This invention relates to emergency medical alert devices and, in particular, to a system including a body worn audio communication device which can provide bystanders with verbal instructions in the event of a catastrophic personal health emergency.
Medical alert devices can save a person's life when the person experiences a catastrophic medical condition in a public area. These devices are of particular use in situations that leave a patient unconscious, such as the onset of sudden cardiac arrest. These devices can respond by communicating with a system that provides it with an indication of personal health, which can be as basic as “ok” or “not ok”. This indication may be manually activated, or may include automated monitoring of one or more patient attributes coupled with automated determination of the patient's state of health.
Personal emergency response devices are manually activated systems that summon aid, which can include voice or other locally generated audio instructions that would help bystanders provide emergency assistance. One such device is described in U.S. Pat. No. 6,292,687 and includes a heart dysfunction reader and sensor worn by a patient on the chest or wrist. A vital sign is monitored and the sensor determines whether a sign indicates a heart dysfunction. A signal is sent to a loop process which in turn sends a signal to a personal alarm worn by the patient. The personal alarm can broadcast a synthetic or recorded voice alerting bystanders to the medical condition.
Another device is described in US Pat. Appl. 2005/0065445 which describes an implantable sensor that, upon detection of abnormal heart activity, transmits a radio frequency signal to an external receiver carried by the patient. The external receiver has multiple communication capabilities including an enunciator which may be heard by bystanders.
Another device is an attitude-activated warning device described in U.S. Pat. No. 3,634,885. The device is worn by the patient and contains a mercury switch when closes if the patient collapses to a prone position. The switch closure activates an endless tape in the device which gives instructions to bystanders by means of a loudspeaker. A similar device is described in U.S. Pat. No. 6,570,503. See also US Pat. Appl. 2005/0030190.
There remains a need for a body worn audio communication device which monitors a patient vital sign and issues verbal instructions to bystanders in the event of an incapacitating medical emergency. Such a device should be compact, unobtrusive, and exhibit low power consumption.
In accordance with the principles of the present invention, an audio communication device is described which improves the probability of a patient's survival by providing directions for bystanders in verbal form from a physiological sensor and processor worn on the patient's body. The simple sounding of an alarm tone might cause a bystander to pay attention to an unconscious person, but when the alarm is accompanied by a voice prompt that for example, states “This is a medical emergency. Please call for help immediately”, the bystander will know that the alarm was not a cell phone ringing, but was in fact a call for assistance. Upon hearing the voice instruction, the bystander will be able to recognize the nature of the alarm and is given the next steps to follow, thus reducing overall reaction time and improving patient outcome.
In the drawings:
a illustrates in block diagram form the power subsystem for the medical audio communication system of
a illustrates a push-pull amplifier portion of the audio drive circuitry of the system of
b illustrates an H-bridge amplifier portion of the audio drive circuitry of the system of
There are numerous ways to implement an on-body emergency instruction system in accordance with the principles of the present invention. In one example described below the system comprises a device that integrates a physiological signal sensor, processor, and loudspeaker that attaches to the skin and that is unobtrusive such that a wearer is not overly burdened by its presence. Conventional audio transducers for example, tend to be relatively large and bulky if they are to be loud enough to be heard by bystanders. Headphone drivers, for example, are small but may not produce sufficient audio volume to be easily heard at a short distance. Speaker systems consisting of a motor and a moving diaphragm tend to be large, bulky, and require considerable power. These characteristics all conflict with the objective of being unobtrusive.
The following examples of the present invention provide satisfactory fidelity while emphasizing small size and power efficiency. These examples take advantage of the ability to communicate spoken information by modulation of a pulse train. One technique is to drive a piezoelectric transducer at a very low frequency, well below its natural or designed resonant frequency. One of the following examples drives the transducer by modulating the transducer's supply voltage with the envelope of the spoken words. Doing so causes the amplitude of the transducer's output to track the verbal amplitude, giving an understandable representation of the spoken message. In addition, because of a typical “cut-off” characteristic wherein the transducer will produce no sound if the supply voltage fall below a certain threshold, some frequency content can be reproduced as well. To maximize the volume of the resulting speech, the source material should be optimized in frequency content, preferably near the transducer's resonant frequency. Likewise, speech intelligibility can be optimized by altering the pace and intonations in the source material. Piezoelectric transducers that are, for instance, 2 mm thick and 6 mm square can produce sound pressure levels in excess of 85 dB while consuming only about 20 mA of current. These levels are easily heard by bystanders. The small size permits inclusion of this piezoelectric “loudspeaker” in small, light packages that can be integrated into a body-worn monitoring system, and the inherent design of the piezoelectric transducer produces high audio volume with minimal power demand.
In another example, a frequency modulation technique is employed. Turning to
a illustrates a power subsystem which can be used to power the components of the system of
Number | Date | Country | Kind |
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PCT/IB06/51899 | Jun 2006 | IB | international |
This application claims the benefit of U.S. provisional application Ser. No. 60/693,645 filed Jun. 24, 2005.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IB06/51899 | 6/13/2006 | WO | 00 | 12/14/2007 |
Number | Date | Country | |
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60693645 | Jun 2005 | US | |
60748917 | Dec 2005 | US |