CONFIGURABLE PHYSIOLOGICAL MEASUREMENT SYSTEM

Abstract

A physiological measurement system has a sensor, a processor, a communications link and information elements. The sensor is configured to transmit light having a plurality of wavelengths into a tissue site and to generate a sensor signal responsive to the transmitted light after tissue attenuation. The attenuated light can be used by the system to determine a plurality of physiological measurements. The processor is configured to operate on the sensor signal so as to derive at least one physiological parameter after which of the plurality of physiological measurements the system is configured to or capable of measuring.

Description

BACKGROUND OF THE INVENTION

Spectroscopy is a common technique for measuring the concentration of organic and some inorganic constituents of a solution. The theoretical basis of this technique is the Beer-Lambert law, which states that the concentration c_i of an absorbent in solution can be determined by the intensity of light transmitted through the solution, knowing the pathlength d_λ, the intensity of the incident light I_0,λ, and the extinction coefficient ε_i,λ at a particular wavelength λ. In generalized form, the Beer-Lambert law is expressed as:

$\begin{array}{cc}{I}_{\lambda }=I_{0,\lambda }{}^{-d_{\lambda }·{\mu }_{a,\lambda }}& \left(1\right)\\ {\mu }_{a,\lambda }=\sum _{i=1}^n{\varepsilon }_{i,\lambda }·c_i& \left(2\right)\end{array}$

where μ_a,λ is the bulk absorption coefficient and represents the probability of absorption per unit length. The minimum number of discrete wavelengths that are required to solve EQS. 1-2 are the number of significant absorbers that are present in the solution.

A practical application of this technique is pulse oximetry, which utilizes a noninvasive sensor to measure oxygen saturation (SpO₂) and pulse rate. In general, the sensor has light emitting diodes (LEDs) that transmit optical radiation of red and infrared wavelengths into a tissue site and a detector that responds to the intensity of the optical radiation after absorption (e.g., by transmission or transreflectance) by pulsatile arterial blood flowing within the tissue site. Based on this response, a processor determines measurements for SpO₂, pulse rate, and can output representative plethysmographic waveforms. Thus, “pulse oximetry” as used herein encompasses its broad ordinary meaning known to one of skill in the art, which includes at least those noninvasive procedures for measuring parameters of circulating blood through spectroscopy. Moreover, “plethysmograph” as used herein (commonly referred to as “photoplethysmograph”), encompasses its broad ordinary meaning known to one of skill in the art, which includes at least data representative of a change in the absorption of particular wavelengths of light as a function of the changes in body tissue resulting from pulsing blood. Pulse oximeters capable of reading through motion induced noise are available from Masimo Corporation (“Masimo”) of Irvine, Calif. Moreover, portable and other oximeters capable of reading through motion induced noise are disclosed in at least U.S. Pat. Nos. 6,770,028, 6,658,276, 6,157,850, 6,002,952 5,769,785, and 5,758,644, which are owned by Masimo and are incorporated by reference herein. Such reading through motion oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all types of monitoring scenarios.

SUMMARY OF THE INVENTION

A physiological measurement system has a sensor that transmits optical radiation at a multiplicity of wavelengths other than or including the red and infrared wavelengths utilized in pulse oximeters. The system also has a processor that determines the relative concentrations of blood constituents other than or in addition to HbO₂ and Hb, such as carboxyhemoglobin (HbCO), methemoglobin (MetHb), fractional oxygen saturation, total hemaglobin (Hbt) and blood glucose to name a few. Further, such a system may be combined with other physiological parameters such as noninvasive blood pressure (NIBP). There is a need to easily configure such a physiological measurement system from compatible components capable of measuring various physiological parameters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general block diagram of a configurable physiological measurement system;

FIG. 2 is a detailed block diagram of a configurable physiological measurement system embodiment;

FIG. 3 is a detailed block diagram of networked information elements in a configurable physiological measurement system;

FIG. 4 is a flowchart of a physiological measurement system configuration process; and

FIGS. 5A-B are block diagrams illustrating forward and backward sensor compatibility with various processors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In this application, reference is made to many blood parameters. Some references that have common shorthand designations are referenced through such shorthand designations. For example, as used herein, HbCO designates carboxyhemoglobin, HbMet designates methemoglobin, and Hbt designates total hemoglobin. Other shorthand designations such as COHb, MetHb, and tHb are also common in the art for these same constituents. These constituents are generally reported in terms of a percentage, often referred to as saturation, relative concentration or fractional saturation. Total hemoglobin is generally reported as a concentration in g/dL. The use of the particular shorthand designators presented in this application does not restrict the term to any particular manner in which the designated constituent is reported.

FIG. 1 illustrates a configurable physiological measurement system 100 having a processor 110, a sensor 120 and a communications link 130. In one embodiment, the sensor 120 has two or more light emitters that transmit optical radiation of two or more wavelengths into a tissue site and at least one detector that generates a signal responsive to the optical radiation after attenuation by the tissue site. Multiple wavelength sensors are described in U.S. patent application Ser. No. 10/719,928, entitled Blood Parameter Measurement System, assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein.

The processor 110 generates drive signals so as to activate the sensor emitters and inputs and processes the corresponding detector signal so as determine the relative concentrations of two or more blood constituents. The communications link 130 provides communications between the processor 110 and sensor 120 including transmitting the drive signals from the processor 110 to the sensor 120 and the detector signals from the sensor 120 to the processor 110. In one embodiment, the communications link 130 is a cable and corresponding sensor and processor connectors that provide a wired connection between the processor 110 and connector 120. In another embodiment, the communications link 130 provides a wireless connection between the processor 110 and connector 120. The wireless connection may utilize Bluetooth®, IEEE 802.11 or similar wireless technologies.

As shown in FIG. 1, the configurable physiological measurement system 100 also has information elements 112, 122, 132 distributed across the processor 110, the sensor 120 and the communications link 130, which provide system configuration information, as described below. The information elements 112, 122, 132 may be memory devices, such as described below, or other active or passive electrical components. The information provided by the information elements 112, 122, 132 may be digital data stored in memory or component values determined by DC, AC or combinations of DC and AC voltages or currents. The information element 112, 122, 132 information may be determined by the processor 110 or by a reader or other device in communication with the information elements 112, 122, 132 and the processor 110.

FIG. 2 illustrates configurable physiological measurement system embodiments having processor 210, sensor 220 and cable 230 components. In one embodiment, the processor 210 has a processor printed circuit board “board” 212 and an optional daughter board 214, which plugs into and expands the functionality of the processor board 212. For example, the daughter board 214 may be a noninvasive blood pressure (NIBP) controller that communicates with a blood pressure sensor and the processor board 212 so as to measure blood pressure parameters.

Also shown in FIG. 2, in one embodiment the sensor 220 is a “resposable” sensor comprising a reusable portion 222 and a disposable portion 224. In a particular embodiment, the reusable portion has at least one of a reusable emitter portion and a reusable detector portion, and the disposable portion 224 has at least one of a disposable emitter portion, a disposable detector portion and a disposable tape for attaching the reusable sensor 222 to a tissue site. A resposable sensor is described in U.S. Pat. No. 6,725,075 entitled Resposable Pulse Oximetry Sensor, assigned to Masimo Corporation and incorporated by reference herein.

Further shown in FIG. 2, in one embodiment the cable 230 is a patient cable 232 or a sensor cable 234 or a combination of a patient cable 232 and a sensor cable 234. A sensor cable 234 is fixedly attached at one end to a sensor and has a connector at the other end for attaching to a monitor or a patient cable. A patient cable 234 has connectors at both ends for interconnecting a sensor or sensor cable to a monitor.

FIG. 3 illustrates an information element (IE) network 300 that advantageously enables a physiological measurement system 200 (FIG. 2) to be composed of various components 214-234 (FIG. 2) having, perhaps, differing parameter measurement capabilities, as described above. The IE network 300 also allows various components to “plug and play,” i.e. interoperate without hardware or software modification, as described with respect to FIG. 4, below. Further, the IE network 300 provides for forward and backward compatibility between sensors and processors, as described with respect to FIGS. 5A-B, below.

As shown in FIG. 3, the IE network 300 has information elements 314-334, a network controller 301 and a communications path 305. In one embodiment, the network controller 301 resides on or is otherwise incorporated within a processor board 212 (FIG. 2). The information elements 314-334 correspond to the physiological measurement system components 210-230 (FIG. 2). In one embodiment, there may be zero, one, two or more information elements 314-334 on or within each physiological measurement system component 214-224 (FIG. 2). For example, the information elements 314-324 may include a DB element 314 mounted on a daughter board 214 (FIG. 2), a RS element 322 mounted within a reusable sensor portion 222 (FIG. 2), a DS element 324 mounted within a disposable sensor portion 224 (FIG. 2), a PC element 332 mounted within a patient cable 232 (FIG. 2) or connector thereof, and a SC element 334 mounted within a sensor cable 234 (FIG. 2) or connector thereof.

Also shown in FIG. 3, in one embodiment the information elements 314-334 are EPROMs or EEPROMs or a combination of EPROMs or EEPROMs within a particular component 210-230 (FIG. 2). In an advantageous embodiment, the communications path 305 is a single shared wire. This reduces the burden on the components 210-230 (FIG. 2) and associated connectors, which may have a relatively large number of conductors just for drive signals and detector signals when a multiplicity of sensor emitters are utilized for multiple parameter measurements. An information element 314-324 may be, for example, a Dallas Semiconductor DS2506 EPROM available from Maxim Integrated Products, Inc., Sunnyvale, Calif., or equivalent.

FIG. 4 illustrates a configuration process 400 for a physiological measurement system 200 (FIG. 2). This process is executed by the network controller 301 (FIG. 3) or the processor 210 (FIG. 2) or both with respect to information elements 314-334 (FIG. 3) that exist on the network 305 (FIG. 3). After system power-up, any information elements on the network are polled 410 so they identify themselves. Information is then downloaded from the responding information elements 420. In one embodiment, download information can be some or all of Identification (ID), Life, Parameters, Characterization and Features information. ID identifies a component on the network, either the type of component generally, such as a sensor or cable, or a particular part number, model and serial number, to name a few. As another example, ID for a disposable sensor portion 224 (FIG. 2) may be an attachment location on a patient and ID for a reusable sensor portion 222 (FIG. 2) may be a patient type.

Life, for example, may be a predetermined counter written into an EEPROM to indicate the number of uses or the length of use of a particular component. Then, Life is counted down, say each time power is applied, until a zero value is reached, indicating component expiration.

Parameters specifies the measurements the component is capable of supporting, which may include, for example, one or more of SpO₂, HbCO, MetHb, fractional SpO₂, Hbt, NIBP and blood glucose to name just a few. With respect to a sensor, Parameters depend on the number of emitters, emitter wavelength and emitter configuration, for example. For a cable, Parameters depend on the number of conductors and connector pinouts, for example. Parameters may also simply reflect a license to use a component, such as disposable tape, with respect to a particular system configuration.

Features set the mode for the processor or other system elements. As one example, Features specify the mode or modes of one or more algorithms, such as averaging.

Characterization allows the processor to “plug and play” with a particular component. For example, if the component is a sensor, Characterization may include information necessary to drive the emitters, such as the LED wavelengths and drive pattern. Characterization may also include calibration data for the parameters measured. As another example, Characterization for a sensor component 220 (FIG. 2) may indicate sensitivity to a probe-off condition depending on the sensor type. Probe-off detection is described in U.S. Pat. No. 6,654,624 entitled Pulse Oximeter Probe-Off Detector and U.S. Pat. No. 6,771,994 entitled Pulse Oximeter Probe-Off Detection System, both assigned to Masimo Corporation and incorporated by reference herein.

As shown in FIG. 4, components are identified 430 from downloaded ID information. If any of the information elements provide Life information, a check is made to determine if the corresponding component is expired 440. If so, an error message is displayed 480. The message may be a warning to replace the component or it may indicate that the system is nonfunctional. Next, the least common denominator (LCD) of the parameters is determined 450 from the Parameters information. This is described in further detail with respect to FIGS. 5A-B. Characterization is determined 460, if necessary for a particular component, such as a daughterboard or sensor. Finally, the processor is configured 470 and the system is ready to begin parameter measurements.

FIGS. 5A-B illustrate embodiments of a configurable physiological measurement system 100 demonstrating both forward sensor compatibility (FIG. 5A), and backward sensor compatibility (FIG. 5B). Further, the parameter measurement capability of each system 100 is determined by the least common denominator (LCD) of the parameter capabilities of a processor 210 and a sensor 220.

As shown in FIG. 5A, configurable physiological measurement systems 200 comprise a family of processors (P0, P1, P2) 210 including those capable of computing SpO₂ 510-530, HbCO 520-530 and MetHb 530. The systems 200 also comprise a family of sensors 220 (S0, S1, S2) including those capable of detecting SpO₂ 550-570, HbCO 560-570 and MetHb 570. Here, the lower numbered processors and sensors represent less capability, e.g. older generation processors and sensors or current generation, but less costly processors and sensors. Illustrated is forward sensor compatibility, i.e. less capable sensors are capable of running on more capable processors. For example, an SpO₂ only sensor 550 is capable of working with a multiple parameter (SpO₂, HbCO, MetHb) processor 530. Also illustrated is LCD functionality. A system 200 having a P2 processor 530 and a S0 sensor 550 is functional but only capable of measuring SpO₂.

FIG. 5B illustrates backward sensor compatibility, i.e. more capable sensors are capable of running on less capable processors. For example, a multiple parameter (SpO₂, HbCO, MetHb) sensor 570 is capable of working with an SpO₂ only processor 510. Also, a system 200 having a P0 processor 510 and a S2 sensor 570 is functional, but only capable of measuring SpO₂.

Forward and backward sensor compatibility is described above with respect to configurable physiological measurement systems 200 having various processor 210 capabilities and sensor 220 capabilities. The configurable physiological measurement systems 200 can have any or all of the processor 210, sensor 220 and cable 230 components described with respect to FIG. 2, above. As such forward and backward compatibility is equally applicable to combinations of processor 210 and cable 230 or combinations of sensor 220 and cable 230, including the components of such described with respect to FIG. 2, where the capability of such combinations is determined by LCD functionality, as described above.

A configurable physiological measurement system has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in the art will appreciate many variations and modifications.

Claims

1. (canceled)

2. A physiological measurement system comprising: a plurality of components each configured to provide information specifying measurements the components are capable of supporting, at least one of the plurality of components being a sensor configured to transmit light having a plurality of wavelengths into a tissue site and to generate a sensor signal responsive to the transmitted light after tissue attenuation; anda processor configured to receive the information from each of the components and determine, based on the information, which of a plurality of potential physiological measurements the physiological measurement system is capable of supporting.

3. The physiological measurement system of claim 2, wherein the processor is further configured to calculate measurements of at least one of the plurality of potential measurements based on the determination.

4. The physiological measurement system of claim 2, wherein each of the plurality of components are further configured to provide characterization information.

5. The physiological measurement system of claim 4, wherein the characterization information comprises characterization information specific to respective components of the physiological measurement system.

6. The physiological measurement system of claim 2, wherein plurality of components further include at least one of a daughterboard, a patient cable, a sensor cable, a reusable portion of a sensor, or a disposable portion of a sensor.

7. The physiological measurement system of claim 2, wherein the sensor comprises a resposable sensor.

8. A method of a physiological parameter system, the method comprising: providing a plurality of components each configured to provide information specifying measurements the components are capable of supporting, at least one of the plurality of components being a sensor configured to transmit light having a plurality of wavelengths into a tissue site and to generate a sensor signal responsive to the transmitted light after tissue attenuation;receiving, at a processor, the information from each of the components; anddetermining, by the processor and based on the information, which of a plurality of potential physiological measurements the physiological measurement system is capable of supporting.

9. The method of claim 8 further comprising: calculating, by the processor, measurements of at least one of the plurality of potential measurements based on the determination.

10. The method of claim 9 further comprising: configuring the processor so as to enable calculation of measurements of at least one of the plurality of potential measurements based on the information.

11. The method of claim 8, wherein each of the plurality of components are further configured to provide characterization information.

12. The method of claim 11, wherein the characterization information comprises characterization information specific to respective components of the physiological measurement system.

13. The method of claim 8, wherein at least one of the plurality of components is a daughterboard, a patient cable, a sensor cable, a reusable portion of a sensor, or a disposable portion of a sensor.

14. The method of claim 8, wherein the sensor comprises a resposable sensor.

15. A physiological measurement system comprising: a physiological sensor capable of detecting a plurality of physiological parameters of a patient by transmitting light having a plurality of wavelengths into a tissue site of the patient and generating a sensor signal responsive to the transmitted light after tissue attenuation, the physiological sensor configured to provide information specifying measurements the physiological sensor is capable of supporting; anda processor in communication with the physiological sensor, the processor capable of supporting only a subset of the plurality of physiological parameters that the physiological sensor is capable of supporting, the processor further configured to determine, based on the provided information, the supported subset of the plurality of physiological parameters.

16. The physiological measurement system of claim 15, wherein the processor is further configured to calculate physiological measurements corresponding to each of physiological parameters of the supported subset.

17. The physiological measurement system of claim 15, wherein physiological sensor is further configured to provide characterization information.

18. The physiological measurement system of claim 17, wherein the characterization information is useable by the physiological measurement system to configure to the processor to determine measurements of each of physiological parameters of the subset.

19. The physiological measurement system of claim 15, wherein the physiological sensor comprises a resposable sensor.