This section provides data for three consecutive blood pressure (BP) measurements and other methodological measurements to obtain an accurate BP. Heart rate or pulse, depending on age, are also reported.
BP is measured on participants 8 years and older; radial (or brachial, if necessary) pulse is measured on participants 8 years and older; and heart rate is measured on children 0-7 years of age.
Protocol and Procedure
After resting quietly in a seated position for 5 minutes and after the participant’s maximum inflation level (MIL) has been determined, three consecutive BP readings are obtained. If a BP measurement is interrupted or incomplete, a fourth attempt may be made. All BP determinations (systolic and diastolic) are taken in the mobile examination center (MEC). Participants with any of the following on both arms are excluded from the exam: rashes, gauze dressings, casts, edema, paralysis, tubes, open sores or wounds, withered arms, a-v shunts, and radical mastectomy. BP measurements are taken in the right arm unless specific conditions prohibit the use of the right arm, or, if participants report any reason that the BP measurements should not be taken in the right arm.
Prior to BP measurements, upper arm circumference is measured, which is done to guide selection of cuff size. Details on the protocol for obtaining upper arm circumference is described in the Physician Examination Procedures Manual. The following criteria were used to guide selection of cuff size:
||Bladder width (cm)
||Bladder length (cm)
Quality Assurance & Quality Control
The BP examiners are certified for BP measurement through a training program from Shared Care Research and Education Consulting. Certification is achieved when physician examiners meet all requirements of the training program. The initial training includes:
- Didactic instruction about BP measurement and propensity for error;
- Listening to systolic and diastolic BP sounds using a standardized audio-video presentation;
- An audio-video test;
- A written exam; and
- Simultaneously listening to BP on a minimum of 20 volunteers, of all ages, through a Y- stethoscope to compare measures with a gold standard instructor who does the same.
Certification requires a score of 100% on the audio-video test. Correct answers on the audio-video test require the examiner’s answers and the standardized test answers to be within +/- 2 mmHg (millimeter of mercury) on 92% of 24 measures (12 systolic, 12 diastolic), and within +/- 4 mmHg on 100% of 24 measures (12 systolic, 12 diastolic).
For more details on the procedures for measuring heart rate, pulse, and BP and for details related to quality assurance/quality control for this component, please refer to the Physician Examination Procedures Manual.
Data Processing and Editing
The following are some specifications used in capturing the BP data:
- Systolic BP and maximum inflation level cannot be greater than 300 mmHg;
- Systolic and diastolic BP measurements and the maximum inflation level can be even numbers only;
- Systolic blood pressure must be greater than diastolic BP;
- If there is no systolic BP, there can be no diastolic BP. (There can be a systolic measurement without a diastolic measurement.); and
- Diastolic BP can be zero.
The physicians attempting to obtain BP may enter comments related to reasons for incomplete data. This data is recorded in the BPX dataset as PEASCCT1. For this variable PEASCCT1=3, or “time constraints” was assigned if the recorded comment was either “no time” or “came late/left early.” PEASCCT1=4, or “other”, was assigned based on a variety of comments, including participant ill/emergency. There were no other recodes to this variable prior to data release.
Exam sample weights should be used for analyses. Please refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial for further details on the use of sample weights and other analytic issues.