Devices and methods for respiratory variation monitoring by measurement of respiratory volumes, motion and variability

Abstract

This invention is directed to devices and methods for assessing a patient. The devices have at least one impedance measuring element functionally connected to a programmable element, programmed to analyze an impedance measurement, and to provide an assessment of at least one respiratory parameter of the patient. Preferably the device includes electronics which aid in calibration, signal acquisition, conditioning, and filtering.

1 . A method for assessing a patient, comprising:
 acquiring a physiological signal from a patient functionally connected to a programmable element;   obtaining a calibration coefficient;   automatically adjusting the acquisition circuitry;   determines signal variation;   automatically adjusts for the signal variation; and   analyzing the physiological signal to provide an assessment of at least one respiratory parameter of a patient.   
     
     
         2 . The method of  claim 1 , wherein the calibration coefficient calculation is based on at least one of: bioelectrical impedance analysis of the patient, the demographic information for the patient, calculated from physiological measurements of the patient, measured ECG signals of the patient, baseline impedance levels of the patient, measurements from a spirometer, and measurements from a ventilator. 
     
     
         3 . The method of  claim 1 , wherein the at least one respiratory parameter is associated with a measurement of one or more of the patient's respiratory rate, the patient's respiratory pressure, the patient's respiratory flow, the patient's end tidal CO 2 , the patient's sublingual CO 2 , the patient's intensity of respiration, a measurement that assesses variability, variation, or complexity in at least one of the patient's respiratory rate, the patient's respiratory pressure, the patient's respiratory flow, a patient's end tidal CO 2 , the patient's sublingual CO 2 , the patient's intensity of respiration, a measurement of at least one of the shape of the patient's respiratory curve, change in the shape of the patient's respiratory curve, a respiratory curve based on the patient's inhaled volume, a respiratory curve based on the patient's exhaled volume, a respiratory curve based on the patient's inhaled pressure, a respiratory curve based on the patient's exhaled pressure, a respiratory curve based on the patient's inhaled flow, a respiratory curve based on the patient's exhaled flow, a respiratory curve based on motion of the patient's chest as measured by imaging, a respiratory curve based on motion of the patient's chest as measured by contact sensors placed on the chest, a respiratory curve based on motion of the patient's abdomen as measured by imaging, a respiratory curve based on motion of the patient's abdomen as measured by contact sensors placed on the abdomen, a respiratory curve based on motion of both the patient's chest and abdomen as measured by imaging, a respiratory curve based on motion of the patient's chest and abdomen as measured by contact sensors placed on the chest and abdomen, variation of the patient's interbreath intervals, phase lag between the patient's impedance and volume signal, variation of phase lag between the patient's impedance and volume signal, a measurement that assesses variability, variation, or complexity at least one of the shape of the patient's respiratory curve, change in the shape of the patient's respiratory curve, a respiratory curve based on the patient's inhaled volume, a respiratory curve based on the patient's exhaled volume, a respiratory curve based on the patient's inhaled pressure, a respiratory curve based on the patient's exhaled pressure, a respiratory curve based on the patient's inhaled flow, a respiratory curve based on the patient's exhaled flow, a respiratory curve based on motion of the patient's chest as measured by imaging, a respiratory curve based on motion of the patient's chest as measured by contact sensors placed on the chest, a respiratory curve based on motion of the patient's abdomen as measured by imaging, a respiratory curve based on motion of the patient's abdomen as measured by contact sensors placed on the abdomen, a respiratory curve based on motion of both the patient's chest and abdomen as measured by imaging, a respiratory curve based on motion of the patient's chest and abdomen as measured by contact sensors placed on the chest and abdomen, variation of the patient's interbreath intervals, phase lag between the subject's impedance and volume signal, variation of phase lag between the subject's impedance and volume signal, and combinations thereof. 
     
     
         4 . The method of  claim 1 , wherein the assessment of at least one physiological measurement of the patient comprises at least one measurement selected from the group consisting of a calculation or estimation of the patient's viability, of the patient's injury severity, an assessment of the patient's likelihood of collapsing, an assessment of the patient's likelihood of suffering respiratory failure, an assessment of the patient's depth of anesthesia, an assessment of the patient's drug dosage level, an assessment of the patient's likelihood of cardiopulmonary failure, an assessment of the likelihood of equipment failure for equipment associated with treating the patient, and combinations thereof. 
     
     
         5 . The method of  claim 1 , further comprising placing one or more remote probes on the thorax or abdomen of the patient and analyzing one or more remote probe data sets collected from the one or more remote probes. 
     
     
         6 . The method of  claim 5 , wherein an impedance measurement is based on a plurality of remote probe data sets, and further comprising enhancing at least one of the plurality of remote probe data sets, or stabilizing at least one of the plurality of remote probe data sets, or analyzing each of the plurality of remote probe data sets for dynamic range and signal to noise ratio (SNR) values. 
     
     
         7 . The method of  claim 1 , wherein the further analysis of the at least one respiratory parameter comprises correlating the at least one respiratory parameter with a predefined respiratory condition. 
     
     
         8 . The method of  claim 1 , wherein the assessment determines an index of respiratory sufficiency which is used as a diagnostic or monitoring tool. 
     
     
         9 . The method of  claim 1 , further comprising a patient controlled analgesia system coupled to the programmable element. 
     
     
         10 . The method of  claim 9 , wherein the programmable element, based on the assessed at least one respiratory parameters, at least one of determines the effect of one or more drugs or medical interventions on the patient, provides information supporting extubating the patient, suggests extubating the patient, provides information supporting adjusting the patient's therapies or medications, suggests adjusting the patient's therapies or medications, provides information supporting adjusting ventilator settings, suggests adjusting ventilator settings, provides information supporting adjusting weaning the patient off ventilation, suggests weaning the patient off ventilation, provides information to assesses a patients status before, during, or after surgery or medical procedure, monitors for air leaks, monitors for improper ventilation, monitors exercise, monitors stress levels, and monitors disease or medical condition. 
     
     
         11 . The method of  claim 1 , further comprising initiating an alert upon detection of predetermined changes in the at least one respiratory parameter or upon detection of inadequate contact with the patient. 
     
     
         12 . The method of  claim 1 , further comprising filtering a first signal with a generator signal as a carrier and filtering a second signal with 90-degree phase rotating circuitry before demodulation. 
     
     
         13 . The method of  claim 1 , further comprising simultaneously measuring an electrocardiogram or impedance cardiography and impedance pneumography. 
     
     
         14 . The method of  claim 1 , wherein the sensor is a bipolar or tetrapolar impedance sensor with one or more measurement channels placed on the abdomen or thorax of the patient. 
     
     
         15 . The method of  claim 14 , wherein the calibration coefficient is derived from one or more of the following patient specific measurements: total body impedance, bioelectrical impedance measurements, average or baseline impedance on the measurement channel, ECG signal acquired at various locations, anthropomorphic measurements. 
     
     
         16 . The method of  claim 1 , further comprising controlling adaptive electronics by a microprocessor, wherein the adaptive electronics maintain the gains on different amplifiers to prevent the signal from going out of range. 
     
     
         17 . The device of claim  38 , wherein the microprocessor tracks and adjusts the set gains at each of the amplifiers. 
     
     
         18 . The device of  claim 1 , wherein the programmable element controls, via a closed loop, at least one of a ventilator, an analgesia device, a medical device, or a therapy device. 
     
     
         19 . The device of  claim 1 , wherein the at least one respiratory measurement is combined with at least one of pulse oximety or capnography. 
     
     
         20 . The method of  claim 1 , wherein the step of automatically adjusts for the signal variation comprises automatically changing parameters of the y-axis of a display chart of a dataset. 
     
     
         21 . The method of  claim 1 , wherein the step of automatically adjusts for the signal variation comprises recalculating or adjusting the calibration coefficient when there is a change in at least one of baseline impedance, mean impedance, and respiratory rate.