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A model describing the rotation of the cardiac vector as a possible mechanism for the presence of respiratory information in the ECG is discussed. The way in which this information is revealed is analyzed, and the predictions subjected to qualitative experimental assessment via spectral analysis. The results show that respiratory frequencies occur in the ECG spectrum as a result of heart movement. Measurements on a patient wearing a pacemaker and ventilated to control respiratory rate show that even in the absence of respiratory sinus arrhythmia there is baseband information in the ECG spectrum, attributable neither to electrode artifacts nor to EMG, and sidebands from the respiratory cycle.