Development and modelling of arterial applanation tonometry: a review

Arterial tonometry allows non-invasive and continuous registration of the arterial pressure waveform, by applanating (flattening) a superficial artery supported by bone with an external transducer. Inspired by ocular tonometry used for eye disease diagnosis, G.L. Pressman and P.M. Newgard built the first arterial tonometer in 1963, and derived a discrete, linear mechanical model. Accuracy remained poor until new sensor production techniques (silicon technology) arrived. G.M. Drzewiecki et al. published a second, more elaborate theoretical model for tonometer positioning in 1983. Few years later, the first modern tonometers were commercialised. Although the problems of sensor positioning, motion artefacts and calibration still exist, the tonometer has proven its usefulness in arterial compliance and hypertension studies. Attention should now go to analysis of the arterial pressure waveforms, and the combination with other signals (e.g. flow wave morphology) to allow a complete non-invasive haemodynamical description of the heart and the arterial tree.