Monitoring pressure in a body cavity

Abstract

The present invention relates to an apparatus for monitoring, sampling and storing pressure in a body cavity or blood pressure of a patient. The apparatus is a small portable recording unit for pressure assessment, including software for analysis of pressure recordings. A pressure transducer implanted e.g. in the skull of a patient senses the pressure and outputs a signal indicative of the pressure in the patients skull. The signals indicative of the pressure are converted to digital signals and sampled and stored by the microcomputer. The apparatus is sufficiently small to allow the patient to move freely around and not be bedridden during pressure recording. Intracranial pressure is sampled and stored by the apparatus several times a second for several days. After the end of pressure sampling, the data is transferred to a computer or network station for analysis. The invention includes a new method for analysis of pressure as well as software for performing the analysis. The computer software provides different quantitative presentations of pressure curves as a matrix of the number of intracranial pressure elevations of different levels or durations, a matrix of pressure changes of different levels and durations, or a matrix of the number of single pulse pressure waves with preselected characteristics.

1 . Method for measuring and analyzing pressure in a patient, comprising the steps of 
 applying a pressure sensor to the patient,    sampling, at selected intervals, a signal from the sensor representative of said pressure,    converting the sampled signal to digital form and storing the digital sample value along with a time reference,    analyzing the stored sample values in order to generate a presentation of at least one of the following: 
 number of pressure elevations with any selected combination of level and duration,  
 number of pressure changes with any selected combination of level difference and duration of change,  
 number of single pulse pressure waves with preselected characteristics regarding minimum, maximum, amplitude, latency and rise time.  
   
     
     
         2 . Method according to  claim 1 , wherein the step of applying a pressure sensor involves implanting the sensor in a body cavity of the patient.  
     
     
         3 . Method according to  claim 1 , wherein the step of applying a pressure sensor involves applying a non-invasive technique with a sensor using acoustic measuring signals.  
     
     
         4 . Method according to  claim 1 , wherein the step of applying a pressure sensor involves applying a sensor for measuring blood pressure.  
     
     
         5 . Method according to  claim 1 , wherein the measurements are made while the patient is free to move about.  
     
     
         6 . Method according to  claim 1 , wherein the presentation generated is in the form of absolute numbers, percentages or numbers per time unit.  
     
     
         7 . Method according to  claim 1 , wherein the sampling rate is at least 10 Hz, and the measurements are taken over a period of at least 24 hours.  
     
     
         8 . Method according to  claim 7 , wherein the sampling rate is at least 100 Hz.  
     
     
         9 . Method according to  claim 7 , wherein the sampling rate is at least 150 Hz.  
     
     
         10 . Method according to  claim 7 , wherein the measurements are taken over a period of at least 48 hours.  
     
     
         11 . Apparatus for recording and storing pressure recordings from a pressure sensor applied to a patient, comprising 
 a first connector for connecting the apparatus to a pressure sensor,    an analog-to-digital converter for converting received pressure measurements to digital form,    processing means in communication with the analog-to-digital converter, capable of reading out samples of the digitally converted pressure measurements and storing said measurements in a data memory connected to said processing means,    input/output interface in communication with the processing means and connected to a second connector for connecting the apparatus to external computing means, and    a power source for supplying the apparatus with power.    
     
     
         12 . Apparatus according to  claim 11 , further comprising a galvanic circuit connected to the first connector for preventing the transfer of electrical energy from the apparatus towards the sensor.  
     
     
         13 . Apparatus according to  claim 11 , further comprising a signal conditioner for removing noise from the received pressure measurement signals.  
     
     
         14 . Apparatus according to  claim 13 , wherein said signal conditioner is an analog filter connected between the first connector and the analog-to-digital converter.  
     
     
         15 . Apparatus according to  claim 13 , wherein said signal conditioner is a digital filter connected to the output of the analog-to-digital converter.  
     
     
         16 . Apparatus according to  claim 11 , further comprising an input control for entering control and calibration signals.  
     
     
         17 . Apparatus according to  claim 11 , further comprising a display connected to said processing means.  
     
     
         18 . Apparatus according to  claim 11 , wherein said data memory further contains instructions controlling the operation of the processing means.  
     
     
         19 . Apparatus according to  claim 11 , further comprising an alarm circuit capable of generating an audible or visual alarm upon detection of low memory capacity in the data memory or low power capacity in the power source.  
     
     
         20 . Apparatus according to  claim 11 , wherein said data memory is a random access memory (RAM) circuit.  
     
     
         21 . Apparatus according to  claim 11 , wherein said data memory is a magnetic storage device.  
     
     
         22 . Apparatus according to  claim 11 , wherein the processor and the analog-to-digital converter in combination are capable of sampling the received pressure measurements with a sampling rate of at least 10 Hz.  
     
     
         23 . Apparatus according to  claim 22 , wherein the sampling rate is at least 100 Hz.  
     
     
         24 . Apparatus according to  claim 22 , wherein the sampling rate is at least 150 Hz.  
     
     
         25 . Apparatus according to  claim 11 , wherein the processor is programmable through input control means to operate with a sampling rate between a minimum sampling rate and a maximum sampling rate.  
     
     
         26 . Apparatus according to  claim 11 , wherein said data memory has a capacity which allows the storage of at least 24 hours of continuous sampling of the received pressure measurements at maximum sampling rate.  
     
     
         27 . Apparatus according to  claim 11 , wherein said data memory has a capacity which allows the storage of at least 48 hours of continuous sampling of the received pressure measurements at maximum sampling rate.  
     
     
         28 . Apparatus according to  claim 11 , comprising a plurality of input connectors and means for multiplexing pressure signals from said input connectors for the simultaneous recording of pressure signals from more than one pressure sensors.  
     
     
         29 . System for the analysis of recorded pressure data, comprising 
 communication interface for receiving a set of digital pressure sample values;    data memory for storing the received sample values;    processing means with access to said data memory, capable of analyzing said sample values in order to determine at least one of the following: 
 number of pressure elevations with any selected combination of level and duration,  
 number of pressure changes with any selected combination of level difference and duration of change,  
 number of single pulse pressure waves with preselected characteristics regarding minimum, maximum, amplitude, latency and rise time;  
   video interface in communication with said processing means and capable of, in combination with the processor means, generating a visual presentation of the result of any analysis performed on the pressure sample values together with a graphical user interface;    a display for displaying the generated visual presentation; and    input means allowing a user of the system to enter and change parameters on which said analysis should be based.    
     
     
         30 . System according to  claim 29 , wherein said parameters include at least some of the following: 
 pressure intervals defining a number of pressure elevations, pressure change intervals defining a number of pressure change step sizes, time intervals defining a number of durations, pressure wave characteristics including minimum, maximum, amplitude and latency, selection of type of analysis, and selection of presentation of numbers as absolute numbers, percentages or numbers per time unit.    
     
     
         31 . Computer program product for controlling a computer on which is stored a set of values representing pressure samples with a time reference, comprising program instructions for causing the computer to perform the steps of 
 receiving from a user interface or as pre stored default values a set of parameters on which an analysis of said set of samples should be based;    analyzing said sample values in order to determine at least one of the following: 
 number of pressure elevations with any selected combination of level and duration,  
 number of pressure changes with any selected combination of level difference and duration of change,  
 number of single pulse pressure waves with pre-selected characteristics regarding minimum, maximum, amplitude, latency and rise time;  
   generating a visual presentation of said analysis.    
     
     
         32 . Computer program product according to  claim 31 , stored on a computer readable medium.  
     
     
         33 . Computer program product according to  claim 31 , carried on a propagated signal.