Method and apparatus for selecting differential input leads

An apparatus for acquiring physiological data from a patient, comprising:

• three or more leads (8, 12, 14, 18) structured to be placed on a body of the patient, each of the leads being adapted to collect a signal relating to a particular physiological parameter from the patient;
• at least one AC current source (54, 56);
• a switching mechanism (42, 44) structured to selectively couple the at least one AC current source to selected pairs of the leads such that at any one time the at least one AC current source will inject an AC current across only a current selected pair of the leads, wherein in response to the injected AC current, an AC voltage will be generated across the current selected pair of the leads;
• and
• a processing device (46) structured to (i) determine an impedance across the current selected pair of the leads based on the AC voltage, (ii) determine whether the impedance is less than a predetermined impedance threshold, (iii) if the impedance is less than the predetermined impedance threshold cause the current selected pair of the leads to be used for generating data relating to the particular physiological parameter;
• and (iv) if the impedance is not less than the predetermined impedance threshold cause the switching mechanism to couple the at least one AC current source to a new current selected pair of the leads such that the AC current is injected across the new current selected pair of the leads.