ADS192R respiration rate detection
They provide an extremely high impedance bias voltage, so the DC component of voltage present at IN1P is centered around the middle of the analog supply range. This is necessary to set the DC point for the measurements made by the ADC.

As you can see, it's only AC-coupled to the rest of the circuit; the various capacitors make sure of that. They are there to prevent DC current flowing in the patient under measurement.