Electrocardiogram (ECG) compression techniques are compared, and a unified view of these techniques is established. ECG data compression schemes are presented in two major groups: direct data compression and transformation methods. The direct data compression techniques are ECG differential pulse code modulation (DPCM) and entropy coding, AZTEC, Turning-point, CORTES, Fan and SAPA algorithms, peak-picking, and cycle-to-cycle compression methods. The transformation methods include Fourier, Walsh, and Karhunen-Loeve transforms. The theoretical bases behind the direct ECG data compression schemes are presented and classified into three categories: tolerance-comparison compression, DPCM, and entropy coding methods. A framework for evaluation and comparison of ECG compression schemes is presented. >

ECG data compression techniques-a unified approach

A method of locating a tip of a central venous catheter (“CVC”) having a distal and proximal pair of electrodes disposed within the superior vena cava, right atrium, and/or right ventricle. The method includes obtaining a distal and proximal electrical signal from the distal and proximal pair of electrodes and using those signals to generate a distal and proximal P wave, respectively. A deflection value is determined for each of the P waves. A ratio of the deflection values is then used to determine a location of the tip of the CVC. Optionally, the CVC may include a reference pair of electrodes disposed within the superior vena cava from which a reference deflection value may be obtained. A ratio of one of the other deflection values to the reference deflection value may be used to determine the location of the tip of the CVC.

Method of locating the tip of a central venous catheter

A guidance system for assisting with the insertion of a needle into a patient body is disclosed. The guidance system utilizes ultrasound imaging or other suitable imaging technology. In one embodiment, the guidance system comprises an imaging device including a probe for producing an image of an internal body portion target, such as a vessel. One or more sensors are included with the probe. The sensors sense a detectable characteristic related to the needle, such as a magnetic field of a magnet included with the needle. The system includes a processor that uses data relating to the sensed characteristic to determine a 3-D position of the needle. The system includes a display for depicting the position of the needle. In other embodiments, a guidance system for guiding rigid or other medical instruments is disclosed, together with various example implementations thereof.

Systems and methods for guiding a medical instrument

An integrated catheter placement system for accurately placing a catheter within a patient's vasculature is disclosed. In one embodiment, the integrated system comprises a system console, a tip location sensor for temporary placement on the patient's chest, and an ultrasound probe. The tip location sensor senses a magnetic field of a stylet disposed in a lumen of the catheter when the catheter is disposed in the vasculature. The ultrasound probe ultrasonically images a portion of the vasculature prior to intravascular introduction of the catheter. The ultrasound probe includes user input controls for controlling use of the ultrasound probe in an ultrasound mode and use of the tip location sensor in a tip location mode. In another embodiment, ECG signal-based catheter tip guidance is included in the integrated system to enable guidance of the catheter tip to a desired position with respect to a node of the patient's heart.

Integrated System for Intravascular Placement of a Catheter

A guidance system for assisting with the insertion of a needle into a patient body is disclosed. The guidance system utilizes ultrasound imaging or other suitable imaging technology. In one embodiment, the guidance system comprises an imaging device including a probe for producing an image of an internal body portion target, such as a vessel. One or more sensors are included with the probe. The sensors sense a detectable characteristic related to the needle, such as a magnetic field of a magnet included with the needle. The system includes a processor that uses data relating to the sensed characteristic to determine a 3-D position of the needle. The system includes a display for depicting the position of the needle. The needle can include a donut-shaped magnet disposed about the needle cannula, or a removable stylet with a magnetic element and a strain gauge for detection of the needle distal tip.

Apparatus for Use with Needle Insertion Guidance System

The power spectral densities of the electrocardiograms (ECGs) of seven patients in a coronary care unit were examined. It was discovered that the underlying periodic phenomenon is characterized by only one frequency, the heart rate, and that invariably by the fifteenth multiple of this fundamental frequency almost all the power is accounted for. Periodic approximations to the ECG based on 7, 10, and 15 harmonics were reconstructed; the fifteenth multiple of the fundamental frequency gave an excellent fit to the actual ECG for each patient. The ECGs were also reconstructed based on the frequencies corresponding to peaks greater than a designated fraction of the peak at the fundamental frequency; 104 elements were required to produce reconstruction comparable to the periodic approximations based on 15 harmonics. In addition, the power spectral densities of the individual waves of the PQRST cycle were determined and analyzed. This method provides an accurate description of the characteristic ECG and the practicality of its application to ECG monitoring for arrhythmia detection is being investigated.

Steven Salzberg

Papers

Analysis of power spectral densities of electrocardiograms