Christopher L. Hunter

End-tidal carbon dioxide is associated with mortality and lactate in patients with suspected sepsis.

OBJECTIVE Exhaled end-tidal carbon dioxide (ETCO(2)) concentration is associated with lactate levels in febrile patients. We assessed the association of ETCO(2) with mortality and lactate levels in patients with suspected sepsis. METHODS This was a prospective observational study. We enrolled 201 adult patients presenting with suspected infection and 2 or more systemic inflammatory response syndrome criteria. Lactate and ETCO(2) were measured and analyzed with patient outcomes. RESULTS The area under the receiver operator characteristics curve (AUC) was 0.75 (confidence interval [CI], 0.65-0.86) for lactate and mortality and 0.73 (CI, 0.61-0.84) for ETCO(2) and mortality. When analyzed across the different categories of sepsis, the AUCs for lactate and mortality were 0.61 (CI, 0.36-0.87) for sepsis, 0.69 (CI, 0.48-0.89) for severe sepsis, and 0.74 (CI, 0.55-0.93) for septic shock. The AUCs for ETCO(2) and mortality were 0.60 (CI, 0.37-0.83) for sepsis, 0.67 (CI, 0.46-0.88) for severe sepsis, and 0.78 (CI, 0.59-0.96) for septic shock. There was a significant inverse relationship between ETCO(2) and lactate in all categories, with correlation coefficients of -0.421 (P < .001) in the sepsis group, -0.597 (P < .001) in the severe sepsis group, and -0.482 (P = .011), respectively. Adjusted odds ratios were calculated, demonstrating 3 significant predictors of mortality: use of vasopressors 16.4 (95% CI, 1.80-149.2), mechanical ventilation 16.4 (95% CI, 3.13-85.9), and abnormal ETCO(2) levels 6.48 (95% CI, 1.06-39.54). CONCLUSIONS We observed a significant association between ETCO(2) concentration and in-hospital mortality in emergency department patients with suspected sepsis across a range of disease severity.

Endotracheal tube placement confirmation: 100% sensitivity and specificity with sustained four-phase capnographic waveforms in a cadaveric experimental model

BACKGROUND Waveform capnography is considered the gold standard for verification of proper endotracheal tube placement, but current guidelines caution that it is unreliable in low-perfusion states such as cardiac arrest. Recent case reports found that long-deceased cadavers can produce capnographic waveforms. The purpose of this study was to determine the predictive value of waveform capnography for endotracheal tube placement verification and detection of misplacement using a cadaveric experimental model. METHODS We conducted a controlled experiment with two intubated cadavers. Tubes were placed within the trachea, esophagus, and hypopharynx utilizing video laryngoscopy. We recorded observations of capnographic waveforms and quantitative end-tidal carbon dioxide (ETCO2) values during tracheal versus extratracheal (i.e., esophageal and hypopharyngeal) ventilations. RESULTS 106 and 89 tracheal ventilations delivered to cadavers one and two, respectively (n=195) all produced characteristic alveolar waveforms (positive) with ETCO2 values ranging 2-113mmHg. 42 esophageal ventilations (36 to cadaver one and 6 to cadaver two), and 6 hypopharyngeal ventilations (4 to cadaver one and 2 to cadaver two) all resulted in non-alveolar waveforms (negative) with ETCO2 values of 0mmHg. Esophageal and hypopharyngeal measurements were categorized as extratracheal (n=48). A binary classification test showed no false negatives or false positives, indicating 100% sensitivity (NPV 1.0, 95%CI 0.98-1.00) and 100% specificity (PPV 1.0, 95%CI 0.93-1.00). CONCLUSION Though current guidelines question the reliability of waveform capnography for verifying endotracheal tube location during low-perfusion states such as cardiac arrest, our findings suggest that it is highly sensitive and specific.

Prehospital End-tidal Carbon Dioxide Predicts Mortality in Trauma Patients

Abstract Background: End-tidal carbon dioxide (EtCO2) measurement has been shown to have prognostic value in acute trauma. Objective: Evaluate the association of prehospital EtCO2 and in-hospital mortality in trauma patients and to assess its prognostic value when compared to traditional vital signs. Methods: Retrospective, cross-sectional study of patients transported by a single EMS agency to a level one trauma center. We evaluated initial out-of-hospital vital signs documented by EMS personnel including EtCO2, respiratory rate (RR), systolic BP (SBP), diastolic BP (DBP), pulse (P), and oxygen saturation (O2) and hospital data. The main outcome measure was mortality. Results: 135 trauma patients were included; 9 (7%) did not survive. The mean age of patients was 40 (SD17) [Range 16–89], 97 (72%) were male, 76 (56%) were admitted to the hospital and 15 (11%) went to the ICU. The mean EtCO2 level was 18 mmHg (95%CI 9–28) [Range 5–41] in non-survivors compared to 34 mmHg (95%CI 32–35) [Range 11–51] in survivors. The area under the ROC curve (AUC) for EtCO2 in predicting mortality was 0.84 (0.67–1.00) (p = 0.001), RR was 0.82 (0.63–1.00), SBP was 0.72 (0.49–0.96), DBP was 0.72 (0.47–0.97), pulse was 0.51 (0.26–0.76), and O2 was 0.64 (0.37–0.91). Cut-off values at 30 mmHg yielded sensitivity = 89% (51–99), specificity = 68% (59–76), PPV = 13% (6–24) and NPV = 99% (93–100) for predicting mortality. There was no correlation between RR and EtCO2 (correlation 0.16; p = 0.06). Conclusion: We found an inverse association between prehospital EtCO2 and mortality. This has implications for improving triage and assisting EMS in directing patients to an appropriate trauma center.

Comparing Quick Sequential Organ Failure Assessment Scores to End-tidal Carbon Dioxide as Mortality Predictors in Prehospital Patients with Suspected Sepsis

Introduction Early identification of sepsis significantly improves outcomes, suggesting a role for prehospital screening. An end-tidal carbon dioxide (ETCO2) value ≤ 25 mmHg predicts mortality and severe sepsis when used as part of a prehospital screening tool. Recently, the Quick Sequential Organ Failure Assessment (qSOFA) score was also derived as a tool for predicting poor outcomes in potentially septic patients. Methods We conducted a retrospective cohort study among patients transported by emergency medical services to compare the use of ETCO2 ≤ 25 mmHg with qSOFA score of ≥ 2 as a predictor of mortality or diagnosis of severe sepsis in prehospital patients with suspected sepsis. Results By comparison of receiver operator characteristic curves, ETCO2 had a higher discriminatory power to predict mortality, sepsis, and severe sepsis than qSOFA. Conclusion Both non-invasive measures were easily obtainable by prehospital personnel, with ETCO2 performing slightly better as an outcome predictor.

Prehospital end-tidal carbon dioxide differentiates between cardiac and obstructive causes of dyspnoea

Background Differentiating between cardiac and obstructive causes for dyspnoea is essential for proper management, but is difficult in the prehospital setting. Objective To assess if prehospital levels of end-tidal carbon dioxide (ETCO2) differed in obstructive compared to cardiac causes of dyspnoea, and could suggest one diagnosis over the other. Methods We conducted a retrospective cohort study among patients transported by emergency medical services during a 29-month period who were diagnosed with either obstructive pulmonary disease or congestive heart failure (CHF) by ICD-9 codes. Initial prehospital vital signs, including ETCO2, were recorded. Records were linked by manual archiving of emergency medical services and hospital data. Results There were 106 patients with a diagnosis of obstructive or cardiac causes of dyspnoea that had prehospital ETCO2 levels measured during the study period. ETCO2 was significantly lower in patients diagnosed with CHF (31 mm Hg 95% CI 27 to 35) versus obstructive pulmonary disease (39 mm Hg 95% CI 35 to 42; p<0.001). Lower ETCO2 levels predicted CHF, with an area under the Receiver Operating Characteristics Curve of 0.70 (95% CI 0.60 to 0.81). Using ETCO2 <40 mm Hg as a cut-off, the sensitivity for predicting heart failure was 93% (95% CI 88% to 98%), the specificity was 43% (95% CI 33% to 52%), the positive predictive value was 38% (95% CI 29% to 48%), and the negative predictive value was 94% (95% CI 89% to 99%). Conclusions Lower levels of ETCO2 were associated with CHF, and may serve as an objective diagnostic adjunct to predict this cause of dyspnoea in the prehospital setting.