Analysis of physician ability in the measurement of pulsus paradoxus by sphygmomanometry

Context: Measurement of pulsus paradoxus (PP) is one of several measures previously advocated in the National Heart, Lung, and Blood Institute asthma management guidelines: a pulsus of > 12 mm Hg warranted hospital admission. It is one of only a few measures that is not effort dependent and therefore important in the evaluation of patients with asthma. Objective: Determination of physician accuracy in measuring PP. Design: A model of induced PP in a trained healthy subject without respiratory disease was constructed with a fixed inspiratory resistance with measurement of inspiratory air pressure and beat-to-beat BP noninvasively, Setting: Laboratory. Participants: Attending physicians from emergency medicine and critical care disciplines who served as consecutive examiners of the trained reference subject generating known PP. Interventions: A total of 19 attending physicians were assessed for ability in measuring PP by sphygmomanometry and by palpation. The reference subject generated 4 degrees of PP sequentially, with each examiner blinded to the value of negative inspiratory pressure and PP, Examiners first assessed PP qualitatively by palpation, followed by its measurement within 2 min. Main outcome measure: Proximity of physician-measured PP (PPm) to true PP (PPt). Results: At inspiratory pressures of -10, -15, -20, and -25 mm Hg, PPt was 13.7, 16.2, 19.1, and 20.7 mm Hg, respectively (F = 14.8, p < 0.0001; analysis of variance [ANOVA]). At the same pressures, PPm was 13.1, 17.5, 17.7, and 18.0 mm Hg (p > 0.10; ANOVA). Linear regression of PPm against PPt for each examiner revealed a slope (SE) of 0.53 (0.23), and not a 1:1 relationship. Conclusions: Past and present guidelines do not account for the challenges in measuring PP, especially in tachypneic patients. Sphygmomanometric determination of PP should be augmented by new aids developed through technological innovation.