Wireless patient monitoring system

A device and method for monitoring a patient having a sensing device taking sensor data continuously and a transmitter located on the patient and internally powered. The transmitter is normally in a power-down state and powered-up for transmitting the sensor data. A receiver is located remote from the patient and receives the sensor data transmitted wirelessly from the transmitter. The transmission is typically a burst and can also be initiated on a command. For the burst, the sensor data is accumulated over a first period. The transmitter can transmit the sensor data over a second period of time. The second period of time is shorter than the first period of time. Once the transmission is complete, transmitter can be powered down. A further step displays the sensor data at the receiver in pseudo real-time. The display is shifted by a sum of the first and the second period of time.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system and method for measuring, storing and communicating sensor readings from a patient to a central system for display and analysis.

2. Discussion of the Related Art

For certain medical conditions, such as head trauma, it is necessary to place sensors on and in a patient to take continuous sensor readings. One shortcoming of the prior art is the need to wire the sensors to receiving and recording units located near the patient. The wires, especially leading to implanted sensors, cause difficulty for caregivers to move and treat the patient, both in and out of bed. In response, wireless sensor systems were developed that record the sensor data and do not tether the patient to wired receivers. The sensor data is transmitted wirelessly to the receiver. However, continuous wireless data transmission draws a significant amount of power. Since the sensors are wireless, they must rely on battery power and the continuous wireless transmission shortens the battery life and thus the operational life of the sensor.

To overcome some of the above shortcomings, U.S. Pat. No. 4,519,401 to Ko et al. (“Ko”) discloses a minimized “pulse” power scheme wherein the sensors and transmitters are placed in a low power cycle when readings are not being taken and then pulse powered up to take a sensor reading and transmit it to a receiver. This power conservation scheme is useful for sensor readings that are only taken at intervals and not continuously. Continuous data sampling would defeat Ko's pulse power scheme, as the sensors and transmitter can never power down.

U.S. Pat. No. 6,533,733 to Ericson et al. (“Ericson”) discloses a sensing system wherein the sensor readings are continuously read and stored. The stored data is then periodically transmitted to a receiver. The sensors are continuously powered and transmitter is also continuously powered and draws additional power during power transmission. Ericson realizes that this system is power consumptive and solves the problem by using a combination of power supplies. Ericson is silent regarding powering down the system and Ericson's system could not take continuous readings without constant power. Further, since Ericson's sensor data is stored, the sensor readings are not resented to the caregiver in approximately real-time. Thus, there is a time lag between when the sensor data is taken and displayed. Ericson compensates for this lag by providing the sensor controller with an alarm function to notify a caregiver of an anomalous sensor reading.

U.S. Pat. No. 6,731,976 to Penn et al. (“Penn”) discloses a passive sensing system wherein sensor readings are taken and transmitted only when powered externally. The sensing and transmission only last as long as the external power is supplied. This embodiment provides “real-time” sensor data but only while the system is externally powered. Further, Penn discloses an embodiment of providing a power supply for the system but, as Ericson does, Penn takes and stores the sensor data but does not disclose powering down the transmitter to conserve energy. Further, Penn does not disclose how to compensate for the lag between when the sensor data is taken and when it is transmitted.

Thus, there is a need in the art for a sensor system that can take continuous readings and provide the sensor data to a caregiver is pseudo-real-time. Further, there is a need to conserve power of the sensing device and transmitter by powering down the transmitter and transmitting the sensor data only over bursts.

SUMMARY OF INVENTION

A device for monitoring a patient sensor has a sensing device disposed on or in the patient and takes sensor data continuously. A transmitter is located on the patient and internally powered. The transmitter is normally in a power-down state and typically only powered-up for transmitting the sensor data. A first link if formed between the sensing device and the transmitter so the transmitter can receive the sensor data. The first link can include a wired and a wireless link. Further, the wireless transmission can be sent over any known wireless frequencies and utilize any protocols known in the art. A receiver is located remote from the patient and receives the sensor data transmitted wirelessly from the transmitter. The transmission is typically a burst and can also be initiated on a command.

A method of monitoring a patent sensor having the steps of acquiring sensor data from the sensing device and linking the sensor data to the transmitter. The transmitter is powered internally and located on the patient. Typically, the transmitter is powered down in a normal state and powered up to transmit the sensor data from the transmitter to a receiver, which is disposed remote from the transmitter. The transmission can be sent by a burst or upon command.

Another embodiment of the present method includes acquiring sensor data from the sensing device. Typically sensor data is acquired continuously, but can also be taken at intervals. The sensor data is linked to a transmitter by the first communication link and the transmitter is powered internally by a power supply. The sensor data is accumulated over a first period of time which can be a few seconds to a few minutes and, in one embodiment, is a one minute interval. The transmitter can be powered-up and transmitting the sensor data from the transmitter to the receiver over a second period of time. The second period of time is shorter than the first period of time and is typically a factor of shorter. Once the transmission is complete, transmitter can be powered down. A further step displays the sensor data at the receiver in pseudo real-time. The display is shifted by a sum of the first and the second period of time. For example, if the sensor data is accumulated over 1 minute and the burst transmission is 6 seconds, the displayed data is time shifted (or lagged) 66 seconds from real-time.

In a further embodiment, the sensor data can be compressed prior to transmitting the sensor data and then it can be decompressed prior to the displaying the sensor data. Compressing the sensor data can assist in shorting the second period of time and thus shortening the burst period and the lag time.

One or more sensing devices can be linked to a single transmitter. Each sensing device can include a unique sensing device ID which identifies each sensing device. The unique sensing device ID can include the serial number of the sensing device and an identifier to identify the type, model, manufacturer and calibration information of the sensing device. The unique sensing device ID can identify the sensing device for the transmitter. Furthermore, the transmitter can have a unique transmitter ID identifying the transmitter to a receiver and the receiver can also have a unique receiver ID. Receiver ID identifies the receiver to a central server and the sensor data can be encoded/encrypted with the unique receiver ID as outlined above regarding the other unique IDs.

In one embodiment, the receiver is located within 15 feet of the transmitter. The proximity of the receiver to the transmitter can prolong the life of power supply because less power is needed if the transmission is over a short distance. Also, the proximity prevents dropped signals and interference from outside sources.

In another embodiment, the sensor data can be encrypted before it is transmitted wirelessly to prevent unauthorized access or tampering with the sensor data. In a further embodiment, one or both of the unique sensing device ID and the transmitter ID can be used as base keys for encrypting the data. The IDs can be used as a public key and thus either every sensing device's or transmitter's sensor data can be uniquely encrypted.

Further to the above, the first link can include a power link to provide power to the sensing device from the transmitter. The receiver can send a confirmation signal to the transmitter to acknowledging receipt of the sensor data. The confirmation signal is a safety feature to assure that the sensor data is received by the receiver.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, a system100for monitoring a patient sensor is illustrated. The system100includes a sensing device102disposed on the surface of or implanted in the patient10that takes sensor data104. The sensing device can be disposed or implanted anywhere on the patient10, including implanted in the patient's brain. Sensing device102can be any medical sensing device, including a pressure sensor, an oxygen sensor, neural impulse sensor, temperature sensor, pH sensor, an electroencephalogram and a fetal heart monitor. The sensing device102can collect sensor data104over many different time periods. Sensor data104can be collected continuously, over either a predetermined or random interval, or upon a command issued from a caregiver. Sensing device102can be powered internally by, for example, disposable batteries, rechargeable batteries, or a capacitive device capable of storing energy transmitted through an inductive power coupling or directly through the inductive power coupling.

Sensing device102transmits the sensor data104to a transmitter106located outside the patient10. The transmitter106is typically located on or very close to the patient10but not implanted in the patient10. Typically, transmitter106can be strapped to the nearest appendage or adhered to the patient's skin. Transmitter106is internally powered by power supply108. Power supply108can be, for example disposable batteries, rechargeable batteries, or a capacitive device capable of storing energy transmitted through an inductive power coupling.

The transmitter106receives the sensor data104over a first link110between the sensing device102and the transmitter106. The first link110can be a wired110aor a wireless link110b. If the first link110is wired link110a, the transmitter106can have multiple leads or ports to accept one or more wired links. The leads and ports can be any type known in the art to transmit at least analogue or digital data to allow the transmission of sensor data104to the transmitter106. If the first link110is a wireless link110b, the transmission can be sent over any known wireless frequencies and utilize any protocols known in the art. Further, wireless link110bcan be transmitted inductively by using the patient's body at the antenna.

Further, the sensing device102and the transmitter106can undergo handshake protocols to “introduce” the sensing device102to the transmitter106. The handshake can be performed automatically upon the powering up or the plugging in of either the sensing device102or the transmitter106. Alternately, the caregiver can initiate a handshake protocol manually.

One or more sensing devices102can be linked to a single transmitter106. Each sensing device102can include a unique sensing device ID which identifies each sensing device102. The unique sensing device ID can include the serial number of the sensing device102and an identifier to identify the type, model, manufacturer and calibration information of the sensing device102. The unique sensing device ID can identify the sensing device102for the transmitter106. Furthermore, the transmitter106can have a unique transmitter ID identifying the transmitter106to a receiver112.

Transmitter106transmits the sensor data104to receiver112. Receiver112is typically located remote from the patient10. In one embodiment, the receiver112is located within 15 feet of the transmitter. The proximity of the receiver112to the transmitter106can prolong the life of power supply108because less power is needed if the transmission is over a short distance. Also, the proximity prevents dropped signals and interference from outside sources.

The receiver112and the transmitter106communicate wirelessly, thus allowing patient10the freedom to move around and shift position or be moved to aid caregivers activities without disrupting the communications between the two. The communication between the transmitter106and the receiver112can take place continuously, at an interval, or upon a command. The interval can be either predetermined or random and in one embodiment, the transmitter106provides a burst transmission at least every minute. Burst transmissions are used to conserve the power of the transmitter106. Sending the transmission to the receiver112is power consumptive and minimizing the number of transmissions can extend the life of the internal power supply108. Short interval bursts allow a caregiver to receive nearly real-time sensor data104and still conserve the power supply108.

Further, transmitter106can process sensor data104through a compression algorithm to compress the data before transmitting it to receiver112. Compressing sensor data104allows for a shorter burst period and assists in reducing the overall power consumption of the transmitter106and prolong the life of the power supply108. Compressed sensor data104also conserves storage space on the receiver112or server114. Compressed sensor data104can be stored compressed and decompressed for processing or display to the caregiver. Alternately, the receiver can decompress the sensor data104upon receipt and store it decompressed to reduce the wait time for processing or displaying.

Further, the wireless transmission can be sent over any known wireless frequencies and utilize any protocols known in the art. Additionally, the transmitter106and the receiver112can undergo handshake protocols to “introduce” the transmitter106to the receiver112. The handshake can be performed automatically upon the powering up or the plugging in of either the transmitter106or the receiver112. Alternately, the caregiver can initiate a handshake protocol manually.

In an embodiment, transmitter106communicates with receiver112utilizing a “burst mode.” Burst mode collects and stores sensor data104in the transmitter106over a set period of time. Typically, the sensor data104is compressed to reduce the size of the data packet. Transmitter106, at the predetermined time, powers up and transmit the stored sensor data104in a burst that is typically much, much shorter than the time period over which the sensor data104is collected. Transmitter106then powers down. The receiver112receives and collects the sensor data104from the transmitter106and decompresses the sensor data104back to the original timescale for display or analysis. The receiver112displays the data in pseudo real-time—the sensor data104is displayed in the same spatial resolution that it was collected with but delayed from real-time by the length of the time period over which it was originally collected plus the communications “burst” time. This embodiment allows transmitter106to limit the power expenditure overhead of powering on and establishing link110by not requiring the transmitter106to perform these tasks for each individual sensor reading taken.

The receiver112can be powered by any source, but typically is powered externally, i.e. plugged into the nearest electrical outlet. In an embodiment, receiver112can be designed as a permanent or semi-permanent device in the patent's room. Utilizing an external power source to power receiver112has advantages. Receiver112can be active continuously and can perform storage, analysis, and display functions. Receiver112can store and accumulate sensor data104for an extended period of time and can store sensor data104from numerous transmitters106and/or patients10. Receiver112can analyze the sensor data104and display it for the caregiver. Additionally, an external power supply allows receiver112more flexibility in communicating the sensor data104, analyzed or not, to a central server114located remote from the receiver112.

Receiver112and central server114can be linked directly or through a network, LAN, WAN, or the Internet. The connection can be wired or wireless using any protocols known in the art. Central server114can be remote from the receiver, i.e. in another room, building or state and a patient10can be monitored by a caregiver remote from the patient's location.

In an embodiment, central server114can be a portable device (e.g. PDA, cell phone, beeper, Blackberry®) or a semi-portable device (laptop and desktop on wheels) that can be carried by the caregiver or kept in proximity to patent10so the caregiver can move into proximity with the patient10and display the sensor data104at, for example, the patient's bedside. Central server114can also store, analyze, and display the sensor data104. In an embodiment, either the receiver112or the central server114analyzes the data, or receiver112can perform basic analysis and central server114performs more detailed analysis if required.

Receiver112can also send notifications to central server114in response to a number of preset or programmed conditions. For example, if the sensor data104shows that there is a critical condition (e.g. the patient's heart stops beating) a notification can be sent (e.g. messaging a pager, ringing a cell phone) notifying the caregiver of the critical condition. As described below, the caregiver can then issue remote instructions to further monitor the patient10.

If the receiver112and the central server114communicate wirelessly, all the protocols, handshake procedures and frequencies described above can be used here as described above.

In an embodiment, sensor data104can be encoded with the unique sensing device ID and the encoded sensor data is transmitted to the receiver112and to the central server114. Using the unique sensing device ID can identify the specific sensor and thus the specific patient10. This can help the organization of the sensor data104when stored and can assist in the search and retrieval of the sensor data104at a later time. Further, sensor data104can be encoded with the unique transmitter ID alone or in combination with the unique sensing device ID. The unique transmitter ID can further assist in storage, searching and retrieval.

In one embodiment, the sensor data104can be encrypted before it is transmitted wirelessly to prevent unauthorized access or tampering with the sensor data104. In a further embodiment, one or both of the unique sensing device ID and the transmitter ID can be used as base keys for encrypting the data. The IDs can be used as a public key and thus either every sensing device's or transmitter's sensor data104can be uniquely encrypted.

Further to the above, the first link110can include a power link to provide power to the sensing device102from the transmitter106. In this embodiment, sensing device102does not have a stand alone power supply. If first link110is wired110a, the power can be transmitted directly to the sensing device102along the same wire or a different wire than the sensor data104is transmitted. Alternately, the power link can be an induced connection. An induction coil from the transmitter106can be placed in proximity to an inductance coil in the sensing device102to provide power to the sensing device102. Power supply108can provide continuous power or act as a charging station to charge the sensing device102on demand. This can be used especially with implanted sensing devices102. Since transmitter106is disposed outside of patient10, it is easier to recharge power supply108and use the transmitter to power sensing device102.

In an embodiment, transmitter106includes a first memory116that temporarily stores the sensor data104prior to the transmission to the receiver112. The first memory116can be flash RAM or any other type of permanent or removable memory known in the art. First memory116can be kept small to allow transmitter106to be light weight. Once the sensor data104stored on first memory116is transmitted to the receiver112, the sensor data can be erased or overwritten. The overwriting procedure can include overwriting the oldest data first.

Additionally, receiver112can include a confirmation signal118transmitted from the receiver112to the transmitter106to acknowledging receipt of the sensor data104. The confirmation signal118is a safety feature to assure that the sensor data104is received by the receiver112. The confirmation signal118can also be used as a trigger for the transmitter106to erase the first memory116.

In an embodiment, if the transmitter106does not receive the confirmation signal118, the transmitter106can repeat the transmission one or more times until the confirmation signal118is received. Also, the transmitter106can include an alarm120that can send an alarm signal when the confirmation signal118is not received once or for a period of time.

Alternately, transmitter106can resend the “old” sensor data104from the unconfirmed transmission as an add-on to the next transmission of “new” sensor data104. If the transmitter106is set to burst transmissions, adding-on sensor data104can lengthen the transmission time but maintains the interval so keep power consumption at a minimum.

In another embodiment, transmitter106can be used to communicate with sensing device102. First link110can provide an instruction to the sensing device102. Examples of instructions can be to turn on/off, change data retrieval intervals, perform a diagnostic test, report power and/or communication status and to take sensor data essentially contemporaneous with the instruction. This allows a caregiver to receive real-time sensor data104, if the caregiver deems it necessary. The instructions can be originated at the transmitter106or at the receiver112and/or central server114to be transmitted to the transmitter106to be relayed to sensing device104. This configuration allows instructions to originate anywhere the caregiver is located.

Embodiments include using one transmitter106per patient10and linking multiple sensing devices104to the single transmitter106. A second sensing device122can be implanted in the patient10. The second sensing device122takes second sensor data124and can include any or all of the features described above for sensing device102. In a further embodiment, second sensing device can include a unique second sensing device ID. Unique second sensing device ID can be used as above, to identify second sensing device and to encode or encrypt second sensor data124.

A second link126between the second sensing device122and the transmitter106can be formed similarly to first link110. Transmitter106can receive both sensor data104and second sensor data124. In an embodiment, the transmitter106can be programmed to combine the sensor data104,124into a single sensor data file to be transmitted to receiver112or can keep the sensor data104and the second sensor data124separate. To assist in differentiating between the two sensor data, the unique sensing device ID and the unique second sensing device ID can be used to encode and separate the data.

A further embodiment includes using multiple transmitters with one receiver112. Typically, a second transmitter128is linked to a second sensing device122implanted in a second patient20. However, multiple transmitters can be used with the same patient10, if the positioning of the sensing devices102or receiver112dictates. As above, second sensing device122takes second sensor data124and transmits it to second transmitter128via second link126. Second transmitter128can include a unique second transmitter ID identifying it. Receiver112can receive sensor data104and second sensor data124from the transmitter106and the second transmitter128, respectively. In an embodiment, the sensor data104,124can be encoded or encrypted using the unique transmitter and second transmitter IDs. Furthermore, if multiple sensing devices are attached to each transmitter, the sensor data can be encoded with both the unique sensing device ID and the unique transmitter ID.

Receiver112can also have a unique receiver ID to identify the receiver to the central server114and the sensor data104can be encoded/encrypted with the unique receiver ID as outlined above regarding the other unique IDs.

FIG. 2illustrates a method of monitoring a patient sensor. Sensor data104can be acquired from sensing device102implanted in the patient (step200) and linked to the transmitter106either continuously, at an interval, a burst, or upon command (step202). The transmitter106is powered internally (step204) and located external to the patient10(step206). Typically, transmitter106is in a powered down condition (step207). The transmitter106is powered up and then transmits the sensor data from the transmitter106to receiver112(step208) and the receiver112is disposed remote from the transmitter106(step210). The sensor data104is communicated from the receiver112to the central server114(step212) and central server114can store, analyze, or display the sensor data104(step214). In an alternate embodiment, the receiver112can store, analyze and display the sensor data104for an individual patient.

Embodiments include, identifying the sensing device102with a unique sensing device ID (step216) and optionally encoding the sensor data104with the unique sensing device ID (Step218). Further embodiments include powering the sensing device102from the transmitter106using a power link (step220) by optionally, transmitting energy over a wire from the transmitter106to the sensing device102(step222) or inducing energy through induction coils in the transmitter106and the sensing device102(step224). Another embodiment is temporarily storing the sensor data102in a first memory116prior to the transmitting step (step226) and erasing and/or overwriting the sensor data after the transmitting step (step228).

Referring toFIG. 3, the method can further include sending a confirmation signal acknowledging receipt of the sensor data104(step230) and issuing an alarm upon failure to receive the confirmation signal (step232). Additionally, the transmitter106can receive the confirmation signal (step234) and erase the first memory116storing the sensor data104upon receipt of the confirmation signal (step236).

Returning toFIG. 2, the transmitter106can provide an instruction to the sensing device (step238). Also, the receiver can optionally, store the sensor data104(step240), analyze the sensor data104(step242) or display the sensor data104(step244). Further, the communicating step above can include communicating the analyzed sensor data104to the central server114(step246). Also, the transmitter106can be identified with a unique transmitter ID (step248). In an alternate embodiment, transmitter106can compress sensor data104(step250) and receiver112can decompress the data (step252). Alternately, central server114can decompress the sensor data.

Turning toFIG. 4, another embodiment of the present method is illustrated. The method of monitoring a patent sensor includes acquiring sensor data104from a sensing device102disposed on the patient10(step300). Typically sensor data104is acquired continuously, but can also be taken at intervals. The sensor data can be linked to a transmitter by the first communication link110(step302). The transmitter is powered internally (step304) by power supply108and is typically located on patient10(step306). The sensor data can be accumulated over a first period of time (step308). The first period of time can be a few seconds to a few minutes and, in one embodiment, is a one minute interval. Transmitter106is powered-up and transmits the sensor data104from the transmitter106to receiver112over a second period of time (step310). The second period of time is shorter than the first period of time and is typically a factor of shorter. Once the transmission is complete, transmitter106is powered down (step312). A further step is displaying the sensor data at the receiver in pseudo real-time (step314). The display is shifted by a sum of the first and the second period of time. For example, if the sensor data is accumulated over 1 minute and the burst transmission is 6 seconds, the displayed data is time shifted (or lagged) 66 seconds from real-time.

In a further embodiment, the sensor data can be compressed prior to transmitting the sensor data104(step316) and then it can be decompressed prior to the displaying the sensor data104(step318). Compressing the sensor data104can assist in shorting the second period of time and thus shortening the burst period and the lag time. The compression compresses the waveform of the sensor data and the decompression returns the waveform of the sensor data back to its original data.

Further, it is know in the art that any analogue signals can be converted to digital signals before transmission and converted back to analogue signals, if necessary, for display and analysis.