Abstract:
A patient in intensive care is monitored by connecting the outputs of a plurality of sensors to a computer, where the sensors all relate to one mode of functioning such as heart beating, respiration, infusion of a liquid into the patient, etc. The sensor outputs are delivered to a computer that sounds an alarm, only if all sensors that indicate one function (e.g. heart beating) indicate dangerously low operation of that function. This avoids many false alarms caused by one sensor having a low output such as due to accidental disconnection of a wire.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    False sound alarms are one of the greatest annoyances in critical care settings, such as an ICU (intensive care unit) environment. In fact, more than 97% of sound alarms are false positive alarms. Sometimes caregivers disable the alarms, which can result in preventable fatal events. A system that minimized false alarms while sounding legitimate alarms, would be of value. 
       SUMMARY OF THE INVENTION 
       [0002]    The present invention provides apparatus and methods for reducing and prioritizing alarms based on sensors that sense cardiovascular patterns, respiratory patterns, electrocardiogram patterns, pulse rate and pulse strength, oxygen saturation such as is sensed by a pulse oximeter, and arterial pressure. Sensors can include those that sense central venous pressure, pulse morphology as well as arterial pressure wave forms, end tital PCO 2  (partial pressure of CO 2 ), operation of a ventilator, and operation of an infusion pump. By providing a plurality of sensors that each indicates one function, the failure of one sensor can be overridden by the outputs of other sensor(s). 
         [0003]    The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is view of a patient in an ICU environment, with sensors that sense functioning related to beating of a patient&#39;s heart. 
           [0005]      FIG. 2  is a view similar to that of  FIG. 1 , with sensors related to infusion. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0006]      FIG. 1  shows a patient P in an intensive care environment  10 , wherein the patient is coupled to several sensors that monitor the functioning of various systems of the patient&#39;s body. These sensors include heart function sensors comprising a patient heart sensor  20  whose output  22  includes electrical pulses  24  of measurable height  26  and measurable spacing  28 . The output of the sensor is delivered to a first input  31  of a computer  30  which measures the height and spacing of the heart pulses. If the pulse height  26  is below a selected height or the spacing  28  has increased to more than a predetermined spacing then the computer generates a failure signal on an output  32 . Another sensor  40  senses the blood pressure, indicated at  41 , of the patient. A signal representing the blood pressure is delivered to computer input  42 . If the signal  41  indicates failure (e.g. the difference, between systolic and diastolic pressure is less than a certain minimum), a blood pressure signal output  34  is delivered. The outputs  32 ,  34  delivered to part  36  of the computer results in sound alarm signal  38  only if all outputs  32 ,  42  indicate failure of patient heart functioning. 
         [0007]    Another sensor  50  senses the oxygen saturation of the patient&#39;s blood and delivers a signal to computer input  51 . Still another sensor  52  senses the PCO 2  (partial pressure of carbon dioxide) in the patient&#39;s blood and delivers a corresponding signal to computer input  53 . A pulse oximeter can be used to sense PCO 2 . If the output  51  of the sensor  50  shows at least a limited level of oxygen in the patient&#39;s blood, then this means that the heart is beating to circulate the blood through the lungs to pick up oxygen. If the output  53  of sensor  52  shows at least a predetermined minimum of carbon dioxide then this indicates that the patient&#39;s blood is circulating. The computer will not generate an emergency sound alarm so long as one of the sensors  20 ,  40 ,  50 ,  52  indicates that the patient&#39;s heart is beating regularly, or at least does not indicate failure. 
         [0008]    If the patient&#39;s heart is not beating regularly, then this is a critical failure that should be rectified immediately. If the output  22  of sensor  20  shows a pulse spacing  28  greater than a predetermined limit such as less than one pulse per three second, or shows a pulse height  26  less than one-fourth of the average previous height when a nurse determined that the heart was beating appropriately, then this indicates a critical failure that should be rectified immediately. However, if the output of the blood pressure sensor  40  or the output of sensor  50  or  52  is more than a minimal level, then this indicates that the heart is beating properly, or at least is beating sufficiently that this is not a critical situation. Actually, an improper output of only one sensor such as sensor  20 . indicates that one of the wires that connects to the heart rate sensor  20  has been disconnected or is not connected in a low resistance connection. Functioning of the other sensors  50 ,  52  indicate that the heart is beating. When the computer senses a bad output, or failure from one sensor but other sensors indicate otherwise, then the computer  30  generates a visual indication such as at  70  that the heart rate sensor  20  or the blood pressure sensor  40  or other sensors such as  50  or  52  indicate improper heart functioning then lights at  72 ,  74  light up. It is easier for a nurse to check these sensors which cause a light  70 ,  72  etc. to light up when he/she has time, than to treat a poor sensor output as an emergency that requires he/she to drop everything to concentrate on the emergency. 
         [0009]    Another function that is commonly monitored in an ICU is patient respiration. Sensors that indicate breathing include a chest vertical expansion-contraction sensor  100 , an air flow sensor  102 , an oxygen saturation sensor  104  and a PCO 2  sensor  106 . If any of these respiration sensors indicate respiration, then no alarm will be sounded, although a visual indication will be generated that the sensor is not functioning properly. 
         [0010]    Another function that is commonly monitored in an ICU is proper operation of an infusion pump that infuses one to several different fluids, including a saline solution, an antimicrobial fluid, etc. For those infusions that are critical, applicant can provide sensors including a sensor  110  ( FIG. 2 ) that detects the level of fluid in a container  112  from which the fluid in introduced into the patient. The computer  30  sounds an alarm if the level does not decrease as expected, from the initial level existing when a nurse first connected the fluid container to the infusion pump, and other sensor(s) also indicate improper infusion. Sensor  114  senses movement of liquid in an infusion tube. Sensor  116  senses the pressure of air in the infusion tube. 
         [0011]    The visual indicators preferably indicate different levels of importance. In one example, a particular one of a plurality of sensors does not agree with the other sensors for a critical function such as heart rate, breathing, infusion, and that sensor seldom malfunctions. Then, the visual indicator  70  may be a light that flashes on and off . Other visual indicators may include the continuous display of a color such as from a steady light. 
         [0012]    Thus, the invention provides a system for generating alarms, where the system includes a plurality of sensors that sense functioning that indicates the same general condition such as heart beating, respiration, or infusion. The system generates a sound alarm indicating that a caregiver&#39;s attention is required immediately, only if all sensors indicate a patient malfunction for the particular condition. If one or more sensors indicate proper functioning, or at least temporarily acceptable functioning, then a visual indicator is operated, but a sound alarm is not sounded. 
         [0013]    Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.