Abstract
(1) Frank vectorcardiographic P loops of 25 healthy males were recorded at deep inspiration and expiration by using a minicomputer system with an averaging technique. Respiratory changes in 21 P parameters were quantitatively investigated.
(2) The maximal left component of the P loop, the magnitude of the horizontal maximal vector and the magnitude of the P polar vector significantly decreased at deep inspiration as compared with those at expiration. The frontal and the spatial maximal vectors were significantly deviated vertically at deep inspiration as compared to those at expiration.
(3) It was considered to be better to obtain P loops at a particular phase of respiration or to use those obtained by an averaging technique in order to analyse P loop in detail in various heart diseases, especially in the exercise stress test associated with rapid deep respiration.
(4) The mechanism of respiratory P loop changes was discussed.
