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Figure 1 An example of the effect of Salbutamol and glyceryl trinitrate (GTN) on the radial waveform in a single individual. It can be seen that the second systolic peak, obvious at baseline, is diminished by Salbutamol and almost completely abolished following GTN. The changes in the wave-shape are quantified using the augmentation index (AIx), calculated as the ratio of the pulse pressure at the second systolic peak to that at the first systolic peak. BP = blood pressure.