How to measure blood pressure in primary care offices to assure accuracy while maintaining efficiency

The measurement of vital signs is the standard of care for every patient in primary care physicians (PCP) offices and the usual care for most specialties. Vital signs include weight and blood pressure (BP) for each patient and height, pulse, finger oximetry, and temperature intermittently, as indicated. In 2015, there were an estimated 922.6 million physician office visits (https://www.cdc.govnchs/fastats/physician-visits.htm). Primary care physicians provided 331.2 million visits (53%) with the most commonly diagnosed condition.

Accuracy of BP measurement is taught in all medical, nursing, and medical assistant schools; however, these methods are seldom implemented in clinical practice. Why are two simple numbers so difficult to measure correctly in outpatient, inpatient, and emergency settings? Measuring BP correctly is a tedious, time‐consuming vital sign. I state this based on my experience of 36 years of performing more than 34 000 measurements, equating to 33 726 minutes of BP measurements (562 hours).

In the mid‐1990s, most hospital assessments of vital signs were silently transitioned from manual to automatic electronic measurement likely because of efficiency without expert guidelines nor clinical studies driving this change. Most research has also morphed to this method over the past decade. Similarly, this was a silent transition likely to avoid the errors inherent in the auscultatory method including rapid deflation, end‐zero bias, and mistakes caused by visual and hearing impairments. Office measurements have never been standardized and are more slowly transitioning, because of multiple factors, to the electronic methods depending on the specific office setting. The positive results of the largest BP outcome trial (SPRINT [Systolic Blood Pressure Intervention Trial]) of 9361 patients that solely used an electronic automatic device may increase the purchase of these types of devices in PCP offices to more effectively control hypertension.1

Numerous studies on both home and 24‐hour ambulatory BP monitoring have confirmed that their usage offers cardiovascular predictive prognostic value. Usual (nonresearch) office BP measurement practices provide no such proof. So, why then should we continue to measure BP in outpatient offices? First, diagnosis of new hypertension is considered by PCPs during visits for other concerns and office BP measurements initiate this suspicion. Office BP trends over time are important for furthering this suspicion, especially for highly variable isolated systolic hypertension and atrial fibrillation. New hypertension should always be diagnosed by out‐of‐office BP measurements, preferably by 24‐hour ambulatory BP monitoring (https://www.nice.org.uk/guidance/cg127/evidence/full-guideline-pdf-8949179413).1, 2 Second, nonstandardized office BP measurement, if “normal,” will likely be lower if measured correctly, saving office time for most patients. The difference between usual outpatient BP measurement and the strict proper technique has been shown to be 9–12/6–7 mm Hg (P < .01).3, 4 Third, some patients with hypertension need their treatment deescalated because of hypotension, especially in patients with high fall risks. Office measurement could screen these patients, some of whom are not able to monitor their own home BP.

In our office, the medical assistant (MA) rooming time, prior to the physician interaction, is between 5 and 10 minutes per patient. The auscultatory measurement of 58.6 seconds, based on my practice research, is thus 10% to 20% of the MA time to room the patient. Canada has been actively funding and promoting automatic electronic BP monitoring without an observer present, and the 2016 guidelines state that this is the preferred method.5, 6 This method could decrease the rooming MA time as it uses an often limited examination room resource for 5 to 6 minutes. The fixed cost of an examination room is variable; however, it is likely only $0.02 to 0.05 per minute of usage. If there are limited examination rooms, as is often the case, the lost opportunity of using this room for physician billing could cost $35 to $41 for 7 to 8 minutes of room usage, which is substantial for a PCP office.

Could future BP measurement devices be used in the lobby prior to the visit during the patient wait? I measured BP in 235 patients in the examination room and in the waiting room afterwards using an automatic BP monitor and found no significant difference (0/0 mm Hg, P > .05).4 Similarly, BP measured in the waiting room in a separate 100‐square‐foot room with single or multiple patients within the lobby was 1/2 mm Hg higher than awake ambulatory BP measurement in 422 patients and thus was an effective method.7 This separate empty room is not commonly available in most practices. It is unknown whether BP measured in a busy open waiting room lobby with other patients would accurately measure BP. The proper technique, including no talking, would need to be emphasized to the patient. In addition, the device would need to be secured to prevent theft. A retro‐construction of a “sitting waiting room” could be costly.

How much time does it take to measure BP and how much does it cost? I analyzed this by timing the measurement in my practice by either auscultation via a wall‐mounted (Tycos) device or by an automatic oscillometric device (Welch Allen Connex Vital Signs Monitor) that was programmed to measure BP during inflation, if possible, to save time. The auscultatory technique for 416 patients took an average of 58.6 ± 13.9 seconds (range, 15–146 seconds). The oscillometric technique was an average of 18.8 seconds faster (P < .05; 39.8 ± 23.0 seconds, range, 14–124 seconds); however, there was a user learning curve that improved with usage with the last third of the 411 patients, demonstrating an even faster average of 29.3 seconds per measurement. The average cost based on salary and benefits of the medical assistant in our practice was determined. For the auscultatory technique, it cost 35 cents per measurement. The automatic, oscillometric cost after the “learning curve” was 17 cents per measurement, or a savings of 17 cents per measurement. Although this does not appear to be a substantial savings, BP is measured for each PCP for every patient visit. If you assume 25.6 patient visits per day, 5 days per week for 52 weeks, as was performed in this study, the savings is $1119 per year. The BP measurements were 10/6 mm Hg higher with the oscillometric technique; however, the patient population was different with each technique and multiple factors could account for this difference.

How should BP be measured during the 331.2 million primary care visits? It is time to abandon the auscultatory method and switch completely to digital measurements. Validated digital machines that are designed for office use are preferred. The manufacturers of these devices should make them more affordable for the large number of primary care offices that could purchase these machines to increase sales. The measurements should be accurate, and I have found that the devices are not the culprit in errors, but rather the humans using them. The two most common errors—too small of cuff size and taking the measurement immediately upon sitting during conversation—could be easily corrected. Although it is preferred to sit alone in an examination or “vital signs” room, this is not likely to occur. If the readings are elevated, repeating the measurement by auscultation by the provider will often correct many falsely elevated readings. Out‐of‐office measurements should be the norm for diagnosis (24‐hour ambulatory BP monitoring) or treatment (validated home BP monitoring with the correct cuff size).

The technology to use home monitoring of BP with transmission and feedback from the provider to the patient is available in a piecemeal fashion. It is time to integrate and reimburse for this service while also measuring control rates in a practice or population. Validated BP monitors should be co‐purchased (50%) by insurance companies, every 5 years, and with proof of usage by the patient, making the 50% patient payment refundable. Healthcare Effectiveness Data and Information Set (HEDIS) measurement guidelines will need to be updated to reflect out‐of‐office measurements, which are clinically relevant data.

The American Society of Hypertension with the American Heart Association should together pledge support for expanding out‐of‐office BP measurements with reimbursement and work to change HEDIS to accept these measurements for improvement of the actual control of hypertension in primary care practices and populations—a remarkable value for society!

CONFLICTS OF INTEREST

The author has no conflicts of interest to declare.