Blood pressure measurement in obese patients: non-invasive proximal forearm versus direct intra-arterial measurements

Background: In obesity, accurate perioperative blood pressure measurement using upper arm, non-invasive blood pressure (NIBP) is technically challenging. Proximal forearm NIBP may be an acceptable substitute. Mean arterial blood pressures (MAP) estimated by proximal forearm NIBP were compared with direct intra-arterial measurements. It was hypothesised that the measurement techniques would be interchangeable if between-technique MAP differed ≤ 20% and MAP ratios were < 1.2 and > 0.8. Method: A total of 30 adults with body mass index ≥ 30 kg/m2 in whom perioperative intra-arterial blood pressure measurement was considered mandatory were enrolled. MAP measurements using the two techniques were obtained at three random intervals in each patient. Bland­Altman analyses were employed. Results: Forearm mean NIBP MAP overestimated mean intra-arterial MAP by 2.2 (SD 8.1; range from 23.8 to ­19.4 mmHg; p = 0.011, 95% CI 3.9 to 0.5). However, Bland­Altman analyses revealed a wide dispersion with several MAP differences and MAP ratios exceeding the pre-specified bounds for interchangeability. Conclusion: Forearm NIBP could not be considered interchangeable with direct intra-arterial MAP measurements in obese patients