Sidestream end-tidal carbon dioxide monitoring during helicopter transport

Performance of capnometry in non-intubated infants in the pediatric intensive care unit

Background

Assessing the ventilatory status of non-intubated infants in the Pediatric Intensive Care Unit (PICU) is a constant challenge. Methods to evaluate ventilation include arterial blood gas analysis (ABG), which is invasive and intermittent, and transcutaneous carbon dioxide monitoring (P_tcCO2), which, while non-invasive, is also intermittent. A method that is non-invasive and continuous would be of great benefit in this population. We hypothesized that non-invasive capnometry via sidestream monitoring of exhaled carbon dioxide (CO₂) would provide an acceptable measurement of ventilatory status when compared to ABG or P_tcCO2.

Methods

Preliminary prospective study of infants less than one year of age admitted to the PICU in a large urban teaching hospital. Infants not intubated and not requiring non-invasive ventilation were eligible. A sidestream CO₂ reading was obtained in a convenience sample of 39 patients. A simultaneous ABG was collected in those with an arterial catheter, and a P_tcCO2 was obtained in those without.

Results

Correlation of sidestream CO₂ with ABG was excellent (r² = 0.907). Sidestream correlated less well with P_tcCO2 (r² = 0.649). Results were not significantly altered when weight and respiratory rate were added as independent variables. Bland-Altman analysis revealed a bias of -2.7 with a precision of ±6.5 when comparing sidestream CO₂ to ABG, and a bias of -1.7 with a precision of ±9.9 when comparing sidestream CO₂ to P_tcCO2.

Conclusions

Performance of sidestream monitoring of exhaled CO₂ is acceptable clinical trending to assess the effectiveness of ventilation in non-intubated infants in the PICU.

Utility of initial prehospital end-tidal carbon dioxide measurements to predict poor outcomes in adult asthmatic patients

STUDY OBJECTIVE

To determine if an initial (before treatment) prehospital end-tidal carbon dioxide (EtCO2) measurement in adult, non-chronic obstructive pulmonary disease (COPD), asthmatic patients predicts patient outcomes.

METHODS

This is a retrospective chart review of EtCO2 assessment data in a convenience sample of adult, asthmatic patients transported via advanced life support (ALS) units to a large, urban, academic hospital. Initial EtCO2 measurements were obtained routinely on all respiratory distress patients in the field, and emergency department physicians were unaware of the results. Data were analyzed using descriptive statistics, including percentages, means, and 95% confidence intervals (CI).

RESULTS

We reviewed data for prehospital initial EtCO2 measurements on 299 unique asthma patients (repeat visits by same patient were not included). Mean (SD) age was 43.1 years (12.5) and 142 (47.5%) were male. The mean EtCO2 measurement was 38.8 mmHg (SD ± 9.5; CI: 37.7-39.9; range: 14-82). Examination of initial EtCO2 measurements by deciles revealed that extreme values, in the lowest (14-28 mmHg) and highest (50-82 mmHg) deciles, experienced more markers of poor outcome than less extreme measurements. Patients were thus dichotomized by extreme (n = 59) or nonextreme (n = 240) EtCO2 measurements. More extreme patients were ultimately intubated (30.5 vs. 5.8%; p < 0.001; positive predictive value (ppv) = 30.5% ), and/or admitted to the intensive care unit (ICU) (28.8 vs. 6.7%; p <0.001; ppv = 28.8%), and/or died (5.1 vs. 0%; p = 0.007 [Fisher's exact test]; ppv = 5.1%), than nonextreme patients, respectively.

CONCLUSION

Extreme (both low and high) prehospital initial EtCO2 measurements may be associated with markers of poor patient outcomes. Future work will prospectively determine whether the addition of this information improves early recognition of severe asthma episodes beyond clinical assessment.

Critical care transport of patients who have acute neurological emergencies

This article reviews the special questions and issues in critical care transport related specifically to the care of patients who have neurologic emergencies. It first considers potential indications for transport and reviews attempts to create a hierarchical stroke center system akin to that developed for trauma care. It then discusses therapeutic concerns relating to the transport environment and the use of specific interventions, including the effects of end-tidal CO(2) monitoring on intracranial pressure, patient outcomes after traumatic brain injury, and opportunities to initiate therapeutic hypothermia in comatose survivors of cardiac arrest during transport. Finally, the cost of critical care transport of patients who have neurologic emergencies is considered.