Blood pressure is an important vital sign measured not only in hypertension but also among hospitalized patients for clinical evaluation of the actual hemodynamic status. In the digital era, mercury and aneroid sphygmomanometers are being replaced by automated monitors despite lacking validation and recommendations for their use, especially in acute illness.

To compare automated and manual blood pressure measurement among hospitalized medical patients with acute illness.

A crossover design was used in a single tertiary hospital. Blood pressure was recorded from 216 participants, with 432 observations from an automated monitor (Omron HBP1120) and a mercury sphygmomanometer. Automated and manual BP recordings were done twice following the same arm sequential method. The average of the two recordings was used for comparison.

Most participants were female, elderly, obese, and had cardiac complaints. Comparing automated and manual methods, the mean difference for systolic was 1.47 ± 12.12 (p = 0.08) and 1.82 ± 10.99 (p=0.02) for diastolic. Subgroup analysis revealed that males had higher manual systolic BP than females (pairwise p-value= 0.017). Overweight and obese participants had higher automated systolic and diastolic BP (p=0.04). Overweight and obese participants had significantly higher systolic and diastolic BP regardless of the method. Significantly higher diastolic BP for different age groups and areas of admission (p=0.02) were observed from the automated method.

Automated BP monitoring showed a significant difference in diastolic BP recordings. Automated BP monitors should be used with caution, especially in interpreting diastolic BP among hospitalized patients.