The relationship between modified pulse wave transit time and cardiovascular changes in isoflurane anesthetized dogs

Objective.To clarify the relationship between blood pressure andpulse wave transit time at the peripheral artery from the R wave of theelectrocardiogram (m-PWTT), the effects of cardiovascular interventions onthis relationship was evaluated. Methods.Ten mongrel dogs wereanesthetized by isoflurane inhalation, and catheter tip pressure transducerswere inserted into the ascending aorta and at the bifurcation of abdominalaorta to measure central and peripheral pulse wave arrival. Pulse wave arrivalat the ascending aorta from the R wave represents pre-ejection period (PEP)and pulse wave arrival between the ascending aorta and bifurcation of aortarepresents pulse wave transit time (PWTT), thus m-PWTT = PEP + PWTT.Hypertension was induced by the continuous infusion of dobutamine andphenylephrine, and hypotension was induced by deepening isoflurane anesthesia,acute blood loss and nitroglycerine infusion. The relationship between timingcomponents (PWTT, PEP, and m-PWTT) and blood pressure was recorded andanalyzed by using the least squares method. Results.The relationshipbetween timing components (PWTT, PEP and, m-PWTT) and blood pressure wassignificant and highly correlated. When the change in blood pressure was dueto the myocardial contractility, such as after dobutamine infusion, therelationship between all timing components and blood pressure was consistentand negative. However, when the change in blood pressure was due to thevasoactive agents, such as phenylephrine, the relationship between timingcomponents and blood pressure was dependent on the reflex change in PEP.Conclusions.Change in m-PWTT is a good parameter to predict bloodpressure changes, although the absolute blood pressure value cannot beobtained.