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Utility of the Expiratory Capnogram in the Assessment of Bronchospasm
Journal article   Peer reviewed

Utility of the Expiratory Capnogram in the Assessment of Bronchospasm

Michael Yaron, Paul Padyk, Molly Hutsinpiller and Charles B Cairns
Annals of emergency medicine, v 28(4), pp 403-407
01 Oct 1996
DOI: https://doi.org/10.1016/S0196-0644(96)70005-7
PMID: 8839525
Featured in Collection :   UN Sustainable Development Goals @ Drexel

Abstract

Study objective: To determine whether the plateau phase of the expiratory capnogram (d CO 2/dt) can detect bronchospasm in adult asthma patients in the emergency department and to assess the correlation between d CO 2/dt and the peak expiratory flow rate (PEFR) in spontaneously breathing patients with asthma and in normal, healthy volunteers. Methods: We carried out a prospective, blinded study in a university hospital ED. Twenty adults (12 women) with acute asthma and 28 normal adult volunteers (15 women) breathed through the sampling probe of an end-tidal CO 2 monitor, and the expired CO 2 waveform was recorded. The d CO 2/dt of the plateau (alveolar) phase for five consecutive regular expirations was measured and a mean value calculated for each patient. The best of three PEFRs was determined. The PEFR and d CO 2/dt were also recorded after treatment of the asthmatic patients with inhaled β-agonists. Results: The mean±SD PEFR of the asthmatic subjects was 274±96 L/minute (57% of the predicted value), whereas that of the normal volunteers was 527±96 L/minute (103% of the predicted value) ( P<.001). The mean d CO 2/dt of the asthmatic subjects (.26±.06) was significantly steeper than that of the normal volunteers (.13±.06) ( P<.001). The d CO 2/dt was correlated with PEFR (r=.84, P<.001). In 18 asthmatic subjects the pretreatment and posttreatment percent predicted PEFRs were 58%±17% and 74%±17%, respectively ( P<.001), whereas the d CO 2/dt values were .27±.05 and .19±.07, respectively ( P<.005). Conclusion: The d CO 2/dt is an effort-independent, rapid, noninvasive measure that indicates significant bronchospasm in ED adult patients with asthma. The d CO 2/dt value is correlated with PEFR, an effort-dependent measure of airway obstruction. The change in d CO 2/dt with inhaled β-agonists may be useful in monitoring the therapy of acute asthma. [Yaron M, Padyk P, Hutsinpiller M, Cairns CB: Utility of the expiratory capnogram in the assessment of bronchospasm. Ann Emerg Med October 1996;28:403-407.

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