CONTINUOUS, NONINVASIVE MEASUREMENT OF PULSUS PARADOXUS IN PATIENTS WITH ACUTE ASTHMA

Objective: To evaluate a continuous, noninvasive measurement technique for pulsus paradoxus (PP) as an objective asthma severity indicator. Design: Prospective, masked assessment of the relationship between PP, peak expiratory flow rate, oxygen saturation, clinical scoring, and a dmission decisions. Setting: An urban pediatric emergency department. Patients: Children with acute asthma. Interventions: Standardized trea tment per National Heart, Lung, and Blood Institute guidelines. Main O utcome Measures: Peak expiratory flow rate, oxygen saturation, pulmona ry index score, and masked disposition decision. Results: Significant positive correlations existed between PP and the pulmonary index score at the initial evaluation (r=0.44; P<.001) and after 30 minutes (r=0. 51; P<.001) and 60 minutes (r=0.45; P<.001). Significant negative corr elations existed between PP and the percent predicted peak expiratory flow rate (r=-0.31; P=.01) and the oxygen saturation (r=-0.30; P=.02). The mean PP was significantly greater in patients who were admitted f or further treatment at all time points (P=.003 or P=.002). At 30 minu tes after presentation, a PP greater than 15 mm Hg predicted admission for further treatment or relapse; the sensitivity was 0.42, the speci ficity was 0.89, and the likelihood ratio was 3.86.Conclusions: Our me asurement technique for PP is a useful objective indicator of the seve rity of asthma. Pulsus paradoxus correlates with clinical score, peak expiratory flow rate, and oxygen saturation. Furthermore, an elevated PP is associated with the decision to admit a patient for further trea tment. These results suggest that this technique may represent a usefu l research tool for the assessment of acute, severe asthma. Further de velopment of the technology may allow for a clinical application.