Capnographic Monitoring for Acute Asthma in the Emergency Department Setting

ABSTRACT

BACKGROUND: The capnographic curve indices, such as the slope of expiratory upstroke or alveolar plateau quantified by using the waveform of the capnogram, are correlated with obstructive airway disease. Some studies also have shown good correlations between these indices and FEV1 or PEFR, which are objective measurements for the classification of severity in asthma. We performed this study to suggest the feasibility of using expiratory capnography for monitoring asthmatic subjects in emergency departments(ED). METHODS: One hundred adult patients diagnosed with bronchial asthma were enrolled in this study. Using main-stream-type capnography(ULTRA CAP, Nellcor, USA), the angles alpha and Q on the capnographic trace were measured; then, the slope of expiratory upstroke(S1) was calculated. Patients were allocated by using the classifying severity of asthma exacerbation of the National Asthma Education and Prevention Program(NAEPP), and the capnographic indices were compared. A measured values of the angle Q for all patients were classified into 3 categories by the percentile; then, the correlation between the category of the angle Q and the classifying severity was analyzed. RESULTS: There were significant differences in the angle Q according to the severity of the asthma. Also, there was a significant correlation between the category of the angle Q and the classifying severity of asthma exacerbation. CONCLUSION: This study suggests that expiratory capnography would be a useful monitoring technique for adult asthmatic patients and for the triage of asthmatic patients in an ED setting, provided the capnographic indices are measured as rapidly as possible. Therefore, we look forward to the development of a computerized analysis program for easy measurement and quantification of capnographic indices.