shown in fig1 a these sensors detect acceleration over a range of u2212 2 g or alternatively up to u2212 8 g with a small scale low power circuit many patient 39 s are classified as u2018 abdomen breathers u2019 meaning during respiration their abdomen undergoes larger movements than their chest a relative minority of patients are u2018 chest breathers u2019 indicating that it is the chest that undergoes the larger movements for this reason it is preferred that rr is determined using an acc waveform detected along the z axis with an accelerometer 14 positioned on the patient 39 s abdomen in alternate configurations the accelerometer 12 on the chest can be used in its place or two augment data collected with the abdomen mounted sensor typically acc waveforms along multiple axes e g the x and y axes are also modulated by breathing patterns and can thus be used to estimate rr in still other configurations multiple signals from one or both accelerometers 12 14 are collectively processed to determine a single u2018 effective u2019 acc waveform representing e g an average of the two waveforms this waveform is then processed using adaptive filtering to determine the patient 39 s rr as shown in fig2 a and 2b ecg waveforms are simultaneously measured with the acc waveforms using a trio of electrodes 20 22 24 typically positioned on the chest of the patient 10 in an einthoven 39 s triangle configuration during a measurement each electrode 20 22 24 measures a unique analog signal that passes through a shielded cable to an ecg circuit 26 which is typically mounted in a small plastic box 25 attached to the patient 39 s chest the ecg circuit 26.