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Abstract

Pulse Transit Time (PTT) is the time it takes for an arterial pulsation to travel from the heart to a peripheral site. In recent times, PTT has been advocated as a marker for assessing increased vascular resistance. However, the reliability of PTT as a marker for cardiovascular risks and its inverse relation to beat-to-beat blood pressure is still being investigated. In order to validate the technique as a reliable marker of vascular resistance, PTT measurements were made using photoplethysmographic (PPG) signals obtained from multiple measurement sites in 12 healthy volunteers undergoing right hand immersion in ice water for 30 secs. PTT measurements were made from the ear canal (EC), the left (LIF) and right index fingers (RIF) using custom made photoplethysmographic probes. Activation of the sympathetic nervous system during the ice water immersion caused an increase in vascular resistance, which is associated with an increase in mean arterial pressure and a decrease in PTT in all measurement sites. However, the change in PTT was much larger in the RIF when compared to the LIF and the EC. This demonstrates the cerebral flow autoregulation and the profound peripheral vasoconstriction seen in the right hand. After the ice immersion period, the mean PTT measured from the EC returned to baseline, whereas the LIF PTTs exceeded baseline values. This is due to the local vasodilation resulted from the activation of a thermoregulatory mechanism.

Publication Type:	Article
Additional Information:	© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.
Publisher Keywords:	Science & Technology; Technology; Engineering, Biomedical; Engineering, Electrical & Electronic; Engineering
Subjects:	R Medicine > RC Internal medicine T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering

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