End tidal carbon dioxide monitoring in acute asthma: a prospective pilot study in emergency department patients

Background The peak expiratory flow rate (PEFR) is the gold standard for monitoring asthmatic patients. However, its measurement requires understanding and active participation. End tidal carbon dioxide (EtCO2) may be considered an accurate surrogate for PaCO2, a severity marker in acute asthma. We studied the use of EtCO2 as a monitoring tool in acute asthma. Patients and methods This was a prospective study that included consecutive patients admitted to our emergency department for acute asthma exacerbation. Data were collected at first medical contact (T0) and after 1 h of treatment (T60). The primary endpoint was the change in EtCO2; the secondary endpoints included changes in the EtCO2Q angle value, plateau T time, and change in EtCO2 values for the patients with a PEFR ratio less than 50% after treatment. Results Fifty-five patients were included and 36 waveforms were analysed. The mean age was 37 years and 26 (47%) were women. The median initial PEFR was 200 [interquartile range (IQR): 150–240]; the median EtCO2 at T0 and T60 was 35 (IQR: 30–38) and 34 (IQR: 29–37). There was no significant change in EtCO2 after treatment. There was no significant change in the Q angle and the T time after treatment. At T60, 20 (36%) patients had a PEFR ratio less than 50%. Change in EtCO2 from T60 to T0 was associated with a PEFR ratio less than 50%. Conclusion After 1 h of treatment, there was no significant change in EtCO2. A decrease in EtCO2 seems to be associated with a higher risk of PEFR ratio less than 50% after treatment. Correspondence to Jennifer Truchot, MD, Hopital Lariboisiere, 75010 Paris, France Tel: +33 149 956 391; fax: +33 149 959 049; e-mail: jennifer.truchot@aphp.fr Received February 26, 2018 Accepted June 24, 2018 Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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