a thermal mass is any substance or structure carried within the access device that has or could have a temperature and heat capacity such that heat flow into or out of the mass could significantly affect the sensed temperature. Here, “significantly” means so much that the temperature measurement would not be acceptably accurate for clinical use.
As used in this invention an “insulating structure” is any structure that insulates the temperature sensor from a thermal mass. As is described and illustrated below, insulating structures used in the invention, include, but are not limited to, a device lumen or any portion of a device lumen, a channel, a gap, a chamber or just an area provided immediately surrounding the temperature sensor. An insulating structure may also include an insulating material, for example, a ceramic, or a separate device such as a probe that is inserted into or through the access device.
The examples of suitable access devices described below are preferably made of biocompatible polymer materials, since in most cases they will be inserted at least partially into a patient. Polyurethane is the most common material, since it meets all normal requirements for thermal and mechanical stability when in a patient; PVC and Teflon are also acceptable, as well as other conventional materials. The access devices for use with this invention may, moreover, be made of an anti-microbial material or may be covered with material or coating having anti-microbial or thromboresistant properties.
The temperature sensor used in this invention may be any conventional device. The most easily implemented sensor is a thermistor, which is small, widely available and relatively easy to calibrate. Other temperature sensors may, however, also be used. Alternatives include conventional thermocouples and fiber optic temperature sensors. The only requirement is that the sensor should predictably change a measurable physical property, such as its electrical resistance or optical spectrum, in response to changes in temperature, and this change should be detectable externally via an electrical or optical conductor in such a way that temperature can be converted to an electrical signal. These devices, and the way in which their signals are conditioned for further processing are well known.
In the following discussion of the various exemplifying embodiments of the invention, it is assumed merely by way of example that the access device is a CVC, that the temperature sensor is a thermistor, that the catheter is inserted into a body vessel, such as a vein, and that the temperature medium whose temperature is to be determined is blood. The invention will work just as well with other access devices and sensors, insertion points, and temperature media, as will be obvious to those skilled in the art.
A conductor (shown as the dashed line 125), which forms a signal wire, connects the thermistor electrically (or optically, depending on the type of temperature sensor used) with external conditioning, processing and display circuitry 150. In
Assume now that one or more of the lumens 220, 222, 224 carries some fluid (or contains some instrument) with a thermal mass and temperature that could affect the temperature measured by the thermistor 120. For example, an infusion fluid might be administered through the lumen 220. If the temperature of the fluid is above or below that of the patient's blood, then it could influence the temperature measurement because of the thermal conductivity of the catheter material between the thermistor and the fluid. An additional insulating structure, such as a lumen or gap 250 is therefore preferably extruded in the catheter so as to extend, for example, laterally between the thermistor and all the other lumens 220, 222, 224.
The insulating lumen (gap) 250 is preferably as wide and thick as possible to maximize the degree of thermal insulation of the thermistor, given the minimum permissible material thickness required to maintain stability of the catheter and lumen walls, as well as the maximum outer diameter of the device. The minimum distance between the thermistor lumen 210 and the outer surface of the catheter 100 is, however, preferably as small as possible to ensure the best thermal contact between the thermistor and the surrounding blood.
The insulating structure, such as the lumen or gap 250 of
In
The lumen(s) 250 also does not need to be shaped as a generally laterally extending slit, as shown in
In yet another variation of the insulating lumen 250 it—that is, the catheter material around and defining it—is made elastic enough that the lumen 250 is inflatable after the catheter is inserted into the patient. For example, the lumen 250 could be formed to have flexible webs. Once the catheter is inserted, any suitable pressurizing material, such as air, an inert gas, foam, or some other known thermal resistance material could be pumped into the lumen 250, causing its cross-sectional area to expand and increase the gap or distance between the thermistor and thermal masses. The embodiment facilitates easy insertion of the device by keeping its outer diameter small, since the insulating lumen or structure is expanded only after the device is in place.
The lumens 220, 222, 224 may be used for any conventional purpose. Any or all of them may, for example, carry fluids, or act as channels for guiding other instruments such probes, pressure transducers, etc. Of course, they need not all have the same function—one lumen might be carrying an infusion fluid while another is a channel for an instrument.
In the embodiment of the invention shown in
In the embodiment of the invention illustrated in
In the embodiments of the invention shown in both
In this embodiment a port is formed as a cut-away opening 605 in the outer wall of the catheter 100. The thermistor is then positioned so as to lie within the opening in the catheter and thus be exposed directly to the blood over most of its surface are, without any portion of the catheter in between. The thermistor's signal wire 125 is also shown in
The thermistor 120 and its carrier 600 may be inserted into an existing or dedicated lumen 610 in the catheter so that the carrier extends between the thermistor and other lumens 620, 622 or thermal noise sources in the catheter. Note that the opening 605 preferably extends into the lumen 610 to ensure maximum direct contact between the thermistor and the surrounding blood.
The thermistor and carrier 600 may be inserted into the catheter with the thermistor in position in the opening 605 before the catheter is placed within the patient. Alternatively, before insertion, and assuming the carrier is made of a sufficiently flexible material, the thermistor and the far, distal end of the carrier 600 could be allowed to stick out of the opening 605, preferably bent back along the catheter wall and pointing away from the direction of insertion. Once thermistor catheter is placed in the patient, the physician could then pull on the proximal end of the carrier until the thermistor is pulled into place in the opening 605. The distal end of the carrier can then be made short, extending only a short distance from the thermistor, so that only its proximal end would be within the catheter. The carrier, which may be tubular, then forms an insulating gap beneath the thermistor, similar to the gaps 250, 350 and 550 in previous embodiments described above.
In the embodiment of the invention shown in
This “deployment” action may also be arranged by providing the signal wire with an elbow joint made of a memory metal that is straight (extending in the direction of the catheter) during inserting but that is bent in the relaxed state—when the potting compound dissolves, the joint would relax and bend, thus moving the temperature sensor out from the catheter wall. If it is not practical to form this memory elbow joint in the sensor's signal wire itself, then a piece of memory metal could be attached to the wire where the elbow joint is needed. The sensor could then also be potted within an indentation such as in
As
Once the catheter is in place, the physician could then insert the thermistor, for example by pushing it in with a wire, and could then push the thermistor and loop of the member 800 out through the opening 805 to deploy the temperature sensor, that is, the thermistor. One way to do this would be to insert a separate instrument that has a bend on it into, for example, a lumen in which the member 800 lies (or simply the interior of the catheter). Twisting the instrument with the bend under the thermistor would then push it out through the opening 805. Alternatively, if the far distal end of the tubular member 800 is fixed in the catheter, and if the member 800 is not too flexible, then it would push out through the opening by the physician pushing the proximal end inward.
In
Several different embodiments of the invention are described above. Common to all of the embodiments, however, is that they implement the method according to the invention by which the body temperature of a patient is sensed by a temperature sensor supported by an access device. As used here, the term “supported” means that the temperature sensor may be mounted on or within the access device; it may be permanently affixed to or within the access device; or it may be removably connected to or inserted into the access device. The term also includes any arrangement, as described for example in reference to
The access device is inserted into a patient, for example, into a vein, and at least one thermal mass is introduced into the access device. The temperature sensor is insulated thermally from the thermal mass. A signal wire is led from the temperature sensor to an external patient temperature monitor.
The invention also encompasses the method of manufacturing the access device. In most of the embodiments described above, this manufacturing method involves extruding the access device with a plurality of lumens—one lumen through which a temperature sensor is introduced and a signal wire is led (a sensor lumen), and at least one other lumen for carrying or guiding the thermal mass. The manufacturing method also includes the step of forming an insulating structure that thermally separates the temperature sensor from the thermal mass. The temperature sensor may be permanently or removably mounted at a distal end of the sensor lumen. The temperature sensor may be also mounted in a separate carrier which is placed in the sensor lumen. The manufacturing method may include some other or additional steps according to the embodiments described above, as will be understood by those skilled in the art.
Refer once again to
Furthermore, in some cases, the temperature output signal may be compatible with input signals of existing patient monitors, but this is not always the case. As a simple example, amplification (scaling) and impedance matching (or impedance isolation) are often required to convert the output signal into a signal form and type that can be processed and displayed for the user.
According to the invention, the functional relationships a) between sensor temperature and the sensor output signal, on the one hand; and b) between output signal characteristics (such as impedance, amplitude range, and whether in the form of a voltage or current) are predetermined in any conventional manner (for example, through normal calibration or by accepting the manufacturer's calibration data). The signal conditioning necessary to implement the relationships is then implemented in the adapter 160. The conditioned signal is then applied to the monitor 170 for processing (if needed) and display.
In some cases, the only signal conditioning required is scaling. This can be done using a conventional resistive network, with the sensor output signal forming the input and the system output signal being taken from an appropriate point in the network. Conventional passive components may then be used to provide any necessary further conditioning such as impedance matching. This has the advantage of implementing the adapter 160 as a totally passive device. In other cases, conventional active components such as operational amplifiers with known resistive, capacitive and inductive feedback and feedforward elements may be used to implement the signal conversion.
In many cases, the relationship between sensor output and temperature may be too irregular to implement accurately using purely passive or analog components. In these cases, the adapter may be implemented by including in the adapter 160 a conventional analog-to-digital converter (ADC), a microprocessor, and a memory; note that a single conventional digital signal processor combines all these features in one component and may therefore in many applications be a suitable implementation. The relationship between the sensor output and temperature can then be implemented as a look-up table in memory, or as parameters of an approximating function. Using known methods, the microprocessor may then take as an input to the lookup table or approximating function the sensed and ADC-converted sensor output signal and generate the corresponding temperature signal, which, after any further conventional conditioning, is applied to the monitor 170.
In one embodiment of the invention that is particularly useful in a busy setting where only a quick and easy look at a patient's temperature is needed, the entire conditioning, processing and display circuitry 150 is included in a single hand-held unit. In this case, the power supply will typically be batteries and the monitor may be as simple as a conventional, low-power LCD display (along with conventional driving circuitry) showing temperature to, say, single decimal precision.
Using such a self-contained, handheld device, a nurse would connect the device to the temperature sensor by attaching the cable 190 to the connector 180, and the patient's temperature would then be displayed on the display 174 in a predetermined format. The connector 180 is preferably a conventional device such as a male/female plug pair that would allow the nurse to quickly connect and disconnect the device for readings from different patients. This would allow the nurse to take readings of many patients' temperatures quickly, with no need to wait for a conventional thermometer to stabilize, and with little discomfort to the patients themselves. Indeed, the nurse could take an already catheterized patient's temperature while he is asleep.
Assuming sufficiently powerful batteries, the self-contained embodiment of the system 150 could also include not only a memory, but also a simple input device such as a button connected to an internal electrical switch. Whenever the nurse presses the button, the instantaneous measured temperature is stored in the memory portion designated for a predetermined number of values for the patient. A time stamp of the measurement could also be generated using known techniques and stored along with each stored temperature measurement. By later recalling the stored values, for example by pressing the button according to some predetermined pattern, the nurse could then view the patient's recent temperature history. The software and hardware components needed to implement this one-button storage and recall system, even classified for several different patients, may be similar to those used, for example, in conventional electronic hand bearing compasses found on many well-equipped sailboats.
As an additional feature, the hand-held system could be provided with conventional circuitry enabling it to download its stored temperature information to another system such as a supervisory computer or patient monitor. The way in which such a feature is implemented is known. The way in which such temperature values, time-stamped or not, are stored for one or more patients and then recalled for viewing on a display is also well known.
Several different embodiments of the invention have been described above. It should be understood, however, that these are merely illustrative. The invention is not to be limited to the particular forms or methods disclosed; rather, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the following claims.
Claims
1-20. (canceled)
21. A device for measuring a temperature of a temperature medium of a patient, the device comprising:
- an access device insertable into the patient at a location of the temperature medium, the access device including an outer wall and at least one thermal mass other than the temperature medium, wherein the thermal mass is located within a thermal lumen defined in the access device;
- a carrier configured to extend through a carrier lumen of the access device; and
- a temperature sensor supported by the carrier;
- wherein a port is defined in the outer wall of the access device in direct communication with the carrier lumen and the carrier is configured to position the temperature sensor proximal to the port to allow direct contact of the temperature medium with the temperature sensor.
22. A device of claim 21, wherein the carrier is positioned between the temperature sensor and the thermal mass so as to insulate the temperature sensor from the thermal mass.
23. A device of claim 21, wherein the port is larger than the temperature sensor and the carrier is configured to position the temperature sensor subjacent and within the port, allowing the temperature sensor to be substantially surrounded by and in direct contact with the temperature medium.
24. A device of claim 21, wherein the temperature sensor is mounted to the carrier by a thermally stable adhesive.
25. A device of claim 21, wherein the a distal end of the carrier is configured to extend out of the opening.
26. A device of claim 25, wherein the distal end of the carrier is further configured to bend back along the outer wall and away from a direction of insertion.
27. A device of claim 21, wherein a signal wire extends from the temperature sensor and at least partially along the carrier.
28. A device of claim 21, wherein the carrier is configured to extend out of the port past the outer wall so as to position the temperature sensor in the temperature meeting.
29. A device of claim 28, wherein the carrier is biased to extend out of the port.
30. A device of claim 29, wherein the carrier is biased to form an elbow joint.
31. A device of claim 30, wherein a signal wire is connected to the sensor and is also configured to form the elbow joint.
32. A device of claim 31, further comprising an adhesive compound extending over the sensor so as to keep the carrier and signal wire straight until dissolved by contact with the temperature medium.
33. A device of claim 28, wherein the carrier is a short tubular member that contains the thermal sensor.
34. A device of claim 33, wherein the tubular member has ends anchored within the access device and a middle portion extending through the port.
35. A device of claim 34, wherein the tubular member forms a loop with respect to the access device.
36. A device of claim 35, wherein the tubular member is configured to extend straight within the carrier lumen during insertion of the access device within the patient.
37. A device of claim 27, wherein the signal wire includes a substantially right angle bend adjacent the temperature sensor.
38. A device of claim 21, wherein the carrier is a signal wire connected to the temperature sensor.
39. A device of claim 38, wherein the temperature sensor is supported within the port by an adhesive compound.
40. A method of measuring a temperature of a temperature medium of a patient, the method comprising:
- inserting an access device into the patient at a location of the temperature medium;
- positioning a carrier supporting a temperature sensor in a carrier lumen of the access device until the temperature sensor is proximal to a port defined in an outer wall of the access device; and
- directly contacting the temperature medium through the port with the temperature sensor and measuring the temperature of the temperature medium.
41. A device for measuring a temperature of a temperature medium of a patient, the device comprising:
- an access device insertable into the patient at a location of the temperature medium, the access device including an outer wall and at least one thermal mass other than the temperature medium wherein the thermal mass is located within a thermal lumen defined in the access device;
- a temperature sensor supported on the outer wall of the access device so as to directly contact the temperature medium; and
- a signal wire connected to the temperature sensor and extending through an opening in the outer wall, into the access device and away from the patient within the access device.
42. A device of claim 41, further comprising an adhesive compound securing the temperature sensor to the access device.
43. A device for measuring a temperature of a temperature medium of a patient, the device comprising:
- an access device insertable into the patient at a location of the temperature medium, the access device including at least one thermal mass other than the temperature medium wherein the thermal mass is located within a thermal lumen defined in the access device;
- a temperature sensor; and
- an tip affixed to a distal end of the access device for positioning within the temperature medium and including an opening extending therethrough into communication with the thermal lumen, wherein the tip is comprised of an insulative material and supports the temperature sensor.
44. A device of claim 43, wherein the tip includes a split extending between the opening and the temperature sensor.
45. A device of claim 44, wherein a portion of the tip supporting the temperature sensor is configured to separate along the split from another portion of the tip through which the opening extends.
Type: Application
Filed: May 2, 2007
Publication Date: Feb 21, 2008
Inventors: CHARLES MOONEY (Costa Mesa, CA), Mark Konno (Laguna Beach, CA)
Application Number: 11/743,302
International Classification: A61B 5/01 (20060101);