Comparison of direct and indirect methods of measuring arterial blood pressure, part III.

Blood pressure measurements can be obtained in the clinical setting by a variety of methods, direct and indirect, but with varying results. Disparities between direct and indirect blood pressure measurements are due in part to physiological considerations, but are largely conditioned by the frequency response of the recording system. In this, the final part of a three-part series comparing blood pressure measuring techniques, the authors examine their own study of a group of patients undergoing surgery, and conclude that their study confirmed that was already known: direct measurements of systolic pressure correlate rather poorly with indirect measurements. In part I (Med. Instrum. January-February 1981), the authors concluded that comparative studies of direct and indirect blood pressure fall into two groups-those resulting in close agreement between methods, and those that do not. In part II (Med. Instrum. March-April 1981), they concluded that there is no easy solution to the problems confronting direct measurement of blood pressure, and that the, interim course seems to be insistence upon definition of the characteristics of measurement system employed in producing investigative data.