Apparatus and method for reduction of motion artifact

A patient monitoring system comprising:

• at least one pair of physiological recording electrode assemblies, each physiological recording electrode assembly of said at least one pair of physiological recording electrode assemblies having,
• a foam pad having a front surface for contacting the skin and a rear surface,
• said foam pad having a central region which is recessed on said front surface forming a central recess,
• a pad passage connecting said central recess to said rear surface of said foam pad,
• an electrode which transmits physiological signals, said electrode having a sensing end and a connector end,
• said electrode residing in said pad passage such that said sensing end resides in said central recess while said connector end protrudes from said pad passage,
• a clip attaching to said connector end of said electrode,
• a lead wire connected to said clip,
• at least one deformation gauge for providing deformation signals, said at least one deformation gauge being coupled to said foam pad;
• an electrode signal processor for each of said at least one pair of physiological recording electrode assemblies, said electrode signal processor being connected to said lead wires of said physiological recording electrode assemblies for receiving said physiological signals and providing amplified differential physiological signals;
• a deformation signal processor for each of said at least one deformation gauges, said deformation signal processor generating processed deformation signals from said deformation signals;
• a multiplexor for selectively passing said amplified differential physiological signals and said processed deformation signals;
• an A-to-D Converter for digitizing said amplified differential physiological signals and said processed deformation signals providing digital differential physiological signals and digital deformation signals;
• a microprocessor for receipt of said digital differential physiological signals and said digital deformation signals;
• and
• an adaptive noise canceling algorithm for instructing said microprocessor to combine said digital differential physiological signals and said digital deformation signals to provide filtered digital physiological signals.

A method for increasing the reliability of signals from skin-mounted physiological recording electrodes mounted to the skin of a patient, the method comprising the steps of:

• attaching a pair of skin-mounted physiological recording electrodes to the skin with foam pads;
• monitoring physiological signals received from said pair of physiological recording electrodes;
• calculating a differential physiological signal which is defined as the difference between said physiological signals from said pair of physiological recording electrodes;
• mounting at least one deformation gauge on each of said foam pads;
• monitoring deformation signals which are correlated to the deformation of said at least one deformation gauge;
• and
• performing an adaptive noise cancellation on said differential physiological signal using said deformation signals to provide a noise-free differential signal.