Patent Grant
9839362
The present invention relates to a finger cuff that integrates an SpO2 sensor with a continuous, non-invasive, arterial blood pressure (CNAP) sensor for non-invasively determining arterial blood pressure and the level of oxygen saturation in blood from a single device.
The “vascular unloading technique” or “volume-clamp method” introduced by Peñaz in the early 1970's provided for a new method to continuously and non-invasively monitor arterial blood pressure (CNAP). Devices exist that include a band that is externally placed over adjacent fingers containing arteries of comparable size. A sensor detects pulsating changes in the arteries based on the amount of light transmitted through the tissue. The transmitted light intensity is used to measure the blood volume under the finger artery. The pressure in the cuff is changed by compression and decompression to keep the blood volume substantially constant. By maintaining a constant blood volume, the arterial wall is relaxed and the cuff pressure is substantially identical to the pressure in the underlying artery. The cuff pressure therefore reflects the intra-arterial pressure under the finger cuff and continuous non-invasive beat-to-beat pressures can be calculated.
In addition to continuous non-invasive blood pressure measurements, obtaining information regarding the blood oxygen saturation level of a patient using a non-invasive monitoring mechanism is desirable in both diagnosis and treatment of medical conditions. Blood oxygen saturation level may be determined using a technique known as transmission spectrophotometry, or more widely known as pulse oximetry (SpO2). Conventionally, pulse oximetry measurements are obtained via a sensor positioned on a finger of the hand having the non-invasive blood pressure monitor connected thereto or on a finger on the contra-lateral hand. A drawback associated with this configuration is increased discomfort to the patient and an increase in the number of sensors connected to the patient making monitoring more costly and cable management more difficult for healthcare professionals. A further drawback is the increased chance that one or more sensors would become dislodged thereby disrupting patient monitoring.
Accordingly, there is a need for a device and a method that permits simultaneous CNAP and SpO2 measurements without increasing the number of separate sensors attached to a patient. In addition, it would also be desirable to provide a cuff design adaptable to the patient's finger circumference, thereby reducing measurement errors related to cuff application and cuff shifting on the finger. A system according to invention principles addresses deficiencies of known systems.
In one embodiment, an apparatus for measuring at least two patient parameters is provided. A first cuff includes a first inflatable bladder, a first light emitting device and a first sensor that senses light data for use in calculating at least two patient parameters. A second cuff includes a second inflatable bladder, a second light emitting device and a second sensor that senses light data for use in calculating the at least two patient parameters. A controller is coupled to the first and second sensors and when the controller causes the bladder of one of the first and second cuffs to inflate, the sensor of the one of the first and second cuffs senses first light data used in determining a first of the at least two patient parameters and the sensor of the other of the one of first and second cuffs simultaneously senses second light data used in determining of a second of the at least two patient parameters.
In another embodiment, a method for simultaneously monitoring at least two patient parameters is provided. The method includes the activities of pressurizing a respective cuff of a cuff pair positioned on adjacent digits of a patient, each cuff of the cuff pair including a light emitting device and sensor that can sense light data for use in determining at least two patient parameters. First light data used in determining a first patient parameter is sensed using the sensor in the respective pressurized cuff and data representing the first patient parameter based on the first light data is determined. Second light data used in determining a second patient parameter is simultaneously sensed using the sensor in the other of the respective cuff, the other of the respective cuff being unpressurized and data representing the second patient parameter based on the second light data is determined. Data representing the first and second patient parameter is output for use by a healthcare professional charged with monitoring the patient.
In a further embodiment, an apparatus is provided that measures at least two patient parameters. The apparatus includes a first cuff including a first inflatable bladder, a first light emitting device emitting a first and second type of light and a first sensor that senses first and second light data for use in calculating at least two patient parameters. A controller coupled the sensor, and when the controller causes the bladder of the first cuff to inflate, the first sensor senses first light data used in determining a first of the at least two patient parameters and simultaneously senses second light data used in determining of a second of the at least two patient parameters.
These and other features and advantages of the present invention will become more readily appreciated from the detailed description of the invention that follows.
The following figures depict certain illustrative embodiments of the invention in which like reference numerals refer to like elements. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way.
The combined CNAP and pulse oximetry (hereinafter, “dual sensor”) apparatus advantageously utilizes a dual finger cuff which alternates blood pressure measurements between respective finger cuffs. When one finger cuff measures SpO2 data the other finger cuff measures CNAP data and vice versa. By combining the measurement of two common medical parameters into a single device, the apparatus advantageously reduces clutter and improves cable management in and around a patient. Moreover, the apparatus enables measurement of key medical parameters while reducing the number of physical sensors connected to the patient. By reducing the number of physical sensors connected to the patient, the apparatus advantageously reduces any instances of erroneous parameter measurement due to a sensor being dislodged from the patient. Reducing the number of physical sensors connected to the patient provides the further advantage of improving patient comfort and mobility while being monitored. The apparatus may also advantageously monitor SpO2 data in both finger cuffs simultaneously. Thus, the cuff measuring CNAP data also measures SpO2 data at the same time while the other cuff only measures SpO2 data. The simultaneous measurement of SpO2 data using both sensors advantageously provides a mechanism for comparison that may be used to identify a medical condition of a patient. Additionally, the simultaneous measurement of CNAP and SpO2 in a single cuff advantageously provides a feedback control mechanism to monitor the effectiveness of the CNAP measurement and modify the CNAP measurement procedure in response to particular SpO2 measurements thereby improving patient comfort and reducing the risk of prolonged venous congestion. The finger cuff may also employ an adjustable cuff selectively securable by hook and loop fasteners, similar to conventional blood pressure cuffs utilized on neonates, which provides a superior patient-specific fit as compared to the conventional rigid cuff enclosure typically employed in stand-alone CNAP and/or SpO2 sensors. The adjustable dual sensor apparatus cuff provides for a cuff design adaptable to the patient's finger circumference and will make the cuff optionally either a single-use or a reusable cuff. Single-use or single patient-use accessories are advantageous in the medical field because they can reduce cross-contamination between patients or between patients and healthcare providers. They are also cost-effective and can reduce the end price of the device and ultimately the cost of the monitoring procedure.
The dual sensor includes two substantially identical pressure cuffs with an inflatable bladder positioned preferably over adjacent fingers. Each of the pressure cuffs also includes a sensor that is able to monitor at least two patient parameters. In one embodiment, the patient parameters may include CNAP data and SpO2 data. The sensor may be a blood volume sensitive sensor, i.e., a SpO2 sensor, capable of measuring blood volume as well as blood oxygen saturation. The sensor may include two light sources, typically one LED emitting light in the red wavelength range and one infrared LED (IR-LED). The sensor may employ both light sources when measuring SpO2 data and one light source (e.g. the LED emitting light in the red wavelength) when measuring CNAP data. The CNAP and SpO2 sensors also include one or more photodetectors, arranged substantially on an opposite side of the cuff relative to the light sources. The same red LED and associated photodetector may be used for both CNAP and SpO2 measurements. The redundancy of sensors greatly reduces the incidence of false warnings and minimizes the cost in producing the apparatus. Redundant sensors also reduce the cost to healthcare enterprises when monitoring patients as well as reducing costs to insurance companies who cover patient costs for patient monitoring during an in-patient stay.
The two finger cuffs may be inflated and pressed into service in regular time intervals alternating between CNAP and SpO2 measurements so that the blood flow in the patient's finger is not constricted for a time period that would cause undue discomfort or tissue damage. Additionally, SpO2 measurements may also be taken on the cuff that is inflated as well as the cuff that is not inflated. Thus, the SpO2 measurement in the inflated cuff may be used to control the inflation in that cuff. This measurement may also be used to control and modify the CNAP algorithm to prevent patient discomfort by automatically alternating between which cuff is inflated. Incorporating into the finger cuff design an SpO2 sensor that uses conventional pulse oximetry technology to provide oxygen saturation values in addition to continuous, non-invasive blood pressure eliminates the need for using an additional digit and hence reduces the number of accessories attached to the patient and improves cable management.
In a method for continuous, non-invasive measurement of blood pressure (CNAP) and blood oxygen saturation level (SpO2), pressure cuffs which can be controllably and separately inflated are placed over two or more fingers, pressure in a first pressure measuring chamber connected to a first of the pressure cuffs is controlled depending on a measurement signal of a plethysmographic sensor device in such a way that a difference between an amplitude of the plethysmographic measurement signal and a predetermined value is minimized, which then provides a blood pressure reading. During the time of the blood pressure measurement in a first cuff, the blood oxygen saturation level is measured with another cuff on another finger not currently used for the blood pressure reading. Because the pressure cuffs include optical emitters and sensors for both blood pressure measurements and SpO2 measurements, the role of the cuffs and their operation can be interchanged, so that in a subsequent measurement, the first cuff is used to measure the blood oxygen saturation level, while the other cuff or cuffs are used to obtain a blood pressure reading.
The device may operate by inflating a first cuff for CNAP measurements, while the SpO2 signal is acquired with the second cuff on the other finger (not inflated). Optionally, a reference pressure measurement is performed first, before the actual blood pressure is measured. CNAP/SpO2 measurements typically have a duration of about 15 minutes, after which time the operation of the cuffs is reversed, i.e. the second cuff is inflated and CNAP measurements are taken with the second cuff, while the first cuff is deflated and used for SpO2 measurements. In this way, both CNAP and SpO2 measurements can be taken with a simple device having two substantially identical cuffs which are preferably interconnected and applied on adjacent fingers.
Devices and methods are described that allow simultaneous continuous, non-invasive arterial blood pressure (CNAP) and SpO2 measurements on two or more, preferably adjacent, fingers.
The plethysmographic sensor devices 5, 5′ each include light emitters 8 and light detectors 9 and are thus able to detect the pulsating changes of the irradiated volume of blood within arteries 2 included in the intra-arterial blood pressure determination therein as well as an oxygenation level of the blood of the patient. In one embodiment, the light emitters 8 in each of plethysmographic sensors 5, 5′ are able to emit a first type of light having a first wavelength and a second type of light that includes successive emission of light in the first wavelength followed by emission of light in a second different wavelength. For example, the emitter 8 may include an LED that emits light in (a) a red wavelength and (b) an infra-red (IR) wavelength. In another embodiment, the emitter may include two discrete LEDs each emitting a particular type of light in a particular spectrum such that one LED emits the light at the first wavelength and the second LED emits light at two different wavelengths (the first wavelength and second wavelength). Additionally, the particular type of light emitted by emitter 8 is described for purposes of example only and the apparatus may employ an emitter 8 that emits any type of light in any wavelength depending on the type of patient parameter to be measured. The emitter 8 may emit a single type of light at any given time or, alternatively two different types of light at a given time. One skilled in the art will recognize that two or more emitters that produce light of wavelengths other than red and infrared may be utilized in either of the embodiments to perform measurements of oxygen saturation other than SpO2 (e.g., hemoglobin (SpHb), oxygen content (SpOC), carboxyhemoglobin (SpCO), or methemoglobin (SpMet)).
The pressure measuring chambers 4, 4′ are connected via pressure lines 13, 13′ to pressure control chambers 12, 12′. Inlet valves 10, 10′ and outlet valves 11, 11′ of the pressure measuring chambers 4, 4′ may be placed, as illustrated, in the separate pressure control chambers 12, 12′. The inlet valves 10, 10′ selectively connect a pressure source 14 with the pressure control chambers 12, 12′. The outlet valves 11, 11′ selectively connect the pressure control chambers 12, 12′ with the pressure lines 13, 13′. Alternatively, the outlet valves 11, 11′ may be positioned between the pressure lines 13, 13′ and the pressure measuring chambers 4, 4′. Pressure is provided from the pressure source 14, through inlet valves 10, 10′ and received in the pressure control chambers 12, 12′. At predetermined intervals, the outlet valves 11, 11′ are selectively opened allowing pressure to flow through the pressure lines 13,13′ and into the pressure measuring chambers 4, 4′ thereby pressurizing the cuff 1, 1′. Alternatively, the pressure measuring chambers 4, 4′ may be combined into a single chamber (not shown).
In one embodiment, the two pressure cuffs 1, 1′ may be connected by a connecting element 15, forming a double finger cuff. The pressure chambers 4, 4′ are each provided on the inside with an easily distensible inner wall membrane 16, 16′. Prior to measurement, the two pressure chambers 4, 4′ of the double finger cuff are slipped onto adjacent fingers 3, 3′, whereby the light emitters 8 and light detectors 9 are automatically positioned adjacent at least one blood vessel. The valves 10, 11 and 10′, 11′ of the pressure control chambers 12, 12′ are controlled, for example, by a controller 6. The pressure cuffs 1, 1′ may be formed from a non-rigid material that allows for the diameter of the cuff 1, 1′ to be selectively modified by a user when affixing the cuff 1, 1′ to the patient. The non-rigid, selectively modifiable diameter of the cuffs 1, 1′ advantageously enable a patient specific fit of the cuff 1, 1′ each time the cuffs 1, 1′ are connected to the user. Further, the non-rigid material from which the cuffs 1, 1′ are made enables the sensors 5, 5′ to be positioned more precisely with respect to the arteries in the body part to which the cuffs 1, 1′ are connected. This advantageously provides more precise parameter measurements while minimizing monitoring errors resulting from an imprecise fit of the rigid cuffs that are conventionally used to monitor patient parameter data. An example of non-rigid cuffs 1, 1′ is shown in
A controller 6 is selectively connected to pressurize the pressure measuring chambers 4, 4′ and may be used to run different control tasks, for example, alternatingly using the pressure source 14 to inflate one of the pressure measuring chambers 4, 4′. The controller 6 may also control the light emitters 8 and the light detectors 9 for CNAP as well as SpO2 measurements. The controller 6 may also control a display unit 17 and an alarm unit 18. A temperature sensor 20, 20′ may also be placed in or on the chamber walls of each cuff 1, 1′. The operation of the controller 6 and the tasks controlled thereby will be discussed below with respect to
Turning now to
The blood volume sensitive (plethysmographic) sensors 26, 26′ for the measurement of blood oxygen saturation may be positioned distal to the pressure measuring cuffs 22, 22′ (a first embodiment shown on the index finger in
In the first embodiment, conventional pulse oximetry is used and a light emitter 25, 25′ with red and infrared LEDs and a corresponding photodetector 27, 27′ are incorporated into the sensors 26, 26′. The first embodiment uses both IR and red light sources, with the sensors 26, 26′ being placed distal to the cuff 22, 22′. While the pressure cuff 22, 22′ is inflated, the IR light source 25 incorporated in the sensor 26, 26′ is used to acquire measurements of blood volume. Current CNAP technology utilizes an infrared light source in the pressure cuff to measure blood volume and to control cuff pressure to maintain a constant blood volume. As cuff 22 is inflated, the IR light source is used to measure CNAP data in cuff 22. Simultaneously, cuff 22′ is not inflated and the IR and red light sources 25′ incorporated in the sensor 26′ of cuff 22′ are used to acquire measurements of oxygen saturation (SpO2). Conversely, when cuff 22′ is inflated, sensor 26 in cuff 22 is used to measure SpO2.
In the second embodiment, the light emitter 25, 25′ and photodetector 27, 27′ are incorporated into the cuff bladder 24, 24′. The pressure measuring cuffs 22, 22′ are each equipped with a light emitter 25, 25′ that incorporates both red and IR light sources and a corresponding light detector 27, 27′ that are incorporated at locations selected to increase the likelihood of placement over arteries in the finger. The IR LEDs incorporated into the emitters are the same as those already employed in pulse oximetry. Therefore, this embodiment includes both red and IR light sources utilized in conventional pulse oximetry, i.e., the IR LEDs are used for both oximetry and CNAP measurements. Similar to the first embodiment, while cuff 22 is inflated, the infrared light source 25 and sensor 27 in cuff 22 is used to acquire measurements of blood volume and the sensor 27′ incorporated in cuff 22′ is used to acquire measurements of oxygen saturation. The exemplary device of the invention using the hook and loop fastener for adjusting the size of the finger cuff prevents the cuff from sliding upward over the phalangeal joints, thereby reducing measurement errors.
With the above design, it would be beneficial to first complete sensor attachment before the position of a pressure cuff 22, 22′ is adjusted around the finger, thus avoiding the phalangeal joints. In this way, the light emitter 25, 25′ and light detector 27, 27′ in the pressure cuff are optimally positioned over the respective finger.
In one exemplary embodiment, the device may incorporate separate cuff controller cables 13, 13′ and 23, 23′ (see also
Additionally, the apparatus may include a plurality of fittings and connectors to allow the finger cuff and sensor to be disconnected from the cuff controller cable. This will facilitate the use of disposable cuffs. Additionally, the cuff controller cable may be disconnected from the CNAP/SpO2 measuring device.
The controller 6 selectively controls the pressure within the pressure measuring chamber 4, 4′ as well as the operation of the sensor units 5, 5′. The controller 6 may include a parameter processor 300 that selectively controls the monitoring of at least two patient parameters. The parameter processor 300 may include a CNAP processor 302 that selectively controls the sensor units 5, 5′ to sense an arterial pressure within the part of the body to which one of the respective cuffs 1, 1′ is attached. The manner in which arterial pressure is measured by the apparatus may employ the vascular unloading technique and is well known in the art. The parameter processor 300 may also include an SpO2 processor 304 that selectively controls the sensor units 5, 5′ to sense data representing a blood oxygen saturation level of the patient. The SpO2 processor 304 employs pulse oximetry techniques that are known in the art in order to derive the blood oxygen saturation level of the patient by sequentially passing light at the first wavelength and light at the second wavelength through the part of the body to which the cuff 1, 1′ is connected. By sequentially passing two different wavelengths of light through the body, the detector 9b, 9b′ is able to determine the ratio of changing absorbance of the two different wavelengths of light caused by the difference in color of oxygenated versus deoxygenated hemoglobin in the blood. The description of the parameter processor 300 including both the CNAP processor 302 and SpO2 processor 304 as being separate processors is described for purposes of example only and to clearly espouse the operation and function of each. One skilled in the art would understand that the arterial pressure monitoring and blood oxygen saturation monitoring maybe performed by a single processing device. For purposes of ease of understanding, the discussion of the parameter processor 300 should be understood as including any one of the CNAP processor 302 and SpO2 processor 304, or the combination thereof unless specified otherwise.
The parameter processor 300 is shown being directly connected to the cuffs 1, 1′ for purposes of simplicity and clarity. However, one skilled in the art will appreciate that the CNAP processor 302 and the SpO2 processor 304 may each be connected directly to the sensor units 5, 5′ and, more specifically, may be connected directly to first sensors 301, 301′ and/or second sensors 303, 303′ enabling direct control over the particular sensors that make up the sensor units 5, 5′. Thus, the parameter processor 300 may selectively receive and process data sensed by the sensor units 5, 5′ in order to derive arterial pressure data and blood oxygen saturation data therefrom. Alternatively, in order to minimize circuit complexity, the controller 6 may employ a multiplexer to connect the patient parameter processor 300 to the sensor units 5, 5′ in cuffs 1, 1′.
A memory 306 may be connected to the parameter processor 300. The memory 306 includes a data storage medium able to store at least one of analog or digital data therein. The CNAP processor 302 and the SpO2 processor 304 selectively cause data derived from respective sensor units 5, 5′ including arterial pressure data and blood oxygen saturation data to be stored in the memory 306 at predetermined time intervals for predetermined durations. The CNAP processor 302 and SpO2 processor 304 may selectively query data stored in memory 306 at predetermined intervals in order to determine if the respective parameter monitoring algorithm employed by the CNAP processor 302 or SpO2 processor 304 should be modified in any manner as will be discussed below.
A communication processor 310 may also be selectively coupled to the parameter processor 300. The parameter processor 300 may generate control signals that control the communication processor 310 to selectively communicate data to at least one of a display unit 17, an alarm unit 18 and to a remote computing system 314 via a communications network 312. The data communicated by the communication processor 310 may include any data sensed or derived by the parameter processor 300 including arterial blood pressure data and blood oxygen saturation data. In one embodiment, arterial blood pressure data and blood oxygen saturation data may be selectively communicated at least one of (a) simultaneously; (b) sequentially; (c) in response to the parameter processor 300 determining that a type of data has reached, exceeded, or fallen below a threshold value; and (d) in response to receipt of an external request (user generated or automatically generated by a computing system) requesting a particular type of data be transmitted. In another embodiment, the parameter processor 300 may generate a control signal causing the communication processor 310 to query and communicate data stored in memory 306. In this embodiment, the communication processor 310 may cause a set of data sensed by sensor units 5, 5′ and that is stored in memory 306 to be selectively communicated via network 312 to a remote computing system 314 (e.g. hospital information system) to automatically update a patient record with arterial blood pressure data and blood oxygen saturation data at a particular time interval. The communication processor 310 may also be able to selectively receive control requests from remote computing systems 314 (or users thereof) that selectively modify the operation of the apparatus. In a further embodiment, the patient parameter processor 300 may automatically and in real-time compare patient parameter data to threshold parameter values and, if the sensed patient parameter data at least one of (a) equals a threshold; (b) exceeds a threshold; and (c) falls below a threshold, the patient parameter processor 300 may selectively control the communication processor 310 to signal at least one of the display unit 17 or alarm unit 18 to notify a healthcare professional that the patient may be in trouble and require assistance.
The controller 6 may also include a pressure processor 308 that may be connected to the parameter processor 300. The pressure processor 308 may selectively monitor the pressure in the pressure measuring chambers 4, 4′ of cuffs 1, 1′ in order to obtain at least one of arterial pressure data and blood oxygen saturation data. The pressure processor 308 may also be selectively connected to the pressure source 14 for controlling an amount of pressure that is provided to respective pressure measurement chambers 4, 4′. The pressure processor 308 is shown for purposes of example only and one skilled in the art would understand that the parameter processor 300 may selectively perform any and all functions performed by the pressure processor 308 including measuring a pressure level in respective cuffs 1, 1′ and controlling the pressurization of the cuffs 1, 1′ via the pressure source 14.
In a first mode of operation, the CNAP processor 302 signals the pressure processor 308 to pressurize the pressure measurement chamber 4 in cuff 1 in order to obtain arterial pressure data from the finger on which cuff 1 is positioned. The CNAP processor 302 automatically causes the first emitter 8a in cuff 1 to emit the first type of light (red wavelength). The first type of light passes at least partially through the finger and arteries contained therein and a remaining amount of the first type of light is detected by detector 9a. The amount of the first type of light detected by detector 9a is provided to the CNAP processor 302 in order to (a) based on the pulsatile nature of arterial blood flow, selectively control the pressure processor 308 to modify a pressure level in the pressure measurement chamber 4 until a pressure level in the chamber 4 is equal to the mean pressure level in the arteries of the finger and (b) calculate the arterial pressure value based on the sensed amount of first type of light detected by detector 9a and the corresponding pneumatic pressure within cuff 1. The CNAP processor 302 selectively monitors arterial pressure data in this manner over a predetermined time period (e.g. between 30 and 60 minutes).
Also during the first mode of operation, cuff 1′ is not pressurized and the SpO2 processor 304 causes the at least one of emitter 8b′ of the sensor unit 303′ to emit the second type of light that includes a sequential emission of a pulse of light at the first wavelength and a pulse of light at the second wavelength. The second type of light passes through the finger on which cuff 1′ is positioned. The detector 9b′ is able to selectively detect an amount of the second type of light that passes through the finger in cuff 1′. Values corresponding to an absorbance of the first wavelength of light and the second wavelength of light passing through the finger are provided to the SpO2 processor 304 to selectively determine blood oxygen saturation level for the patient in a known manner.
At the expiration of the predetermined time period, the CNAP processor 302 causes the pressure processor 308 and pressure source 14 to depressurize the chamber 4 in cuff 1 and automatically pressurize the pressure measurement chamber 4′ in the second cuff 1′ and use the second cuff 1′ to determine arterial pressure data for the patient. Upon determining that the second cuff 1′ is being pressurized, the SpO2 processor 304 automatically uses the emitter 8b and detector 9b to derive blood oxygen saturation data. Thus, in the first mode of operation, the type of parameter being monitored by a respective cuff alternates between arterial pressure monitoring and blood oxygen saturation monitoring and each cuff 1, 1′ is charged with measuring a single patient parameter. Generally, the operation of the first mode is time based and cuff pressurization alternates at fixed intervals. However, any of the CNAP processor 302 or SpO2 processor 304 may selectively and continually monitor data sensed by the sensing units and automatically switch which of cuff 1 or 1′ is being pressurized at a given time in response to at least one of arterial pressure data and blood oxygen saturation data.
Also in the first mode of operation, the data derived by the CNAP processor 302 and the SpO2 processor 304 may be selectively stored in memory 306 and communicated by communication processor 310 to the remote computing system 314 via the communication network 312. The communication processor 310 may also receive a signal causing the predetermined time period to end prematurely in response to at least one of the arterial pressure data, blood oxygen saturation data or a combination thereof.
The controller 6 may operate in a second mode as well. The second mode of operation is similar to the first mode of operation with one difference. In the second mode of operation, the cuff 1, 1′ that is pressurized measures both arterial pressure data and blood oxygen saturation data. Exemplary operation in the second mode will be discussed with respect to cuff 1 being pressurized as described above. In addition to the CNAP processor 302 causing emitter 8a to emit the first type of light which is detected by detector 9a, the SpO2 processor 304 causes emitter 8b to emit the second type of light which is detected by detector 9b. A value corresponding to arterial blood pressure is derived by the CNAP processor 302 in response to the absorbance of the first type of light detected by detector 9a and a value corresponding to blood oxygen saturation level is derived by the SpO2 processor 304 in response to the absorbance of the second type of light detected by detector 9b.
Alternatively, in an embodiment where a single light emitter and detector is present, the light emitter is able to selectively and sequentially emit light at first wavelength (e.g. red) and a second wavelength (e.g. IR). In this embodiment, the absorbance of the light of a first wavelength as detected by the detector is used by both the CNAP processor 302 to calculate arterial pressure data and the SpO2 processor 304 as part of the calculation of blood oxygen saturation level. In the embodiment with the single light emitter, once the absorbance of light having the first wavelength is detected, the emitter emits the light having the second wavelength and the absorbance of the light having the second wavelength is detected by the detector and provided to the SpO2 processor 304 to be combined with absorbance of the first wavelength of light in order to complete the calculation of blood oxygen saturation data in the known manner.
In another embodiment, blood oxygen saturation data is used to selectively control and/or modify the operation of the CNAP processor 302 and the algorithm employed thereby to monitor arterial pressure. In this embodiment, blood oxygen saturation data may be derived from either the pressurized cuff or the unpressurized cuff. For example, the venous blood oxygen saturation level within the finger being pressurized by cuff 1 may fall below a threshold level indicating that pressurization has occurred for too long and may be causing the patient discomfort. This determination may be made because red light absorption increases as the hemoglobin in the blood becomes more deoxygenated causing an amount of red light detected by the detector 9 to decrease. The decrease in an amount of red light detected by the detector 9 may be indicative of venous congestion in the finger being pressurized by cuff 1 and therefore may indicate that the pressure being applied thereto is either too great in magnitude or too prolonged thus causing the CNAP processor 302 to signal the pressure processor 308 to at least one of (a) automatically modify the pressure of the pressurized chamber 4 and (b) depressurize the chamber 4 and pressurize chamber 4′ in the second cuff 1′.
Furthermore, in the second mode of operation, two values corresponding to blood oxygen saturation level are determined by the SpO2 processor 304. One is derived from the pressurize cuff and is used to selectively control the operation of the CNAP processor 302 and the second, which is derived from the non-pressurized cuff is determined as discussed above in the first mode of operation.
While the explanation of the single cuff feedback control mechanism is described with reference to the absorption of red light, one skilled in the art would understand that the result of the oxygen saturation data may be plotted and would yield a similar result thus causing the controller to automatically depressurize a first cuff and pressurize the second cuff.
Second light data used in determining a second patient parameter is sensed in step 606 using the sensor in the other cuff, the other cuff being unpressurized. In one embodiment, the activity of sensing in step 606 includes emitting a second type of light from a light source, the second type of light including a pulse of light having a first wavelength and a pulse of light having a second wavelength. Successive pulses of light having the first wavelength and second wavelength are passed through a digit of a patient and amounts of the second type of light that has been absorbed by the digit of the first patient are detected. Data representing the second patient parameter is determined based on the sensed second light data in step 608. In one embodiment, the determination made in step 608 may be based on absorption data sensed by the sensor and provided to a processor.
In step 610, the respective cuff of the cuff pair is automatically depressurized after a predetermined time period and second light data in the respective cuff is sensed in step 612 and used for determining the second patient parameter. In step 614, the other cuff of the respective cuff pair is automatically pressurized and first light data for use in determining the first patient parameter is sensed in step 616.
The adjustable dual cuff sensor apparatus advantageously employs a light emitter and corresponding sensor that is able to sense light data that may be used in automatically determining at least two patient parameters including intra-arterial blood pressure and blood oxygenation saturation levels. This is advantageously accomplished by sensing one of the parameters in a first cuff that is in a pressurized state and simultaneously sensing the other parameter in the second cuff that is not pressurized. The respective states of pressurization are alternated such that patient discomfort is minimized without disrupting patient parameter monitoring. This occurs by automatically switching the type of parameter being monitored by a respective cuff based on the pressurization state of the cuff. Additionally, the apparatus advantageously enables sensing and determining of both patient parameter values when a respective cuff is in a pressurized state, the data from the simultaneous intra-cuff determination may be used to further control operation of the apparatus.
While the invention is receptive to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not limited to the particular forms or methods disclosed, but to the contrary, the invention is meant to cover all modifications, equivalents, and alternatives falling with the spirit and scope of the disclosed subject matter.
This application is a National Stage Application under 35 U.S.C. 371 of PCT application PCT/2011/064416, filed Dec. 12, 2011 which claims priority from U.S. Provisional Patent Application Ser. No. 61/426,679 filed on Dec. 23, 2010 by Donald Fournier. The disclosures of the aforementioned applications are hereby incorporated by reference herein in their entireties.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2011/064416 | 12/12/2011 | WO | 00 | 6/18/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2012/087634 | 6/28/2012 | WO | A |
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| Number | Date | Country | |
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| 20140114152 A1 | Apr 2014 | US |
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| 61426679 | Dec 2010 | US |
