A medical device , comprising: a housing ; and a processor within the housing configured to: receive an input signal for a patient receiving chest compressions from a mechanical chest compression device , the mechanical chest compression device having a chest compression frequency f; receive an indication of the chest compression frequency f from the mechanical chest compression device; select at least one filter mechanism ; apply the at least one filter mechanism to the input signal to at least substantially remove chest compression artifacts from the input signal, wherein the chest compression artifacts correspond to the chest compressions being delivered to the patient by the mechanical chest compression device, and wherein the at least one filter mechanism substantially rejects content in the frequency f plus content in at least one more frequency that is a higher harmonic to the frequency f, and substantially passes frequencies between the frequency f and the higher harmonic; and suppress application of the at least one filter mechanism in response to determining that the mechanical chest compression device is no longer delivering chest compressions to the patient. a housing ; and a processor within the housing configured to: receive an input signal for a patient receiving chest compressions from a mechanical chest compression device , the mechanical chest compression device having a chest compression frequency f; receive an indication of the chest compression frequency f from the mechanical chest compression device; select at least one filter mechanism ; apply the at least one filter mechanism to the input signal to at least substantially remove chest compression artifacts from the input signal, wherein the chest compression artifacts correspond to the chest compressions being delivered to the patient by the mechanical chest compression device, and wherein the at least one filter mechanism substantially rejects content in the frequency f plus content in at least one more frequency that is a higher harmonic to the frequency f, and substantially passes frequencies between the frequency f and the higher harmonic; and suppress application of the at least one filter mechanism in response to determining that the mechanical chest compression device is no longer delivering chest compressions to the patient. receive an input signal for a patient receiving chest compressions from a mechanical chest compression device , the mechanical chest compression device having a chest compression frequency f; receive an indication of the chest compression frequency f from the mechanical chest compression device; select at least one filter mechanism ; apply the at least one filter mechanism to the input signal to at least substantially remove chest compression artifacts from the input signal, wherein the chest compression artifacts correspond to the chest compressions being delivered to the patient by the mechanical chest compression device, and wherein the at least one filter mechanism substantially rejects content in the frequency f plus content in at least one more frequency that is a higher harmonic to the frequency f, and substantially passes frequencies between the frequency f and the higher harmonic; and suppress application of the at least one filter mechanism in response to determining that the mechanical chest compression device is no longer delivering chest compressions to the patient. <EOS>