Repeatability of SphygmoCor pulse wave analysis in assessing arterial wave reflection in pregnancy using applanation tonometry

Objective: To estimate clinical agreement in relation to measuring aortic augmentation index (AIX-75) in pregnancy in a routine clinical setting. Methods: A hospital-based clinical agreement study of 20 women in which two trained nurses alternated in measuring arterial function (AIX standardized to a heart rate of 75 beats-per-minute, AIX-75) on a single occasion in triplicate, after participants had rested semi-recumbent for 15 min. Right brachial blood pressure (BP) was measured using the Microlife 3BTO-A oscillometric device. Radial applanation pulse wave analysis (PWA) was undertaken according to current guidelines using the SphygmoCor device with a hand-held Millar tonometer applanated at the right radial artery. Each nurse was blinded to others PWA results. Observer agreement was assessed using the Bland-Altman "limits of agreement" (LOA, mean difference ±2 SD) approach. Results: Median gestation was 37 weeks (range: 12-42), mean age 31 years, 30% nulliparous, mean brachial BP 128/79 mm Hg. Based on all six PWA measurements, mean AIX-75 was 11.7 (range: -18 to +35). The between-observer LOA was 0.1 ± 11.0 and the within-observer LOA's were 1 ± 10 and -2 ± 8 for the two nurses. Observer differences did not vary systematically with the magnitude of AIX-75. Conclusion: AIX-75 can be measured by nurses using PWA in pregnancy with a high level of observer agreement.