[Effect of nonpathological factors on the atrial segment of an orthogonal ECG in healthy persons]

The effect of deep breathing and shifting of the electrodes along the horizontal line was followed up in four orthogonal ECG systems. The duration of P wave did not change during deep breathing. The amplitude of P wave increased in the traditional ECG, simulating right atrial loading in the traditional ECG. The amplitude of Px decreased in OECG but it cannot lead to diagnostic difficulties. With the shifting of the electrodes (within the involuntary errors) OECG systems of McFee--Parungao and SVEK III are not liable to shifting of the electrodes and that of Frank shows an increase of the amplitude of the negative part of P z as in right-atrial loading.