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Department: INSPIRING CHANGE

Ensuring accurate BP measurements

Matheson, Emily DNP, CRNA, CCRN; Kremer, Michael PhD, CRNA, FAAN; Fogg, Louis PhD; Crisanti, Gia MSN, RN, ANP-BC, CNML

Author Information
doi: 10.1097/01.NURSE.0000657040.45768.02
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Abstract

ACCORDING TO THE CDC, 45% of US adults have hypertension or take BP medication. Hypertension increases the risk of heart disease and stroke. On average, treatment for hypertension costs around $55.9 billion each year and contributes to approximately 1,300 deaths every day.1 This article details a quality improvement project to promote increased compliance with standards set in 2005 by the American Heart Association (AHA) for measuring BP.2 At the time of this project, these were the most current guidelines, but the AHA updated them in 2019.3

Background

Although BP is one of the most important vital signs in healthcare settings, it is often measured inaccurately.2,4-8 The AHA techniques for obtaining accurate BP measurements served as the basis for the 10 specific guidelines described in this quality improvement project (see Assessing compliance with AHA guidelines).2,3

Nurses may not always follow all of the AHA guidelines regarding BP measurements, leading to inaccuracies, potentially unnecessary treatments, and decreased patient safety.2,5,9 For example, one study demonstrated that 97% of BP measurements failed to meet all of the AHA guidelines, and the wrong cuff size was used on 36% of patients.10 Another found that only 33.4% of BP measurements followed one-third of the recommended techniques, and none followed every guideline.11

Although AHA guidelines target outpatient clinics or provider offices, many principles can be applied in acute care settings as well. An informal assessment of BP cuff size accuracy in a cardiac ICU (CICU) at the authors' facility found that the correct cuff size was used on only 50% of patients.

For a BP cuff to be the correct size, the length of the cuff bladder should be 75% to 100% of the patient's arm circumference; similarly, the width should be 37% to 50% of the arm circumference.2,3,12 According to the AHA guidelines, patient arm circumference is “measured at the midpoint of the acromion and olecranon process.”3 Cuffs that are too small will give a falsely elevated result, while those that are too large will give a falsely low result.2,3,12,13

Proper patient positioning is also crucial for accurate BP measurements.2,4,12 The cuff should be positioned on the patient's upper arm and aligned level with the right atrium at approximately the midpoint of the sternum to reduce hydrostatic effects on the results.2,3 BP measurements change by 2 mm Hg for every inch the patient's arm is above or below the heart, making it imperative that the BP cuff is correctly aligned.2 For example, if the extremity is below the right atrium, the patient's systolic and diastolic pressures will be falsely elevated.2,4,12 If the extremity is above the right atrium, BP will be falsely low.2,4,12

Education improves compliance

A 2015 study found dramatic increases in staff compliance with AHA guidelines following the implementation of a 1-hour continuing-education program. The program included one-on-one teaching for 54 members of the healthcare staff and posting printouts of the guidelines in each patient's room. In an initial audit, 87% of the staff used an incorrect BP cuff size and 94% did not position the patient's arm level with the heart. After the intervention, 87% of the staff used the correct cuff size and 83% had positioned the arm correctly.14

In another study, 24 nurses were educated on AHA BP techniques and audited after their training.5 Although compliance increased after the intervention, only one area of the study showed 100% compliance: documenting the BP in the medical record. There was a 50% increase in use of a correct cuff size and a 12% increase in proper arm placement.5

In an Italian study, researchers surveyed a random sample of patients at 14 hospitals to assess staff compliance with specific guidelines for accurate BP measurement techniques.11 They completed 1,334 surveys related to 15 different BP guidelines, which demonstrated more than 70% compliance in nine of the practice areas. However, their research also demonstrated less than 20% compliance in measuring arm circumference to determine correct cuff size, checking BP in both arms, and measuring it only once.11

Another study examined barriers for clinic staff in performing accurate BP measurements. The investigators observed 54 patients in six different facilities. Clinic managers were then interviewed, and six focus groups were conducted with the healthcare staff. Common themes included staff knowledge and behavior, workflow, equipment and layout, and patient characteristics and behavior. The study concluded that multiple factors influenced the staff's ability to measure BP correctly.15

Purpose

This quality improvement project was implemented in a 28-bed CICU unit at the authors' hospital in Chicago, Ill. Its purpose was to improve patient safety by determining how frequently the staff followed AHA guidelines, identifying barriers to obtaining accurate BP measurements, and creating interventions to improve accuracy. It was completed with grants from the Center for Clinical Research and Scholarship and the Professional Nursing Staff, which is part of the shared governance at the authors' facility; these funds went toward purchasing laminated posters to post in patient rooms and place in bedside clinical reference binders.

The project was exempted by the Institutional Review Board, and no staff or patient consent was required. Participants consisted of CICU staff members, including nurses, nursing assistants, and patient-care technicians. Approximately 110 nurses worked on the unit at the time of this project. Those who participated did so voluntarily and without formal consent. No staff personal information or patient identifiers were used. Participants attended a short educational session with pre- and posttesting to assess their knowledge according to AHA guidelines.

The project had two specific aims:

  • a statistically significant improvement in at least 50% of the test questions
  • a 50% increase in the average number of AHA guidelines followed by staff after all the interventions were implemented.

Methods

One method to address inaccurate BP measurements is staff education about AHA guidelines. Educating the healthcare staff about correct techniques increases compliance. If more AHA guidelines were followed after the implementation of AHA interventions during this project, the interventions would be considered successful, potentially leading to more accurate BP measurements.

Poster reminders represent another way to address this issue, as it is unlikely that healthcare professionals will remember every AHA guideline. These were placed near patient monitors and in other areas to provide the staff with a handy reference tool (see BP poster reminders).

In the CICU, patient rooms were not initially stocked with every BP cuff size. Additionally, there was no standardized process for how they were supplied, making it difficult to know if the correct size would be available in a patient's room. A standardized process was developed to ensure that all BP cuff sizes would be available when needed.

The healthcare staff often used manual sphygmomanometers to monitor patient BP measurements when they were abnormal or dramatically different from previous readings and to check the accuracy of automated BP monitors. Unfortunately, many room sphygmomanometers were either broken or missing. During this project, operational sphygmomanometers were placed in each room to resolve this issue.

Interventions

The project lasted from April to September 2016, incorporating the following five interventions:

  • Short educational sessions were conducted to discuss AHA guidelines.
  • Poster reminders, including a summary of the guidelines, were placed in each patient's room. The same poster reminders were included in bedside clinical reference binders.
  • BP cuffs in multiple sizes were stocked in each room, and the process of restocking them was standardized.
  • Sphygmomanometers were repaired as needed and available in each patient's room.
Figure
Figure:
BP poster reminders2,3

An initial audit was completed to gauge staff compliance with the 10 selected AHA guidelines. Patients were excluded if the cuff had been placed anywhere other than the upper arm and if they had an arterial line because their BP measurements were not taken routinely by the staff. The principal investigator (PI) observed each BP measurement during the audit to maintain consistency. Only automatic BP readings using the oscillometric method were audited, as almost all BP measurements were obtained on the unit through this method rather than manually. The PI observed each BP measurement from outside the room without the knowledge of the nurse or patient, then the PI entered the room to assess compliance. Audit data were collected over several weeks, at different times, on varying days, and over multiple shifts to obtain an adequate sample size. Forty-six BP measurements were used in the initial audit.

The nurse manager then emailed the staff a link to an anonymous 9-question online pretest on the AHA guidelines and a survey regarding barriers to following them; 43 staff members completed the survey and 71 completed the pretest. Following the preliminary online components, focus groups of 1 to 10 participants were invited to attend short educational sessions hosted by the PI. More than 20 sessions were conducted, each lasting approximately 10 minutes.

Immediately after the educational sessions, a posttest was administered to gauge the level of knowledge gained from the intervention. It contained the nine questions included in the pretest and was completed by 72 participants. In an effort to reach as many staff members as possible, focus groups were conducted only by the PI over a period of several weeks, at varying times of the day, during different shifts, and on multiple days.

Physical reminders summarizing the AHA guidelines, such as small posters, were hung in all patient rooms. These were also included in the bedside clinical reference binders.

BP cuffs come in multiple sizes, but there is some variability among manufacturers.2,3 This study incorporated small adult (12 cm by 22 cm), adult (16 cm by 30 cm), adult long (16 cm by 30 cm), and large adult (16 cm by 36 cm) cuff sizes. The adult long BP cuff has the same bladder size as the adult cuff but a longer flap to wrap around the patient's arm. Although the adult long BP cuff is not included in the AHA guidelines, the authors decided to include it because it was used throughout the facility and a hospital-wide change would be required to stop using it.

Figure
Figure:
Initial and final audit results

One BP cuff of each size was stocked in the top drawer of the nightstand in every room. These sizes were chosen because they are most commonly used in the CICU. They were restocked by staff during room turnovers as part of the setup process. Similarly, all manual sphygmomanometers were repaired, and one was placed in each room to verify BP measurements as needed.

About 2 weeks after the interventions were implemented, the PI completed a final audit of BP measurements to determine staff compliance with the AHA guidelines. Using the same criteria from the initial audit, this process occurred over several weeks with 46 patient BP measurements assessed. Afterward, another survey was emailed to the staff by the nurse manager. It included the same questions as the initial survey, as well as additional questions related to the interventions; 39 staff members completed the final survey.

Outcomes

This project examined changes in nursing knowledge following the educational sessions, which was demonstrated through staff test scores, and compliance with AHA guidelines, which was determined through audits. Pre- and posttesting assessed staff knowledge before and after the educational sessions; initial and final audits evaluated staff compliance with AHA guidelines; and the initial and final surveys considered the barriers healthcare professionals face in taking accurate BP measurements, as well as any changes in these barriers after the interventions.

Data were obtained through the observational audits, surveys, and tests. Each audit was conducted by the PI for consistency and followed a key for each AHA guideline, resulting in quantitative data and demonstrating percent compliance with guidelines. The initial audit was compared with the final audit to determine the percentage of improvement in compliance.

Only multiple-choice questions were used in pre- and posttesting, with one correct answer for each question. The pretest results were compared with posttest results to determine the percent improvement in knowledge gained from the educational session. Each question was analyzed individually for percent improvement and statistical significance.

The initial survey questions focused on the perceived barriers to accurately measuring BP. These questions were repeated in the final survey to determine any reductions in these barriers. The final survey also included questions on the use of each intervention, as well as an overall reduction in barriers to accurate BP measurements. Each question featured scaled responses such as strongly agree, agree, disagree, and strongly disagree.

This project utilized the Statistical Package for the Social Sciences software for all statistical analyses.16 Descriptive statistics included mean, median, mode, average, percent, and frequency. Chi-square statistics, which measure deviations from chance in a contingency table, were used to assess statistical significance; a two-tailed alpha of .05, which represents the probability of rejecting the null hypothesis when it is true, was used as a criterion for significance. Improvement was analyzed by examining 2x2 contingency tables, meaning items considered correct or incorrect were crossed with the pre- and postintervention results.17

Results

In total, 72 staff members (65%) participated in the educational sessions, which exceeded the project goal of 50% participation. The initial and final audits each included 46 patients. In the initial audit, the staff followed an average of 5.20 of the 10 AHA guidelines, ranging from 2 to 10. In the final audit, the staff followed an average of 8.54 AHA guidelines, demonstrating a 60.9% increase and ranging from 5 to 10. (See Initial and final audit results.)

Eight of the 10 AHA guidelines examined during this project demonstrated improvement after the educational sessions. One guideline (placing the cuff directly on the patient's skin) remained at 100% in both audits, while another (patients should not speak during the reading) stayed consistent at 78%.

Correct BP cuff sizes were used 74% of the time in the initial audit and 94% of the time in the final audit. Initially, the lower edge of patient cuffs were correctly positioned at 2 to 3 cm above the antecubital fossa 26% of the time and improved to 80% of the time in the final audit. Similarly, 48% of patients were positioned correctly, either in the supine position or seated in the initial audit; 72% were correctly positioned in the final audit. BP cuffs were level with the right atrium of the heart approximately 17% of the time initially and 91% of the time in the final audit. They were also correctly aligned with the brachial artery 24% of the time initially compared with 70% in the final audit.

Table
Table:
Pre- and posttesting

Additionally, patients' backs were supported 67% of the time initially and 98% in the final audit. The arm with the BP cuff was still during the reading in 74% of patients during the initial audit and 91% of the time after the educational sessions. The arm was correctly supported 11% of the time in the initial audit and 80% of the time in the final audit.

One participating member of the healthcare staff joined an educational session after the pretest had been administered. As a result, 71 nurses took the pretest, while 72 took the posttest. The scores showed dramatic improvement in knowledge between the two, with six out of nine questions showing statistical significance. Each showed improvement with the exception of the fifth question regarding patients on their left side with the cuff on their right arm; this showed a slight, unexplained decrease. (See Pre- and posttesting.)

The initial survey had 43 participants, and the final survey had 39. Significant improvement was found in the extent to which the participating nurses were using the AHA guidelines. There was also a significant increase in the number of staff who agreed or strongly agreed that they had all of the necessary supplies at the bedside to take accurate BP measurements after the interventions (see Pre- and postsurvey responses).

Discussion

This quality improvement project demonstrated an overall increase in compliance with AHA guidelines among the participating nurses. Both specific aims were met. The first was accomplished with 66.7% of the test questions, or six of nine questions, showing statistical significance. The second was achieved with a 60.9% increase in the average number of AHA guidelines followed from the initial to the final audits (5.20 versus 8.54).

Table
Table:
Pre- and postsurvey responses

The final survey showed a statistically significant increase in the number of staff who believed they had all the necessary supplies to take accurate BP measurements at the bedside. All participants in the final survey agreed or strongly agreed that the educational sessions were presented effectively. They also agreed or strongly agreed that having different BP cuff sizes available in the room increased their ability to use the correct size with each patient. (See Postsurvey evaluations.)

Summary

The interventions used during this project improved compliance with the AHA guidelines and may be useful in other areas of practice. The educational focus group sessions helped improve staff knowledge of the AHA guidelines, with six out of nine areas demonstrating a statistically significant improvement. The poster reminders were available in both patient rooms and the bedside clinical reference binders. Additionally, by stocking BP cuffs of multiple sizes in each room, the staff was able to attain and place the correct cuff on patients without having to search for the correct size. Similarly, repairing all sphygmomanometers and placing one in each room provided another way to verify BP measurements if necessary.

Table
Table:
Postsurvey evaluations

Inaccurate BP measurements are a common, albeit underrecognized, issue in healthcare institutions. Because this project was implemented in the CICU at the authors' hospital, the interventions and results may not be applicable to other settings. Until the findings are replicated, it is unclear how effective the educational sessions will be in other units and practices. Barring evidence to the contrary, however, we have no reason to believe that this quality improvement project could not be incorporated with success in other settings.

Assessing compliance with AHA guidelines3

An initial audit was completed to gauge staff compliance with these 10 AHA guidelines:

  • correct cuff size
  • cuff applied directly to skin
  • cuff placement 2 to 3 cm above antecubital fossa
  • cuff aligned with brachial artery
  • patient is silent
  • patient is in supine or seated position
  • patient's arm is level with heart
  • patient's arm is still
  • patient's arm is supported
  • patient's back is supported.

These represent a small portion of the complete AHA guidelines and were chosen because they were the most realistic in terms of implementation and incorporation into the CICU workflow. The complete guidelines can be reviewed at

www.ahajournals.org/doi/full/10.1161/HYP.0000000000000087.

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    Keywords:

    AHA guidelines; American Heart Association guidelines; blood pressure measurement; hypertension

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