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

To clarify the relationship between blood pressure and pulse wave transit time at the peripheral artery from the R wave of the electrocardiogram (m-PWTT), the effects of cardiovascular interventions on this relationship was evaluated.

Ten mongrel dogs were anesthetized by isoflurane inhalation, and catheter tip pressure transducers were inserted into the ascending aorta and at the bifurcation of abdominal aorta to measure central and peripheral pulse wave arrival. Pulse wave arrival at the ascending aorta from the R wave represents pre-ejection period (PEP) and pulse wave arrival between the ascending aorta and bifurcation of aorta represents pulse wave transit time (PWTT), thus m-PWTT = PEP + PWTT. Hypertension was induced by the continuous infusion of dobutamine and phenylephrine, and hypotension was induced by deepening isoflurane anesthesia, acute blood loss and nitroglycerine infusion. The relationship between timing components (PWTT, PEP, and m-PWTT) and blood pressure was recorded and analyzed by using the least squares method.

The relationship between timing components (PWTT, PEP and, m-PWTT) and blood pressure was significant and highly correlated. When the change in blood pressure was due to the myocardial contractility, such as after dobutamine infusion, the relationship between all timing components and blood pressure was consistent and negative. However, when the change in blood pressure was due to the vasoactive agents, such as phenylephrine, the relationship between timing components and blood pressure was dependent on the reflex change in PEP.

Change in m-PWTT is a good parameter to predict blood pressure changes, although the absolute blood pressure value cannot be obtained.