Blood pressure measurement in peritoneal dialysis: which method is best?

Abstract

Background: The optimal approach to monitoring blood pressure (BP) in the peritoneal dialysis (PD) population is unclear. Ambulatory BP monitoring reliably predicts prognosis, but can be inconvenient. The accuracy of home BP monitoring in this population is unproven. The automated BpTRU device (BpTRU Medical Devices, Coquitlam, BC, Canada), which provides an average of up to 6 successive in-office BP measurements, has not been studied in this patient group.

Methods: We studied 17 patients (average age: 54 ± 12 years; 12 men, 5 women; 94% on automated PD) attending a single center. All patients underwent office, home, BpTRU, and ambulatory BP measurement. The reference standard for analysis was daytime ambulatory BP. Correlation between the referent method and each comparator method was determined (Pearson correlation coefficient), and Bland-Altman scatter plots depicting the differences in the BP measurements were constructed.

Results: Mean office BP (126.4 ± 16.9/78.8 ± 11.6 mmHg) and BpTRU BP (123.8 ± 13.7/80.7 ± 11.1 mmHg) closely approximated mean daytime ambulatory BP (129.3 ± 14.8/78.2 ± 7.9 mmHg). Mean home BP (143.8 ± 15.0/89.9 ± 28.1 mmHg) significantly overestimated mean daytime systolic BP by 14.2 mmHg (95% confidence interval: 4.3 mmHg to 24.1 mmHg; p = 0.008). Bland-Altman plots demonstrated poorest agreement between home BP and daytime ambulatory BP. No patient had "white-coat hypertension," and only 1 patient had false-resistant hypertension. Most patients showed abnormal nocturnal dipping patterns (non-dipping: n = 11; reverse-dipping: n = 5; normal dipping: n = 1).

Conclusions: We report a novel finding that BP measurement using the BpTRU device is more accurate than home BP measurement in a PD population. Potential explanations for this observation include poor home BP measurement technique, use of poorly validated home BP measurement devices, or a reduced prevalence of white-coat effect among PD patients. Our study also confirms that, in the PD population, BP measurements vary considerably with patient location, time of day, and measurement technique.

Keywords: BpTRU; Hypertension; ambulatory; blood pressure; home; measurement.

Figures

Figure 1 —

Associations between daytime ambulatory systolic blood pressure (SBP) measurements and comparator measurements (in millimeters of mercury). Scatterplots show associations for comparator measurements (A) by BpTRU (BpTRU Medical Devices, Coquitlam, BC, Canada), r = 0.49, p < 0.05; (B) by office measurement, r = 0.45, p = 0.07; and (C) by home measurement, r = 0.24, p = 0.37.

Figure 2 —

Agreement between daytime ambulatory systolic blood pressure (SBP) and comparator measurements (in millimeters of mercury). Bland-Altman scatterplots show the mean of the ambulatory and comparator SBP measurements on the x axes and the difference of those readings on the y axes. Horizontal lines mark the mean difference in SBP between the methods and the upper and lower limits of the 95% confidence interval for that difference. (A) BpTRU (BpTRU Medical Devices, Coquitlam, BC, Canada) comparator measurement. (B) Office comparator measurement. (C) Home comparator measurement. ΔSBP = (SBP by comparator method) - (SBP daytime ambulatory measurement).