Diagnostic utility of capnography in emergency department triage for screening acidemia: a pilot study

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 ([Formula: see text] or [Formula: see text]) 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.

Elevation of end-tidal CO2 during exercise is attenuated in patients with cardiac amyloidosis

Reduced exercise tolerance is one of the hallmarks of patients with cardiac amyloidosis (CA), but detailed biological responses during exercise were not investigated. The purpose of this study was to compare the cardiopulmonary exercise test (CPX) parameters between CA patients and propensity-matched heart failure patients. This was a single-center, retrospective, observational study of patients diagnosed with CA. The control group was extracted by propensity score matching from patients who underwent CPX for chronic heart failure during the same period. Clinical data including assessment of biological responses during CPX were compared between the patients with CA (CA group, n = 16) and the control group (non-CA group, n = 16). Echocardiography suggested more impaired diastolic function in the CA group than in the non-CA group. There was no significant difference between groups in the fraction of end-tidal carbon dioxide (FETCO2) at rest. However, the difference between the FETCO2 at rest and the FETCO2 at the respiratory compensation point (ΔFETCO2) was significantly smaller in the CA group than in the non-CA group (0.40% ± 0.37% vs. 0.82% ± 0.33%; p = 0.002). Only in the CA group, there was a significant negative correlation between the ΔFETCO2 and the E/e' ratio on echocardiography (r = - 0.521; p = 0.039) and the serum high-sensitivity troponin T concentration (r = - 0.501; p = 0.048). In conclusion, patients with CA may find it difficult to increase cardiac output during exercise due to severe diastolic dysfunction.

Sports despite masks: no negative effects of FFP2 face masks on cardiopulmonary exercise capacity in children

Face masks were recognized as one of the most effective ways to prevent the spread of the COVID-19 virus in adults. These benefits were extended to children and adolescents. However, the fear of negative consequences from wearing a face mask during physical exercise led to cancellations of physical education lessons. This further decreased the amount of physical activity available to children and adolescents during the pandemic. However, there is little published data on the potential adverse effects of wearing the most effective and partially mandatory FFP2/N95 face masks during PE or physical activity (PA) in this age. Even though the pandemic has been declared as passed by the WHO, the rise of a new pandemic and thus the use of face masks for limiting its spread is inevitable, so we need to be better prepared for alternative options to lockdown and limitation of PA in such a scenario. Twenty healthy children aged 8-10 years performed two identical cardiopulmonary exercise tests as an incremental step test on a treadmill within an interval of 2 weeks, one time without wearing a protective mask and one time wearing an FFP2 mask. The cardiopulmonary exercise parameter and especially the end-expiratory gas exchange for oxygen and carbon dioxide (petO2 and petCO2) were documented for each step, at rest and 1 min after reaching physical exhaustion. Twelve boys (mean age 8.5 ± 1.4 years) and 8 girls (mean age 8.8 ± 1.4 years) showed no adverse events until maximal exertion. The mean parameters measured at peak exercise did not differ significantly between both examinations (mean peak VO2 = 42.7 ± 9.5 vs 47.8 ± 12.9 ml/min/kg, p = 0.097, mean O2pulse 7.84 ± 1.9 ml/min vs. 6.89 ± 1.8, p = 0.064, mean VE/VCO2slope 33.4 ± 5.9 vs. 34.0 ± 5.3, p = 0.689). The only significant difference was the respiratory exchange rate (RER, 1.01 ± 0.08 vs 0.95 ± 0.08, p = 0.004). The measured respiratory gases (end-tidal O2 and CO2) decreased and respectively increased significantly in almost every step when wearing an FFP2 mask. However, these levels were well below hypercapnia and above hypoxia.

CONCLUSION

 In this study, no significant differences in the cardiorespiratory function at peak exercise could be discerned when wearing an FFP2/N95 face mask. While the end-tidal values for CO2 increased significantly and the end-tidal values for O2 decreased significantly, these values did never reach levels of hypercapnia or hypoxia. Furthermore, the children terminated the exercise at a lower RER and heart rate (HR) suggesting a subconscious awareness of the higher strain. Since the detrimental effects of limiting sports during the pandemic are well documented, stopping PE lessons altogether because of the minor physiological effects of wearing these masks instead of simply stopping pushing children to perform at their best seems premature and should be reconsidered in the future.

WHAT IS KNOWN

• Wearing a face mask has an influence on psychological, social, and physiological functions in adults. • Because of the observed effects of wearing face masks in adults, physical activity in children was limited during the pandemic.

WHAT IS NEW

• Wearing an FFP2/N95 mask during physical activity did not lead to hypercapnia or hypoxia in children in this study. • Even though end-tidal CO2 values were significantly higher and end-tidal O2 values significantly lower when wearing an FFP2/N95 face mask, no pathological values were reached.