Criteria in the choice of an occluding cuff for the indirect measurement of blood pressure

For a sphygmomanometric method of indirect blood-pressure measurement to be accurate, the cuff must operate so that the intrabladder pressure is always the same as the pressure applied by the tissues of the arm to the artery wall. To determine under what conditions this occurs, analyses are presented assuming the arm to be a rotationally symmetric, incompressible solid cylinder acted upon by various cuff pressure fields. The results indicate that the pressure applied to the artery wall is markedly influenced by longitudinal motion of the arm tissue, which must be constrained to have an accurate pressure transmission. It is shown that a wide cuff does effectively accomplish this under its central region. The analyses agree with experiments in which indirect and direct blood-pressure measurements were made and most of the clinical observations of others. However, the claim that ‘if the cuff is too wide, the reading will be erroneously low’ is not indicated in the analytical solution and has not been observed in the authors' experiments. These analytical and experimental results were used to establish criteria for the design of appropriate occluding cuffs. Based upon these criteria, cuffs for clinical use have been produced from a plastic film in a variety of lengths and widths.