Direct and indirect blood pressure in critical care patients

The purpose of this study was to determine the relationship between direct intraarterial blood pressure readings and indirect auscultated blood pressure readings by using different listening pieces and auscultation sites. The two listening pieces used for correlation and comparison were the bell and the diaphragm of the stethoscope. The two sites for auscultation were the antecubital fossa and the upper arm immediately superior to the internal medial condyle and medial to the biceps tendon. Simultaneous direct and indirect blood pressure readings were obtained from 50 critical care patients with indwelling radial arterial lines. The averages for three blood pressure readings obtained from each site and for each listening piece were correlated and compared with the averages of three simultaneous direct blood pressure readings. Statistical testing was done separately for systolic and diastolic readings. Auscultation techniques using both listening pieces and sites were found to be accurate, r greater than .8 for all correlations; p less than .0001 for all comparisons, but auscultation using the diaphragm of the stethoscope over the brachial artery in the upper arm provided the most accurate readings.