The Frank orthogonal corrected ECG and its first derivation were recorded in 27 healthy volunteers (women aged 19-22 years) during normal ventilation at rest (control group), after voluntary hyperventilation lasting 75 seconds, and during hypoxic-hypercapnic ventilation (through the enlarged dead space) lasting 5 min. The projections of the magnitude and direction of the positive and negative QRS derivation maxima into the horizontal, frontal, left sagittal planes and their spatial distribution were constructed. The magnitude of the positive and negative QRS derivation maxima was significantly decreased during hypoxic-hypercapnic ventilation. A significant alteration in the direction only arose at the positive maximum during hypoxic-hypercapnic ventilation in the frontal plane. The intrinsicoid deflection was not significantly altered. The normal values of the maxima of the first QRS derivation in young healthy women are given. It is supposed that the decrease in amplitude of the maxima of the first QRS derivation is caused by slowed propagation of the depolarization wave under hypoxic- hypercapnic conditions and alteration of the direction of the positive maximum is caused by a greater participation of the right ventricle at the origin of the resulting QRS vector.
The influence of some pulmonary ventilation alterations (the normal ventilation at rest = control), the hyperventilation (HV) lasting 75 s, the hypoxic-hypercapnic ventilation (HXV) lasting 3 and 6 min) on the instantaneous QRS vectors was investigated in 42 young healthy women (19-24 years old). The magnitude and the direction of instantaneous QRS vectors in the 10th to the 70th ms and in QRS max were constructed from the Frank lead ECG. The significant alterations of the direction (angle) were found in the 30th ms and QRS max at HXV and in the 60th ms at HV. A significant decrease in the magnitude of instantaneous vectors was found in the 10th to 50th ms after 6 min of HXV, in the 30th to 50th ms at 3 min of HXV, in the 40th to 50th ms at HV. These alterations were the most marked in the horizontal plane. We suggest that the alterations of the instantaneous QRS vectors were caused by the influence of the autonomic nervous system or humoral agents, but not by heart position, Brody’s effect or lung hyperinflation.