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A method of obtaining an indication of the position of an esophageal catheter inserted into a patient includes the steps of obtaining an electrical signal from the esophageal catheter, determining an ECG component of the electrical signal, determining the widths and/or rate of a number of periods in

A method of obtaining an indication of the position of an esophageal catheter inserted into a patient includes the steps of obtaining an electrical signal from the esophageal catheter, determining an ECG component of the electrical signal, determining the widths and/or rate of a number of periods in which the ECG component exceeds a threshold value, using the rate or widths of the periods to determine the presence of a P-wave in the ECG component, and concluding that the catheter is in a good position for obtaining a correct EMG signal if a P-wave is determined to be present. If not, the position may be corrected. The method may be performed by a control unit in a ventilator or a monitoring device.

대표청구항 ▼

1. A method for obtaining an indication of the position of an esophageal catheter inserted into a patient, comprising the steps of: obtaining an electrical signal from electrodes carried by an esophageal catheter inserted in the esophagus of a subject;supplying said electrical signal to a processor

1. A method for obtaining an indication of the position of an esophageal catheter inserted into a patient, comprising the steps of: obtaining an electrical signal from electrodes carried by an esophageal catheter inserted in the esophagus of a subject;supplying said electrical signal to a processor and, in said processor, automatically extracting an ECG component from said electrical signal;in said processor, determining a number of periods during which said ECG component exceeds a threshold value;in said processor, determining whether a P-wave is present in said ECG component dependent on at least one of a width and a rate of said number of periods; andwhen said P-wave is determined by said processor to be present in said ECG component, emitting an output signal from said processor indicating that the catheter is in a position in the patient for obtaining a correct EMG signal. 2. A method as claimed in claim 1 comprising, in said processor, using said widths of said periods to determine a presence of said P-wave close to a QRS complex. 3. A method as claimed in claim 1 comprising, in said processor, determining that said P-wave is present in said ECG component if one of a two most frequent widths of said period exceeds a predetermined limit value. 4. A method as claimed in claim 1 comprising, in said processor, determining that said P-wave is present in said ECG component if more than a predetermined fraction of said widths of said period are between a lower limit value and an upper limit value. 5. A method as claimed in claim 1 further comprising: in said processor, determining a rate of occurrence of said periods;detecting a heart rate of the patient and supplying a heart rate signal representing the heart rate to said processor;in said processor, comparing said rate of occurrence of said periods to said heart rate; andin said processor, determining that a P-wave is present in said ECG component if the rate of occurrence of the periods is approximately twice said heart rate. 6. A method as claimed in claim 1 further comprising, if no P-wave is determined by said processor to be present in said ECG component, automatically identifying and analyzing, in said processor, a further characteristic of the patient indicative of a position of said catheter. 7. A method as claimed in claim 6 wherein said processor analyzes a NEX value as said further characteristic. 8. A non-transitory, computer-readable storage medium loaded into a processor supplied with an electrical signal from a esophageal catheter inserted into a patient, said computer-readable medium being encoded with programming instructions and said programming instructions causing said processor to: obtain an electrical signal from electrodes carried by an esophageal catheter inserted in the esophagus of a subject;automatically extract an ECG component from said electrical signal;determine a number of periods during which said ECG component exceeds a threshold value;determine whether a P-wave is present in said ECG component dependent on at least one of a width and a rate of said number of periods; andwhen said P-wave is determined to be present in said ECG component, emit an output signal indicating that the catheter is in a position in the patient for obtaining a correct EMG signal. 9. A non-transitory, computer-readable storage medium as claimed in claim 8 wherein said programming instructions further cause said processor to use said widths of said periods to determine a presence of P-wave close to a QRS complex. 10. A non-transitory, computer-readable storage medium as claimed in claim 8 wherein said programming instructions further cause said processor to determine that a P-wave is present in said ECG component if one of a two most frequent widths of said period exceeds a predetermined limit value. 11. A non-transitory, computer-readable storage medium as claimed in claim 8 wherein said programming instructions further cause said processor to determine that a P-wave is present in said ECG component if more than a predetermined fraction of said widths of said period are between a lower limit value and an upper limit value. 12. A non-transitory, computer-readable storage medium as claimed in claim 8 wherein said programming instructions further cause said processor to: determine a rate of occurrence of said periods;detect a heart rate of the patient and supplying a heart rate signal representing the heart rate to said processor;compare said rate of occurrence of said periods to said heart rate; anddetermine that a P-wave is present in said ECG component if the rate of occurrence of the periods is approximately twice said heart rate. 13. A control unit for controlling a ventilator, said control unit comprising: An input adapted to receive an electrical signal from electrodes carried by an esophageal catheter inserted in the esophagus of a subject;an output;a processor that automatically extracts an ECG component from said electrical signal;said processor being configured to determine a number of periods during which said ECG component exceeds a threshold value;said processor being configured to determine whether a P-wave is present in said ECG component dependent on at least one of a width and a rate of said number of periods; andsaid processor being configured, when said P-wave is determined by said processor to be present in said ECG component, to emit an output signal at said output indicating that the catheter is in a position in the patient for obtaining a correct EMG signal. 14. A ventilator for providing breathing support to a patient, comprising: a breathing circuit adapted for interaction with a patient to provide breathing support to the patient;a control unit that controls operation of said breathing circuit, including operation in an EMG-controlled mode;said control unit having an input adapted to receive an electrical signal from electrodes carried by an esophageal catheter inserted in the esophagus of a subject, and said control unit having an output and a processor connected between said input and output;said processor being configured to automatically extract an ECG component from said electrical signal;said processor being configured to determine a number of periods during which said ECG component exceeds a threshold value;said processor being configured to determine whether a P-wave is present in said ECG component dependent on at least one of a width and a rate of said number of periods; andsaid processor being configured, when said P-wave is determined by said processor to be present in said ECG component, to emit an output signal from said processor indicating that the catheter is in a position in the patient for obtaining a correct EMG signal to allow said operation of said breathing circuit in said EMG-controlled mode. 15. A ventilator and esophageal catheter assembly for providing breathing support to a patient, comprising: an esophageal catheter adapted to be inserted in the esophagus of a subject, said esophageal catheter comprising a plurality of electrodes that generate an electrical signal while the esophageal catheter is in said esophagus;a breathing circuit adapted for interaction with a patient to provide breathing support to the patient;a control unit that controls operation of said breathing circuit, including operation in an EMG-controlled mode;said control unit having an input connected to said esophageal catheter to receive said electrical signal from said electrodes, and said control unit having an output and a processor connected between said input and said output;said processor being configured to automatically extract an ECG component from said electrical signal;said processor being configured to determine a number of periods during which said ECG component exceeds a threshold value;said processor being configured to determine whether a P-wave is present in said ECG component dependent on at least one of a width and a rate of said number of periods; andsaid processor being configured, when said P-wave is determined by said processor to be present in said ECG component, to emit an output signal from said processor indicating that the catheter is in a position in the patient for obtaining a correct EMG signal to allow said operation of said breathing circuit in said EMG-controlled mode.