Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study
Dublin Core
Title
Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study
Subject
Capnography, End-tidal CO2, Respiration, Acidemia, Vital signs
Description
Abstract
Background Capnography is a quantitative and reliable method of determining the ventilatory status of patients.
We describe the test characteristics of capnography obtained during Emergency Department triage for screening
acidemia.
Results We performed an observational, pilot study of adult patients presenting to Emergency Department (ED)
triage. The primary outcome was acidemia, as determined by the basic metabolic panel and/or blood gas during the
ED visit. Secondary outcomes include comparison of estimated and measured respiratory rates (RR), relationships
between end-tidal CO2 (EtCO2) and venous partial pressure of CO2, admission disposition, in-hospital mortality during
admission, and capnogram waveform analysis. A total of 100 adult ED encounters were included in the study and
acidemia (
HCO−
3
≤ 22mEq/L or pH < 7.35) was identified in 28 patients. The measured respiratory rate (20.3 ±
6.4 breaths/min) was significantly different from the estimated rate (18.4 ± 1.6 breaths/min), and its area under the
receiver operating curve (c-statistic) to predict acidemia was only 0.60 (95% CI 0.51–0.75, p=0.03). A low end-tidal CO2
(EtCO2<32 mmHg) had positive (LR+) and negative (LR−) likelihood ratios of 4.68 (95% CI 2.59–8.45) and 0.34 (95%
CI 0.19–0.61) for acidemia, respectively—corresponding to sensitivity 71.4% (95% CI 51.3–86.8) and specificity 84.7%
(95% CI 74.3–92.1). The c-statistic for EtCO2 was 0.849 (95% CI 0.76–0.94, p=0.00). Waveform analysis further revealed
characteristically abnormal capnograms that were associated with underlying pathophysiology.
Conclusions Capnography is a quantitative method of screening acidemia in patients and can be implemented
feasibly in Emergency Department triage as an adjunct to vital signs. While it was shown to have only modest ability
to predict acidemia, triage capnography has wide generalizability to screen other life-threatening disease processes
such as sepsis or can serve as an early indicator of clinical deterioration.
Keywords Capnography, End-tidal CO2, Respiration, Acidemia, Vital signs
Background Capnography is a quantitative and reliable method of determining the ventilatory status of patients.
We describe the test characteristics of capnography obtained during Emergency Department triage for screening
acidemia.
Results We performed an observational, pilot study of adult patients presenting to Emergency Department (ED)
triage. The primary outcome was acidemia, as determined by the basic metabolic panel and/or blood gas during the
ED visit. Secondary outcomes include comparison of estimated and measured respiratory rates (RR), relationships
between end-tidal CO2 (EtCO2) and venous partial pressure of CO2, admission disposition, in-hospital mortality during
admission, and capnogram waveform analysis. A total of 100 adult ED encounters were included in the study and
acidemia (
HCO−
3
≤ 22mEq/L or pH < 7.35) was identified in 28 patients. The measured respiratory rate (20.3 ±
6.4 breaths/min) was significantly different from the estimated rate (18.4 ± 1.6 breaths/min), and its area under the
receiver operating curve (c-statistic) to predict acidemia was only 0.60 (95% CI 0.51–0.75, p=0.03). A low end-tidal CO2
(EtCO2<32 mmHg) had positive (LR+) and negative (LR−) likelihood ratios of 4.68 (95% CI 2.59–8.45) and 0.34 (95%
CI 0.19–0.61) for acidemia, respectively—corresponding to sensitivity 71.4% (95% CI 51.3–86.8) and specificity 84.7%
(95% CI 74.3–92.1). The c-statistic for EtCO2 was 0.849 (95% CI 0.76–0.94, p=0.00). Waveform analysis further revealed
characteristically abnormal capnograms that were associated with underlying pathophysiology.
Conclusions Capnography is a quantitative method of screening acidemia in patients and can be implemented
feasibly in Emergency Department triage as an adjunct to vital signs. While it was shown to have only modest ability
to predict acidemia, triage capnography has wide generalizability to screen other life-threatening disease processes
such as sepsis or can serve as an early indicator of clinical deterioration.
Keywords Capnography, End-tidal CO2, Respiration, Acidemia, Vital signs
Creator
Paul Peng1* and Alex F. Manini2
Source
https://doi.org/10.1186/s12245-024-00631-3
Date
2024
Contributor
Peri Irawan
Format
pdf
Language
english
Type
text
Files
Collection
Citation
Paul Peng1* and Alex F. Manini2, “Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study,” Repository Horizon University Indonesia, accessed April 11, 2026, https://repository.horizon.ac.id/items/show/12339.