Surgery – Diagnostic testing – Measuring fluid pressure in body
Reexamination Certificate
2000-03-24
2002-07-09
Shaver, Kevin (Department: 3736)
Surgery
Diagnostic testing
Measuring fluid pressure in body
C600S586000
Reexamination Certificate
active
06416483
ABSTRACT:
RELATED APPLICATIONS
A related patent application by M. E. Halleck and M. D. Halleck has been filed concurrently with this patent application entitled “Apparatus and Method for Detecting Very Low Frequency Acoustic Signals” (Attorney Docket No. ILIF01-00036). A related patent application by M. E. Halleck, M. D. Halleck, M. L. Lehrman and A. R. Owen has been filed concurrently with this patent application entitled “Physiological Condition Monitors Utilizing Very Low Frequency Acoustic Signals” (Attorney Docket No. ILIF01-00053). A related patent application by M. E. Halleck and M. D. Halleck has been filed concurrently with this patent application entitled “System and Method for Remotely Monitoring At Least One Physiological Characteristic of a Child” (Attorney Docket No. 34). Another related patent application by M. E. Halleck, M. D. Halleck and G. V. Halleck has been filed concurrently with this patent application entitled “System and Method for Seizing a Communication Channel in a Commercially Available Child Monitor” (Attorney Docket No. ILIF01-00054).
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to a sensor and a method for detecting very low frequency acoustic signals. The sensor of the present invention comprises a chamber and a microphone for detecting very low frequency acoustic signals in the frequency range of one tenth Hertz (0.1 Hz) to thirty Hertz (30.0 Hz).
BACKGROUND OF THE INVENTION
Microphones in physiological condition monitors are used to detect sounds that are indicative of physiological processes. Physiological condition monitors are capable of obtaining and recording signals indicative of a person's physiological processes. The most commonly monitored physiological processes are respiration and cardiac activity. Physiological condition monitors that monitor respiration and cardiac activity usually comprise one or more sensors coupled to the body of the person whose physiological conditions are to be measured. The sensors are capable of sensing changes in physical parameters that are caused by the person's respiration and cardiac activity. Physiological condition monitors measure and record waveform signals received from the sensors. Electrocardiogram (ECG) waveform signals are the most commonly used waveforms for measuring a person's cardiac activity. Respiration waveform signals may be electronically derived using techniques such as impedance pneumography or inductive plethysmography. Respiration waveform signals are used to measure a person's breathing rate and other types of information concerning respiration.
The present invention comprises a chamber and a microphone that is capable of detecting very low frequency acoustic signals. The present invention is particularly useful in that it may be used to detect and monitor physiological conditions. For purposes of illustration, the present invention will be described with reference to physiological condition monitors that are capable of monitoring respiration and cardiac activity. It is understood however, that the present invention is not limited to use in respiration monitors, and is not limited to use in cardiac activity monitors, and is not limited to use in physiological condition monitors in general. The present invention may be used to detect any type of very low frequency acoustic signal.
Low heart rate is referred to as bradycardia. High heart rate is referred to as tachycardia. Cessation of respiration is referred to as apnea. When a person exhibits apnea, bradycardia or tachycardia a life threatening condition very likely exists. Physiological condition monitors that are capable of continuously monitoring a person's respiration and cardiac activity are extremely useful for quickly detecting apnea, bradycardia or tachycardia. Such physiological condition monitors are also useful for quickly detecting other abnormal conditions such as a very slow breathing rate or a very high breathing rate.
Infants who are susceptible to sudden infant death syndrome are known to exhibit apnea and bradycardia. Physiological condition monitors that are capable of continually monitoring respiration and cardiac activity are particularly useful in the early detection of apnea or bradycardia in infants. Most physiological condition monitors are equipped with an alarm system to sound an alert when such conditions are detected.
A physiological condition monitor may be coupled directly to a person who is a patient in a hospital bed. In such an arrangement the waveform signals from the sensors coupled to the patient's body may be sent through wires directly to a detector circuit (and other circuitry) located in a console by the patient's bed. The wires attached to the patient restrict the patient's movements and frequently become tangled as the patient moves. The tangling of the wires can also result in the sensors becoming detached from the patient. The loss of sensor contact can set off an alarm signal.
In other cases it is more practical to provide one or more sensors located in a belt, harness or item of clothing that is to be worn by the person to be monitored. In this type of physiological condition monitor the waveform signal information from the sensors is transmitted via a radio frequency transmitter to a radio frequency receiver in a base station unit that is located away from the site of the physiological condition sensors. The base station unit contains circuitry for analyzing and recording the waveform signal information. The base station unit contains circuitry for detecting abnormal conditions in the person's breathing (such as apnea) or abnormal conditions in the person's cardiac activity (such as bradycardia or tachycardia). Because of the freedom of movement that this type of monitor provides, it is the preferred type of monitor for monitoring the physiological conditions of infants.
If the data that is acquired by the physiological condition monitor is not transmitted to the base station unit and recorded there, then the data may be recorded in a memory data storage device located within the physiological condition monitor. To preserve the freedom of movement that is provided by a monitor that is worn on a belt, harness or item of clothing, the memory data storage device within the physiological condition monitor must be battery powered.
Electrocardiogram (ECG) waveform signals are commonly used to obtain information concerning a person's cardiac activity. To obtain ECG waveforms an ECG sensor unit is coupled to the person whose cardiac activity is to be measured. The ECG sensor unit is coupled to the person via electrodes capable of receiving signals that are representative of cardiac activity directly from the person's body. In such an arrangement the electrodes must be attached directly to the person's skin in order to receive the signals. The ECG sensor unit receives the ECG electrical signals from the electrodes. The ECG signals received by the ECG sensor unit are then either recorded within the physiological condition monitor or transmitted to a base station unit.
It is possible to obtain information about cardiac activity from acoustic signals. For example, U.S. Pat. No. 4,306,567 to Krasner discloses a sensor apparatus coupled directly to the skin of a person. The Krasner sensor apparatus is capable of detecting acoustic signals from cardiac contractions within a frequency bandwidth between about thirty Hertz (30.0 Hz) and ninety Hertz (90.0 Hz) . The acoustical energy associated with the cardiac contractions detected by the Krasner sensor apparatus exhibits a maximum signal-to-noise ratio at about forty five Hertz (45.0 Hz).
The Krasner sensor apparatus is also capable of detecting acoustic signals from breathing activity (i.e., respiration) within a frequency bandwidth between about three hundred Hertz (300.0 Hz) and six hundred Hertz (600.0 Hz) . The acoustical energy associated with the breathing activity detected by the Krasner sensor exhibits a maximum signal-to-noise ratio at about four hundred Hertz
Halleck Michael D.
Halleck Michael E.
Lehrman Michael L.
iLife Systems, Inc.
Shaver Kevin
Wingood Pamela
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