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
BP is measured on participants 8 years and older; radial (or brachial, if
necessary) pulse is measured on participants 5 years and older; and heart rate
is measured on children 0-4 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 were excluded from
the exam: rashes, gauze dressings, casts, edema, paralysis, tubes, open sores
or wounds, withered arms, a-v shunts, radical mastectomy. Participants were
also excluded if the BP cuff does not fit on the arm. 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 (see link provided below). 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 tape presentation;
- An audio-video tape 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 tape test. Correct answers on the audio-video tape test require the examiner’s answers and the standardized test answers to be within +/- 2mm of mercury (Hg) on 92% of 24 measures (12 systolic, 12 diastolic), and within +/- 4mmHg 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 located on the NHANES website.
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.
Changes Since 2015-2016:
Discontinued Items: PEASCST1, PEASCTM1
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.