Observing the brachial artery through a pressure cuff

Compression of the brachial arteryin vivo

Stiffening of the brachial artery is implicated in pseudo-hypertension. To date, a reliable clinical predictor of the condition has not been developed. This paper describes the development of prototype instrumentation and methodology for measurement of the brachial artery transmural pressure/cross-sectional area relationship in vivo. The methodology has been validated using a model of an arm and a thin-walled rubber tube. Application of the technique to a healthy subject shows that the technique is viable and gives good reproducibility. Closure of the brachial artery with reducing transmural pressure is observed and recorded. The new technique has some important advantages over existing methodologies.

Pseudo-hypertension and arterial stiffness: a review

Hypertension is a condition of persistently elevated blood pressure, associated with increased cardiovascular risk. Non-invasive BP measurement using Korotkoff sounds is the most common method of screening for the condition. The possibility of inaccurate readings leading to a false diagnosis of hypertension (pseudo-hypertension) is of concern. Stiffened arteries in the elderly have been proposed as being the primary cause of pseudo-hypertension. Non-invasive detection of pseudo-hypertension remains problematic. This paper reviews clinical literature on pseudo hypertension and approaches to measuring the compressive stiffness of arteries, as well as biomechanical literature regarding models of arterial stiffness and the origin of Korotkoff sounds. Models of the latter show the importance of the relationship between transmural pressure and cross-sectional area (P1/Csa curve) of the brachial artery as it closes under the influence of the pressure cuff. The review concludes that future research on pseudo-hypertension should include development of new instrumentation to measure the P1/Csa curve of the brachial artery in vivo using non-invasive techniques suitable for application to an elderly population.

Measurement of arterial closing pressure

It has been suggested that certain artifacts in blood pressure measurement by auscultation stem from stiffness of the tissues underneath the pressure cuff, resulting in a component of cuff pressure being required to overcome resistance to brachial artery collapse. This paper describes a technique for measuring the pressure required to collapse a segment of the brachial artery which has been isolated from central arterial pressure. This measurement is termed the arterial closing pressure. In a study of eleven elderly subjects, the artery collapsed spontaneously (zero closing pressure) after being isolated from central pressure in seven subjects. The remaining four required external pressures ranging from 4.6 to 10.7 kPa (35 to 81 mmHg) in order to collapse the artery. Thus arterial closing pressure may frequently be a significant fraction of arterial blood pressure in the elderly population, and may contribute to error in the measurement of blood pressure by auscultation. Arterial closing pressure may be a useful tool for investigating the origin of differences between indirect and direct blood pressure measurements, and also in the investigation of spontaneous arterial closure.