Abstract
Study Objective
To determine if the slope of Phase II and Phase III, and the alpha angle of the expiratory
capnographic waveform, as measured via computer-recognizable algorithms, can reflect
changes in bronchospasm in acute asthmatic non-intubated patients presenting to the
emergency department (ED).
Methods
In this prospective study carried out in a university hospital ED, 30 patients with
acute asthma were monitored with clinical severity scoring and peak flow measurements,
and then had a nasal cannula attached for sidestream sampling of expired carbon dioxide.
The capnographic waveform was recorded onto a personal computer card for analysis.
The patients were treated according to departmental protocols. After treatment, when
they had improved enough for discharge, a second set of results was obtained for capnographic
waveform recording. The pre-treatment and post-treatment results were then compared
with paired-samples t-test analysis.
Results
On the capnographic waveform pre- and post-treatment, there was a significant difference
in the slope of Phase III (p < 0.001) and alpha angle (p < 0.001), but not in the Phase II slope (p = 0.35). There was significant change in peak flow meter reading, but it was poorly
correlated with all the capnographic indices.
Conclusion
The study provides some preliminary data showing that capnographic waveform indices
can indicate improvement in airway diameter in acute asthmatics in the ED. Capnographic
waveform analysis presents several advantages in that it is effort-independent, and
provides continuous monitoring of normal tidal respiration. With further refined studies,
it may serve as a new method of monitoring non-intubated asthmatics in the ED.
Keywords
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Article info
Publication history
Published online: March 09, 2009
Accepted:
October 13,
2008
Received in revised form:
September 7,
2008
Received:
July 11,
2007
Identification
Copyright
© 2011 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
