Electrocardiograph leads-off indicator

A leads-off indicator for an ECG apparatus comprising:

• (a) a plurality of electrodes adapted for attachment to a patient's body at predetermined locations for picking up signals and noise, said locations including the left arm (LA), right arm (RA), left leg (LL), right leg (RL) and chest (V) to define lead vector I as a potential difference between RA and LA electrodes, lead vector II as a potential difference between RA and LL electrodes, lead vector III as a potential difference between LA and LL electrodes and precordal vector V as a potential difference between V electrode and an average of the ECG signals at RA, LA and LL electrodes;
• (b) detector means coupled to said plurality of electrodes for first detecting whether the RL electrode is connected to the patient and, if so, applying a drive signal to the patient, via the RL electrode, the drive signal being derived from ECG signals and ambient noise picked up by the LL, LA and RA electrodes;
• and
• (c) means for comparing a level of ambient noise on each of said vectors to assess whether a particular one of the RA, LA and LL electrodes is not properly contacting the patient.

A leads-off indicator for an ECG apparatus comprising:

• (a) a plurality of electrodes adapted for attachment to a patient's body at predetermined locations for picking up signals and noise, said locations including the left arm (LA), right arm (RA), left leg (LL), right leg (RL) and chest (V) to define lead vector I as a potential difference between RA and LA electrodes, lead vector II as a potential difference between RA and LL electrodes, lead vector III as a potential difference between LA and LL electrodes and precordal vector V as a potential difference between V electrode and an average of the ECG signals at RA, LA and LL electrodes;
• (b) means including the RL electrode for applying a drive signal derived from ECG signals and ambient noise picked up by the LL, LA and RA electrodes;
• and
• (c) means for comparing a level of ambient noise on each of said vectors to assess whether a particular one of the RA, LA and LL electrodes is not properly contacting the patient.

A leads-off indicator for an ECG apparatus, comprising:

• (a) a plurality of electrodes LL, LA, RA adapted for attachment to the left leg, left arm and right arm, respectively, said electrodes exhibiting a skin-electrode impedance including a resistive component and a reactive component;
• (b) difference amplifiers coupled to two of the LL, the LA and the RA electrodes for producing an output signal proportional to the potential difference between said two electrodes, the potential difference including a common-mode noise component;
• (c) a feedback circuit coupled between the output of each of the difference amplifiers and the resistive and reactive components of the skin-electrode impedance of one of said two electrodes, the feedback circuit effectively varying attenuation of the resistive and reactive components to minimize the common-mode noise component;
• and
• (d) logic means responsive to a signal developed by either of the feedback circuits for indicating when one of the RA, LA and LL electrodes is not properly attached to the patient.

A method of detecting and identifying which of a plurality of ECG electrodes is not properly affixed to the body of a patient comprising the steps of:

• (a) providing a plurality of ECG leads, each having an electrode intended to be affixed to the patient's body at a predetermined location, the potential difference between selected pairs of said electrodes defining ECG vectors, at least one of the electrodes being a reference electrode;
• (b) detecting if the reference electrode is properly coupled to the patient;
• (c) driving the reference electrode with a signal proportional to ambient noise picked up by the electrodes;
• and
• (d) comparing common mode noise voltage levels present in said ECG vectors with a predetermined threshold voltage to determine whether a particular one of the electrodes, other than the reference electrode, is improperly affixed to the patient at its intended location.