Changes induced in the lower- and upper-limb pulse transit-time ratio during inspiratory resistive breathing

The ankle brachial index (ABI) has been widely used to monitor the pathogenesis of peripheral arterial diseases such as ischemia of the extremities. Owing to the occluding nature of ABI measurement, this may not be appealing to less cooperative patients when multiple prolonged screening is required. Recently, a simple non-occluding technique termed pulse transit-time ratio (PTTR) has shown potential as a surrogate ABI marker. It is also known that abrupt changes in inspiratory efforts can lead to increased blood pressure (BP) and heart rate. Since transit-time measurements can be confounded by these parameters, it is important to understand their effects on PTTR normality. We recruited 12 healthy adults (8 males, aged 27.0+/-3.1 years) to perform three inspiratory activities. Friedman and Wilcoxon statistical results both showed that significant changes in transit-time oscillations were observed for higher inspiratory loads (p<0.05). These results were verified by a corresponding air-pressure difference measurement, for which a similar significant increase was also registered (p<0.05). However, limited changes were observed in the derived PTTR parameter (p>0.05). These findings suggest that, similar to ABI, PTTR is only confounded by abnormal local changes in either of the peripheral BPs measured.