Patient Monitoring Method and Monitoring Device

Abstract

A method of monitoring a patient includes measuring neural respiratory drive using a monitoring device ( 10 ), repeating the measurement either continuously or at regular time intervals, and comparing the measurements obtained in order to predict treatment failure and/clinical deterioration and/or re-admission. In embodiments of the invention, the neural respiratory drive is measured by obtaining a measure of the second intercostal space parasternal electromyogram. A monitoring device ( 10 ) includes a signal input ( 20 ), a processing unit ( 30 ), and a output unit ( 50 ), and is arranged to measure the neural respiratory drive, store the measured value and compare it to a previously measured value for the neural respiratory drive.

What is claimed is: 
     
         1 . A method of monitoring a patient, including:
 measuring neural respiratory drive using a monitoring device;   repeating the measurement continuously and/or at regular time intervals; and   comparing the measurements obtained in order to predict treatment failure and/or clinical deterioration and/or admission from home or re-admission to hospital.   
     
     
         2 . A method as claimed in  claim 1 , wherein the neural respiratory drive is measured by obtaining a measure of the second intercostal space parasternal electromyogram. 
     
     
         3 . A method as claimed in  claim 1 , including obtaining a value for the neural respiratory drive time index by multiplying the value of the neural respiratory drive time product by the respiratory rate. 
     
     
         4 . A method as claimed in  claim 1 , including:
 1) obtaining a value for a normalized neural respiratory drive (which may be calculated as EMG para /EMG paramax  and termed EMG para%max );   2) obtaining the respiratory rate of the patient, expressed as breaths per minute (RR/min);   3) obtaining a value for the neural respiratory drive index by multiplying the value of the neural respiratory drive obtained in Step 1 by the respiratory rate (EMG para%max .RR);   4) repeating Steps 1 to 3 continuously and/or after a first given period of time and comparing the two neural respiratory drive index values obtained.   
     
     
         5 . A method as claimed in  claim 4 , wherein Steps 1 to 3 are carried out upon admission into hospital and repeated just prior to discharge from hospital. 
     
     
         6 . A method as claimed in  claim 1 , including:
 1) obtaining a value for a normalized neural respiratory drive by:   a) carrying out parasternal electromyography to obtain a raw signal during normal breathing;   identifying and obtaining the root mean square of the raw signal to obtain a rectified trace;   identifying and obtaining the peak magnitude of the rectified trace for each inspiration;   calculating the mean of the peak magnitudes identified (EMG parapeak );   b) carrying out parasternal electromyography to obtain a raw signal during at least two (or preferably at least three) sniff maximal maneuvers;   obtaining the root mean square of the raw signal to obtain a rectified trace;   identifying and selecting the peak magnitude of the rectified trace (EMG paramaxpeak );   c) expressing the mean of the peak calculated in Step la as a percentage of the peak magnitude selected in Step 1b (EMG para%maxpeak )   2) obtaining the respiratory rate of the patient, expressed as breaths per minute;   3) obtaining a value for the neural respiratory drive index by multiplying the value of the EMG para%maxpeak  (NRD) obtained in Step 1c by the respiratory rate;   4) repeating Steps 1 to 3 continuously and/or after a first given period of time and comparing the two neural respiratory drive index values obtained.   
     
     
         7 . A method as claimed in  claim 1 , including:
 obtaining a value for the neural respiratory drive time product by carrying out parasternal electromyography to obtain a raw signal during normal breathing;   obtaining the root mean square of the raw signal to obtain a rectified trace;   measuring the area under the rectified trace;   obtaining a value for the neural respiratory drive time product index by multiplying the neural respiratory drive time product by the respiratory rate; and   comparing the two neural respiratory drive time index values obtained.   
     
     
         8 . A method as claimed in  claim 7 , including:
 identifying and obtaining the area under the curve of the rectified root mean square of the raw signal;   calculating the mean of the area under the curves identified (EMG paraAUC );   identifying and selecting the area under the curve of the rectified trace (EMG paramaxAUC );   expressing the mean area under the curve as a percentage of the maximum area under the curve (EMG para%maxAUC ); and   obtaining neural respiratory drive time index by multiplying the value of the EMG para%maxAUC  (NRDTP) by the respiratory rate.   
     
     
         9 . A method as claimed in  claim 1 , wherein the patient has respiratory disease, for example, wherein the respiratory disease is:
 (1) an acute exacerbation of chronic obstructive pulmonary disease;   (2) an acute exacerbation of chronic respiratory disease;   (3) acute respiratory failure;   (4) chronic respiratory disease;   (5) chronic respiratory failure;   (6) acute exacerbation of chronic heart failure;   (7) acute heart failure; or   (8) chronic heart failure.   
     
     
         10 . A method as claimed in  claim 6 , wherein the peak magnitude is obtained for each inspiration over a time period of approximately 30 seconds to 3 minutes. 
     
     
         11 . A monitoring device including: a signal input, and a processing unit, the monitoring device being arranged to:
 (1) receive a first raw parasternal electromyography signal at the signal input;
 execute computer program code in the processing unit to: 
   (2) determine the root mean square of the raw parasternal signal to obtain a rectified trace;   (3) identify the peak magnitude of the rectified parasternal trace for each inspiration over a second given period of time;   (4) calculate the mean of the peak magnitudes identified;   (5) receive further and determine raw parasternal electromyography signals during at least two (preferably at least three) sniff maneouvres;   (6) determine the root mean square of the raw signal to obtain a further rectified trace;   (7) determine the peak magnitude of the further rectified trace;   (8) express the mean of the first peak magnitude as a percentage of the peak magnitude of the further rectified trace obtained during the sniff manouevre;   (9) receive data on the respiratory rate of the patient, expressed as breaths per minute;   (10) determine a value for the neural respiratory drive index by multiplying the value of the neural respiratory drive by the respiratory rate; and   (11) store the measured/determined values of the neural respiratory drive a data repository.   
     
     
         12 . A monitoring device as claimed in  claim 11 , being arranged to determine a subsequent neural respiratory drive index and compare with the stored value. 
     
     
         13 . A monitoring device as claimed in  claim 11 , operable to identify the area under the curve of the rectified root mean square of the raw parasternal signal for each inspiration over a second given period of time to display the measured/determined neural respiratory drive values in real time; to calculate the mean of the area under the curves identified; and to determine the values for NRDTP and NRDTI from the area under the curve of the rectified trace. 
     
     
         14 . A method as claimed in  claim 1 , including carrying out substantially real time processing of biological signals received from surface electrodes, and converting them into a physiological biomarker by processing the signals from the electrodes to obtain and display heart rate (HR), respiratory rate (RR), neural respiratory drive (NRD), neural respiratory drive index (NRDI). 
     
     
         15 . A method as claimed in  claim 14 , including obtaining and displaying neural respiratory drive time product (NRDTP) and neural respiratory drive time index (NRDTI). 
     
     
         16 . A method as claimed in  claim 14 , wherein neural respiratory drive (NRD) is determined from the electromyogram of the 2nd intercostal parasternal muscles (EMG para ) by using electrodes and amplifiers, and processing the para, signals using analog to digital conversion followed by digital filtering and arithmetic conversion of the signal. 
     
     
         17 . A method as claimed in  claim 1 , wherein signals are recorded during resting breathing to provide an indication of a patient's current respiratory effort determined by objectively measuring EMG para  activity, and wherein the patient performs repeated maximum sniff manoeuvres in order to allow the signal to be normalised for an individual patient maximum effort (EMG para%max ). 
     
     
         18 . A method as claimed in  claim 1 , including the following steps:
 1) identifying patients at potential risk of deterioration;   2) placing surface electrodes over the parasternal muscles of the second intercostal space along with a reference electrode over the electrically neutral clavicle;   3) amplifying electrical signals from the two recording electrodes;   4) passing the amplified signal to an analog to digital converter to allow for further computer processing; and   5) integrating the signals to produce the essential biological variables for clinical interpretation.   
     
     
         19 . A method as claimed in  claim 14 , wherein the signal is amplified to a factor of 1000 and analog filtered at 10 Hz and 2000 Hz to remove contributions from other muscle activity and maximize signal from the parasternal muscles. 
     
     
         20 . A method as claimed in  claim 1 , including at least one of the following features:
 Signal quality assessment (including initial signal)   ECG (QRS) detection and HR calculation   ECG artifact accommodation or removal from EMG para  signal   Calculation of RMS   EMG para  analysis including peak-peak analysis to calculate respiratory rate, peak value to calculate EMG para%maxpeak  and multiplication by respiratory rate to calculate NRDI   EMG para  analysis to calculate area under the curve of the signal to calculate EMG para%maxAUC  by normalizing for the EMG paramaxAUC  and multiplying by respiratory rate to calculate NRDTI.