Testing five-day average ward based BP accuracy by comparing versus inpatient Ambulatory Blood Pressure Monitoring– A ward-based, retrospective cohort study

Abstract

Background Blood pressure (BP) is a highly important inpatient vital sign. However, its variability poses a challenge to the clinician attempting to conclude ward mean and minimum values - often from two readings per day. In this study we compared BP readings from 24-hour ambulatory BP monitors (ABPMs with that of 5 days of twice daily ward based BP readings (WBRs). The aim of the study was to test the accuracy of ward BP in clarifying mean and minimum values. Methods We performed a retrospective cohort study, gathering data on inpatients in an off-site rehabilitation unit between April 2023 and October 2024. Included patients had undergone an 24-hour ABPM assessment during their inpatient stay. Chart review was performed to collect data on ABPM, daytime WBRs (five day average, five day minimum), demographics, comorbidities, and clinical frailty score. Univariate analysis compared the relationships between ABPMsand WBRs. Results 72 patients were included; 45 were male (63%), mean age 79.92 years (6.744), mean clinical frailty score 5.056 (0.948). ABPMsdiffered significantly from five-day WBRs. Mean Systolic WBRs differing from ABPMsby an average of 6.4mmHg (p-value 0.03, Pearson 0.79). WBRs overestimated systolic blood pressure in 50 patients (69%), by an average of 12.01mmHg (p-value 0.001, Pearson 0.9). Regarding minimum Systolic BP, WBRs overestimated minimum BP by more than 10mmHg in 35 (49%) patients. Of note 29 (40%) of our cohort reported a history of falls in the last year with comorbid orthostatic hypotension. Conclusion In this frail, frequent-faller group, five-day average ward systolic BP overestimated mean systolic BP by approximately 1 BP tablet (6mmHg). Moreover, in half of patients ward BP overestimated minimum BP by more than 10mmHg. While treating hypertension is an essential component of medical care, more accurate BP assessment tools should be considered to prevent over-zealous treatment of BP in older, frailer inpatients.