Knowledge of accurate blood pressure measurement procedures in chiropractic students

Cardiovascular disease is the leading cause of mortality in the United States. The American Heart Association reported in 2003 that over 65 million Americans suffer from hypertension.¹  With the increasing demand for evidence-based chiropractic care and the effect of chiropractic manipulation on patients with hypertension reported by Bakris et al.,²  it is imperative that all chiropractic students be well-versed in the correct method for assessing blood pressures. This is in harmony with the Council on Chiropractic Education accreditation standards meta-competency 1 to perform properly an initial assessment and diagnosis of the patient.³  The accurate measurement of blood pressures by chiropractic students is assumed upon completion of this area of study in their education. Currently, chiropractic students in our college learn how to measure blood pressure during the beginning of their 1st year of training. Their proficiency is tested at the end of the 1st quarter.

Blood pressure measurement is a basic clinical procedure. However, numerous studies have shown that many errors are made from the incorrect performance of procedures.⁴  Observation of other health professions' literature suggests that measurement techniques may be out of line with current recommendations in various health care fields.^4–9  For example, one study showed that many physicians did not have the patient rest at least 5 minutes before the blood pressure measurement,⁵  and another showed that few physicians, if any, followed the American Heart Association guidelines when measuring blood pressure.^6,7  A final report showed that physicians used improper cuff sizes.⁸  Although to our knowledge there have been no studies of the blood pressure assessment skills of chiropractic students, we have postulated that the skills of chiropractic students would be no different from those of other health care professionals. Some of the many technical errors include using the wrong cuff size, or improper patient or arm positioning.¹⁰  We used a knowledge test of skills to assess the current knowledge of our chiropractic students.^11,12 

The knowledge test of blood pressure measurement skills was developed from a questionnaire crafted by the Wisconsin Heart Disease and Stroke Prevention Program¹²  and from a survey instrument developed for nurses in Australia,¹³  both of which were based on the American Heart Association 2005 guidelines.¹⁴  The test items were piloted on a small group of 2nd year chiropractic students. The finalized test included demographic and educational questions. Before answering the 16 test items, participants were asked to indicate on a Likert-type scale their level of confidence in the adequacy of their skills for accurate blood pressure measurement. The full survey is available online as a supplemental Appendix to this article.

Approval by our college institutional review board was obtained before conducting this research. A convenience sample was taken from 1st, 2nd, 3rd, and 4th year chiropractic students at the Palmer College of Chiropractic Florida campus. We independently processed the information collected from the questionnaire. The maximum attainable knowledge score was 16. A one-way ANOVA using SPSS 15.0 (SPSS Inc, Chicago, IL) was used to test for significant differences among the four groups. Levene's test of homogeneity of variance was used to verify whether the four groups' variances were equal or not. The test–retest method was used to see if there was internal consistency.

A total of 186 students participated in the study, constituting 68% of the total student enrollment (n = 274) at our college during the period of the study. Demographic data can be seen in Table 1. Of the 186 students participating in the study, 80% were confident about their knowledge of blood pressure measurement skills (agreed or strongly agreed), 15% were unsure, and 5% were not confident about their knowledge (Table 2). The mean score was 52% with a range of 24% to 88%. Table 3 shows a detailed breakdown of how the students performed on each of the questions in the test. Levene's test of homogeneity of variance was used to verify whether the four group variances were equal. The results did not show significant differences (p > .05), indicating that the four groups in the study could be considered equal. The one-way ANOVA showed statistically significant differences in the years 3 and 4 groups (Table 4). The distribution of the scores for individual items for the four groups of participants varied from item to item, showing a decay in knowledge when compared to years 1 and 2. There were no significant differences between the overall scores of the 1st, 2nd, 3rd, and 4th year students. Of the 16 questions given, the mean scores for 1st, 2nd, 3rd, and 4th year students were 10.4, 9.7, 7.9, and 8.33, respectively (Table 5). The decay in the knowledge between the 1st and 2nd year students was not statistically significant. There was a statistically significant decrease between the 1st two years and the latter two years (p < .005). Of the 16 knowledge areas tested in the blood pressure measurement skills test, 11 areas were of major concern (test item score <70%). Table 6 shows a summary of 7 of the above errors, and the degree of magnitude of the discrepancy of the resulting systolic and diastolic blood pressure recordings.

Several items are worthy of discussion, presented below with regard to deficiencies noted in test results and significance of these deficiencies.

Measuring the blood pressure with the patient sitting on the examination table could result in a higher blood pressure reading, since the patient's arm often is not at the level of the heart on the height of the table. Of the participants in the study 31% had difficulty recognizing this. Some participants thought that the forearm need not be supported with the palm facing up. A smaller number felt that it was wrong to have the patient's back against the chair with the feet flat on the floor.

Only 18% of the participants were aware of how the terminal reading should be recorded correctly. It is recommended by the American Heart Association that the recording should be to the nearest 2 mm Hg when using the mercury and aneroid sphygmomanometers to compensate for rapid and slow heartbeats.¹⁴ 

Not many of the participants were aware of the need to have the patient seated properly in a chair with back support and with both feet flat on the ground. Van Velthoven et al. found that sitting with the back unsupported and with the legs crossed will result in an erroneously high blood pressure.¹⁶  If the back is not supported, such as with the patient seated on the examination table, the diastolic pressure may be raised by as much as 6 mm Hg. Crossing of the legs will increase the systolic pressure by 2 to 8 mm Hg.

Ideally, the arm should be placed on a level with the patient's heart. Placing the arm lower than the level of the heart will result in a higher measurement, while placing it above the level of the heart will result in a lower measurement. Netea et al. reported that for each 5 cm change in arm position relative to the heart there was a corresponding change in blood pressure by 3 to 4 mm Hg.¹⁵ 

Using an inappropriate cuff size will result in an incorrect blood pressure result, which is something that 55% of the participants did not know. The length and width of the bladder within the blood pressure cuff should be at least 80% and 40% of the circumference of the patient's arm, respectively. Too small a cuff will result in a higher measurement.

Of the students, 49% were unfamiliar with how to avoid the auscultatory gap. The auscultatory gap is a phenomenon that may occur in some patients with very high blood pressures. In this phenomenon, the first Korotkoff sounds may appear, for example, at 220 mm Hg. As the cuff is deflated at the recommended 2 to 3 mm Hg per second rate, the blood pressure sound will disappear in some patients only to reappear at a lower blood pressure, perhaps at 180 mm Hg. If the systolic blood pressure was not determined initially by palpation, one is likely not to inflate the cuff as high as 240 mm Hg (palpatory systolic pressure plus 20 to 30 mm Hg). The patient would appear to have a systolic pressure much lower than that it actually is.

The bell of the stethoscope generally is recommended when measuring blood pressure and 49% of the participants were unaware of this. This may be a minor issue, however, as recent studies have indicated that there is no statistically significant difference when using the bell or the diaphragm.¹⁷ 

It is recommended that Korotkoff Phase V (when the sounds disappear completely) sounds be used when measuring the diastolic blood pressure. Phase IV sounds should be used only if the level of the Korotkoff Phase V sounds is greater than 10 mm Hg above the Korotkoff Phase IV level.

Our study has shown that our students possess an inadequate level of knowledge regarding the correct procedures for measuring blood pressure. This is not surprising given similar deficiencies in medical, nursing, and pharmacy students worldwide, as shown in Table 7.^9,10,18  If chiropractors are going to be involved in the global fight of reducing the risk of hypertension, then it is imperative that they improve their knowledge of how blood pressure measurements should be done. Although blood pressure assessment procedures may be simplified in the future by the increasing use of automatic devices, it does not mean that healthcare professionals can stop paying attention to factors, such as the position of the patient, the use of the correct cuff size, being seated with uncrossed legs in a chair with a back support, having rested five minutes before the measurement was taken, and not talking while the blood pressure is being measured.

There was a statistically significant difference between the mean scores of year 1/year 2 students and year 3/year 4 students (p < .05). This significant decay in blood pressure skills knowledge could be attributed to the fact that there has been no interval retraining of the students in the performance of this skill. In fact, 37% of the students surveyed were not aware of the American Heart Association recommendation that health professionals should be retrained every six months.¹  The reason for this recommendation is because of the rapid degradation of the skill that occurs after the initial training period. The six-month period has been determined by federally-funded multisite clinical trials of hypertension care and control.¹⁴  Limitations to this study include the need for a larger sample size over a longer period of time, as well as the psychometrics being unknown. A more accurate estimation of student knowledge of blood pressure measurement assessment clearly would be direct observation of them assessing blood pressure. Further research is needed for a more accurate conclusions.

Our study has found the knowledge of blood pressure skills of a sample of chiropractic students to be deficient. However, similar deficiencies have been noted in medical, nursing, and pharmacy students. There is a need for improved knowledge in assessing blood pressure measurement. We recommend that blood pressure measurement be taught in the 1st year and retraining should occur every six months, as recommended by the American Heart Association.¹  In addition, the use of a standardized checklist¹¹  would facilitate consistency among the trainers and observers of the skill.

The authors thank Dr Nui Zhang, MD for her invaluable help in analyzing the data and all of the students who participated in this study, as well as the course directors who kindly allowed us to use their class time to conduct the survey.

The authors have no conflicts of interest to declare.