Blood Pressure Measurement Site in Babies
Blood pressure should be measured in the right upper arm in babies, using an appropriately sized cuff with oscillometric technique in the outpatient setting. 1
Recommended Measurement Site
The right arm is the standard site for blood pressure measurement in infants and neonates for consistency, comparison with normative tables, and to avoid falsely low readings that could occur with left arm measurement in cases of coarctation of the aorta. 1
The American Heart Association and American Academy of Pediatrics both specify the right arm as the preferred location unless atypical aortic arch anatomy is present (such as right aortic arch with coarctation or left aortic arch with aberrant right subclavian artery). 1
Research confirms that the upper arm is the most accurate and least variable location for oscillometric blood pressure measurement in neonates, compared to alternative sites like the forearm or calf. 2
Alternative Sites and Their Limitations
Calf measurements can be obtained and typically show values nearly identical to arm measurements when the same-sized cuff is used, with mean differences of only 1.1 mm Hg systolic between arm and calf. 3
However, calf measurements should be reserved for specific clinical scenarios (such as screening for coarctation) rather than routine monitoring, as the upper arm remains the gold standard. 3, 2
Forearm measurements are less accurate than upper arm measurements and should be avoided for routine blood pressure assessment in neonates. 2
Critical Cuff Sizing Requirements
For neonates, the cuff bladder width should be 0.45 to 0.55 times the arm circumference (width-to-arm circumference ratio), with the bladder length encircling 80% to 100% of the arm circumference. 1
Visual assessment of cuff size (the "2/3 rule") is unreliable, with accuracy rates as low as 43-56% depending on the method used, making objective measurement of arm circumference essential. 4
Specific cuff sizes recommended by the American Heart Association include: newborn-premature infants (4×8 cm) and infants (6×12 cm). 1
Measurement Technique Considerations
Oscillometric technique is the standard method in office settings for neonates until the infant can cooperate with manual auscultatory measurement. 1
The oscillometric device must be validated for use in neonates and programmed with an initial inflation value appropriate for infants (generally ≤120 mm Hg). 1
The arm should be positioned at heart level, supported, and uncovered above the cuff during measurement. 1
Important Clinical Pitfalls
Incorrect cuff size is the most common source of error, with undercuffing (too small) producing falsely elevated readings and overcuffing (too large) producing falsely low readings, though the magnitude of error is smaller with overcuffing. 5
Oscillometric measurements tend to overestimate systolic blood pressure compared to intra-arterial measurements, particularly in neonates, and are less accurate when mean arterial pressure is below 30 mm Hg. 2, 6
The infant's activity state significantly affects readings, with active neonates showing values 6-10 mm Hg higher than quiet neonates, emphasizing the need for measurement in a calm state. 3
Blood pressure values increase rapidly in the first months of life, from approximately 78/47 mm Hg at 2-3 weeks to 95/60 mm Hg at 1-5 months, so age-appropriate normative values must be used for interpretation. 7