Global versus local linear beat-to-beat analysis of the relationship between arterial pressure and pulse transit time during dynamic exercise
Global linear analysis has been traditionally performed to verify the relationship between pulse transit time (PTT) and systolic arterial pressure (SAP) at the level of their spontaneous beat-to-beat variabilities: PTT and SAP have been plotted in the plane (PTT,SAP) and a significant linear correlation has been found. However, this relationship is weak and in specific individuals cannot be found. This result prevents the utilization of the SAPPTT relationship to derive arterial pressure changes from PTT measures on an individual basis. We propose a local linear approach to study the SAPPTT relationship. This approach is based on the definition of short SAPPTT sequences characterized by SAP increase (decrease) and PTT decrease (increase) and on their search in the SAP and PTT beat-to-beat series. This local approach was applied to PTT and SAP series derived from 13 healthy humans during incremental supine dynamic exercise (at 10, 20 and 30% of the nominal individual maximum effort) and compared to the global approach. While global approach failed in some subjects, local analysis allowed the extraction of the gain of the SAPPTT relationship in all subjects both at rest and during exercise. When both local and global analyses were successful, the local SAPPTT gain is more negative than the global one as a likely result of noise reduction.
arterial pressure pulse transit time dynamic exercise cardiovascular variability