Accuracy and reliability of two indirect ambulatory blood pressure recorders: Remler M2000 and Cardiodyne Sphygmolog.

The Remler M2000 and Cardiodyne Sphygmolog are semiautomatic recorders designed to measure ambulatory blood pressure non-invasively. These recorders were assessed for accuracy and reliability in a study designed in three stages. Firstly, the interdevice variabilitv was assessed separately for each type of recorder by comparing the recordings of three devices against each other and against simultaneous recordings by a mercury standard in 12 patients, multiple recordings being made in a random order in each patient. The mercury standard used was the London School of Hygiene (LSH) sphygmomanometer and the Hawksley random zero sphygmomanometer during assessment of the Remler and Sphygmolog, respectively. Though there were no differences between the three Remler recorders tested, one Sphygmolog recorder gave higher recordings than the two other Sphygmolog recorders tested because of a zero drift of 3 to 4 mmHg in the pressure transducer. Remler recordings were higher than simultaneous LSH sphygmomanometer recordings for both systolic and diastolic pressures. In the second part of the study, the Remler was compared with the Hawksley using simultaneous recordings in the same arm in 58 patients. No difference was found between Hawksley and Remler recordings. The discrepancy between this and the Remler-LSH comparison resulted from a tendency for the LSH sphygmomanometer to underestimate blood pressure. Similarly, the Sphygmolog recordings were compared with simultaneous Hawksley recordings in 100 patients. No significant difference was found between paired systolic pressure recordings though Sphygmolog recordings underestimated diastolic blood pressure. In the third part of the study, the reliability of the Remler was assessed from 69 attempted day recordings. Five Remler day recordings failed, a major cause of lost recordings being a defect in the microphone lead. The reliability of the Sphygmolog was compared with the Remler by attempting day recordings with each device in 13 patients. The reliability of the Sphygmolog was significantly poorer, only five of 13 Sphygmolog day recordings being decodable because of dislodgement of the recording disc during ambulation.