Comparison between oscillometric and auscultatory methods of ambulatory blood pressure measurement in hemodialysis patients.

INTRODUCTION: 24-hour ambulatory blood pressure monitoring (ABPM) is commonly used in clinical and research practice. Different methods have been used in BP recording, cuff-oscillometric or Korotkoff sound, and validation studies during ABPM have been performed on general as well as hypertensive populations. Hemodialysis (HD) patients have a high percentage of complications, such as vascular diseases, and they are subject to hyperkinetic blood flows and abrupt body weight changes secondary to HD, which can invalidate BP recording. Therefore, we wanted to compare the 2 methods on an HD population.

PATIENTS AND METHODS: We performed 86 ABPMs on 44 patients (aged 60.8 +/- 17.2 years) by using a device capable of the simultaneous recording of oscillometric and auscultatory BP (A&D Takeda TM2421). The data obtained with the 2 different ABPM methods have been compared, and the differences between auscultatory and oscillometric determinations have been analyzed, as presented by Bland and Altman [1986].

RESULTS: The percentage of valid recordings was significantly higher with the oscillometric method than with the auscultatory method (93.6 +/- 11.3% vs. 71.7 +/- 17.04%, p < 0.001). 24-hour diastolic BP and night-time systolic BP were higher when recorded with the oscillometric method (DBP = 75.4 +/- 9.6 mmHg vs. 71.8 +/- 9.6 mmHg, p < 0.001, asleep SBP = 119.7+/-23.3 mmHg vs. 116.2 +/- 25.0 mmHg, p < 0.001), and the systolic night/day BP ratio was also higher(0.92 +/- 0.10vs.0.90 +/- 0.10, p < 0.001). Finally, the BP coefficient of variation ((SD/mean BP) x 100) was higher when auscultatory determinations were used (16.1 +/- 4.6 vs. 14.6 +/- 4.9). The limits of agreement between auscultatory and oscillometric BP determinations were for SBP = -6.44; 7.84 and for DBP = -3.66; 10.86.

CONCLUSIONS: Differences between 24-hour oscillometric and auscultatory ABPM were reported in HD patients: the diastolic 24-hour and asleep systolic BP values and the systolic night/day ratio obtained with the oscillometric method were significantly higher. The higher coefficient of variation reported with the auscultatory method and the wider limits of agreement suggest that the 2 methods do not fully coincide and, in our opinion, the oscillometric method is preferable, due to the higher number of 24-hour valid measurements.