The accuracy of mainstream end-tidal carbon dioxide levels to predict the severity of chronic obstructive pulmonary disease exacerbations presented to the ED

Investigation of the Relationship Between the Measured Alpha Angle in Capnography and Readmission Within Thirty Days in Chronic Obstructive Pulmonary Disease Patients Who Presented to the Emergency Department

BACKGROUND

Individuals with chronic obstructive pulmonary disease (COPD) constitute a significant portion of patients who present to the emergency department with dyspnea. However, there is no ideal method for predicting mortality or making hospitalization decisions in the emergency department (ED). In this regard, objective findings are needed for these patients. Since there are no objective findings regarding the hospitalization decision, there may be an increase in the re-admission rate of patients who needed hospitalization but were decided to be discharged. Side-stream end-tidal carbon dioxide (EtCO2) measurements offer a non-invasive, easy-to-interpret, quickly accessible, and reproducible method that can be applied at the bedside.

OBJECTIVES

The aim of this study was to evaluate the relationship between the alpha angle values obtained by capnography and readmission rates within 30 days for patients experiencing COPD exacerbations who presented to the ED with dyspnea and were discharged after treatment.

METHODS

In this study, we studied with 130 participants presented to the emergency department of a tertiary care university hospital with dyspnea, who are >18 y. Forty patients were excluded after evaluation for eligibility for the study. Thus, the data of 90 patients included were analyzed. We obtained alpha angle and EtCO2 values for all patients at the time of admission and also after treatment. The primary outcome measure of the study was the relationship between the patients' readmission situations within 30 days of the alpha angle measurements. The secondary outcome measure was the association between patients' EtCO2 values ​​and readmission within 30 days.

RESULTS

It was observed that both the pretreatment alpha angle values and the posttreatment alpha angle variables were statistically significant in predicting the readmission of the patients within 30 days (p = 0.001, p = 0.003) CONCLUSION: The results of this study show that alpha angle values measured for patients with COPD who present to the ED with the complaint of dyspnea may be used to predict readmission.

Can end-tidal CO2 measurement replace arterial partial CO2 in emergency department respiratory distress management?

OBJECTIVE

To assess the feasibility of using end-tidal carbon dioxide (EtCO2) as a non-invasive substitute for partial pressure of arterial carbon dioxide (PaCO2) in emergency department (ED) triage and follow-up, and to explore the potential of partial pressure of venous carbon dioxide (PvCO2) as an alternative to PaCO2.

DESIGN

Prospective cross-sectional study.

SETTING

Tertiary university hospital.

PATIENTS OR PARTICIPANTS

97 patients presenting with acute respiratory distress to the ED.

INTERVENTIONS

EtCO2, arterial blood gases, and venous blood gases measured at admission (0 min), 60 min, and 120 min.

MAIN VARIABLES OF INTEREST

CO2 levels.

RESULTS

Among 97 patients (mean age: 70.93 ± 9.6 years; 60.8% male), EtCO2 > 45 mmHg at admission showed strong positive correlations with PaCO2 and PvCO2 (r = 0.844, r = 0.803; p < 0.001, respectively). Significant positive correlation was observed between 60-min EtCO2 and PaCO2 (r = 0.729; p < 0.001). Strong correlation between PaCO2 and PvCO2 at 120 min when EtCO2 > 45 mmHg (r = 0.870; p < 0.001). EtCO2 was higher in hospitalized patients compared to discharged ones.

CONCLUSIONS

EtCO2 appears promising as a substitute for PaCO2 in ED patients with acute respiratory distress within the initial two hours of treatment. Venous blood gas sampling offers a less invasive alternative to arterial sampling, facilitating simultaneous blood tests.

Utility of non-invasive monitoring of exhaled carbon dioxide and perfusion index in adult patients in the emergency department

BACKGROUND

Several noninvasive solutions are available for the assessment of patients at risk of deterioration. Capnography, in the form of end-tidal exhaled CO2 (ETCO2) and perfusion index (PI), could provide relevant information about patient prognosis. The aim of the present project was to determine the association of ETCO2 and PI with mortality of patients admitted to the emergency department (ED).

METHODS

Multicenter, prospective, cohort study of adult patients with acute disease who needed continuous monitoring in the ED. The study included two tertiary hospitals in Spain between October 2022 and June 2023. The primary outcome of the study was in-hospital mortality (all-cause). Demographics, vital signs, ETCO2 and PI were collected.

RESULTS

A total of 687 patients were included in the study. The in-hospital mortality rate was 6.8%. The median age was 79 years (IQR: 69-86), and 63.3% were males. The median ETCO2 value was 30 mmHg (26-35) in survivors and 23 mmHg (16-30) in nonsurvivors (p = 0.001). For the PI, the medians were 4.7% (2.8-8.1) for survivors and 2.5% (0.98-4-4) for nonsurvivors (p < 0.001). The model that presented the best AUC was age (odds ratio (OR): 1.02 (1.00-1.05)), the respiratory rate (OR: 1.06 (1.02-1.11)), and the PI (OR: 0.83 (0.75-0.91)), with a result of 0.840 (95% CI: 0.795-0.886); the model with the respiratory rate (OR: 1.05 (1.01-1.10)), the PI (OR: 0.84 (0.76-0.93)), and the ETCO2 (no statistically significant OR), with an AUC of 0.838 (95% CI: 0.787-0.889).

CONCLUSIONS

The present study showed that the PI and respiratory rate are independently associated with in-hospital mortality. Both the PI and ETCO2 are predictive parameters with improved prognostic performance compared with that of standard vital signs.

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.

Comparison of the Arterial PaCO 2 Values and ETCO 2 Values Measured with Sidestream Capnography in Patients with a Prediagnosis of COPD Exacerbation

Background  Aim of this study is to investigate whether end-tidal carbon dioxide (ETCO 2 ) values can be used instead of partial pressure of carbon dioxide (PaCO 2 ) values in guiding treatment, and determining treatment benefits in patients that received a pre-diagnosis of chronic obstructive pulmonary disease (COPD) exacerbation at the emergency department. Methods  This observational prospective study was conducted with patients who presented to the emergency department with the complaint of shortness of breath and were diagnosed with COPD exacerbation. ETCO 2 was measured with the sidestream method during blood gas analysis in patients with indications for this analysis. Measurements were repeated at hour 1 after treatment. Results  The study included a total of 121 cases. There was a positive correlation between the PaCO 2 and ETCO 2 values measured before and after treatment ( r  = 0.736, p  < 0.01 and r  = 0.883, p  < 0.01, respectively). High ETCO 2 values were accompanied by high PaCO 2 values. When the measurements before and after treatment were evaluated using the Bland-Altman method, most of the result were within the limits of agreement (-4.9 and +31.4/- 2.6 and +9.4), with mean differences being calculated as 13.2 and 8.4, respectively. Conclusions  Although ETCO 2 and PaCO 2 were statistically consistent according to the results of our study, due to the high averages of differences between these two parameters, the ETCO 2 value has limited clinical use in COPD cases compared to PaCO 2 . However, high ETCO 2 values may indicate that noninvasive mechanical ventilation should be included in the treatment of COPD cases without waiting for the results of blood gas analysis, and they can also be when needed for inpatient treatment.

Doppler ultrasound peak systolic velocity versus end tidal carbon dioxide during pulse checks in cardiac arrest

BACKGROUND

An accurate, non-invasive measure of return of spontaneous circulation (ROSC) is needed to improve management of cardiac arrest patients.

OBJECTIVES

During a pulse check in Emergency Department (ED) cardiac arrest patients, we compared the correlation between 1) end tidal carbon dioxide (ETCO₂) and systolic blood pressure (SBP), and 2) Doppler ultrasound peak systolic velocity (PSV) and SBP. Additionally, we assessed the accuracy of PSV ≥ 20 cm/sec in comparison to previously suggested ETCO₂ ≥ 20 or ≥ 25 mmHg thresholds to predict ROSC with SBP ≥ 60 mmHg.

METHODS

This was a secondary analysis of a previously published prospective observational study of ED cardiac arrest patients with an advanced airway and femoral arterial line in place. During each pulse check, highest SBP, highest PSV, and ETCO₂ at the end of the pulse check were recorded. Spearman correlation coefficients were calculated and compared using a Fisher Z-transformation. Accuracy of previously determined PSV and ETCO₂ thresholds for detecting ROSC with SBP ≥ 60 mmHg were compared using McNemar's tests.

RESULTS

Based on data from 35 patients with 111 pulse checks, we found a higher correlation between PSV and SBP than ETCO₂ and SBP (0.71 vs 0.31; p < 0.001). Diagnostic accuracy of PSV ≥ 20 cm/sec for detecting ROSC with SBP ≥ 60 mmHg was 89% (95% CI: 82%-94%) versus 59% (95% CI: 49%-68%) and 58% (95% CI: 48%-67%) for ETCO₂ ≥ 20 and ≥ 25 mmHg, respectively.

CONCLUSIONS

During a pulse check, Doppler ultrasound PSV outperformed ETCO₂ for correlation with SBP and accuracy in detecting ROSC with SBP ≥ 60 mmHg.

On Analyzing Capnogram as a Novel Method for Screening COVID-19: A Review on Assessment Methods for COVID-19

In November 2019, the novel coronavirus disease COVID-19 was reported in Wuhan city, China, and was reported in other countries around the globe. COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Strategies such as contact tracing and a vaccination program have been imposed to keep COVID-19 under control. Furthermore, a fast, noninvasive and reliable testing device is needed urgently to detect COVID-19, so that contact can be isolated and ringfenced before the virus spreads. Although the reverse transcription polymerase chain reaction (RT-PCR) test is considered the gold standard method for the diagnosis of SARS-CoV-2 infection, this test presents some limitations which cause delays in detecting the disease. The antigen rapid test (ART) test, on the other hand, is faster and cheaper than PCR, but is less sensitive, and may limit SARS-CoV-2 detection. While other tests are being developed, accurate, noninvasive and easy-to-use testing tools are in high demand for the rapid and extensive diagnosis of the disease. Therefore, this paper reviews current diagnostic methods for COVID-19. Following this, we propose the use of expired carbon dioxide (CO2) as an early screening tool for SARS-CoV-2 infection. This system has already been developed and has been tested on asthmatic patients. It has been proven that expired CO2, also known as capnogram, can help differentiate between respiratory conditions and, therefore, could be used to detect SARS-CoV-2 infection, as it causes respiratory tract-related diseases.

Acute Exacerbations of Chronic Obstructive Pulmonary Disease: A Primer for Emergency Physicians

BACKGROUND

Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) impose a significant burden on patients and the emergency health care system. Patients with COPD who present to the emergency department (ED) often have comorbidities that can complicate their management.

OBJECTIVE

To discuss strategies for the management of acute exacerbations in the ED, from initial assessment through disposition, to enable effective patient care and minimize the risk of treatment failure and prevent hospital readmissions.

DISCUSSION

Establishing a correct diagnosis early on is critical; therefore, initial evaluations should be aimed at differentiating COPD exacerbations from other life-threatening conditions. Disposition decisions are based on the intensity of symptoms, presence of comorbidities, severity of the disease, and response to therapy. Patients who are appropriate for discharge from the ED should be prescribed evidence-based treatments and smoking cessation to prevent disease progression. A patient-centric discharge care plan should include medication reconciliation; bedside "teach-back," wherein patients demonstrate proper inhaler usage; and prompt follow-up.

CONCLUSIONS

An effective assessment, accurate diagnosis, and appropriate discharge plan for patients with AECOPD could improve treatment outcomes, reduce hospitalization, and decrease unplanned repeat visits to the ED.

Usefulness of Measurement of End-tidal CO2 Using a Portable Capnometer in Patients with Chronic Respiratory Failure Receiving Long-term Oxygen Therapy

Objective Patients with chronic respiratory failure requiring long-term oxygen therapy (LTOT) are at a risk of CO₂ retention because of excessive oxygen administration. The CapnoEye™ is a novel portable capnometer that can measure end-tidal CO₂ (EtCO₂) noninvasively. This retrospective study evaluated the usefulness of this device. Methods EtCO₂ was measured using the CapnoEye™. The EtCO₂ and partial pressure of venous carbon dioxide (PvCO₂) were analyzed, and other clinical data were assessed. Patients Sixty-one consecutive patients with chronic respiratory failure receiving LTOT in the outpatient department at the Japanese Red Cross Medical Center between July 2017 and March 2018 were retrospectively reviewed. Results There was a significant correlation between EtCO₂ and PvCO₂ (r=0.63) in the total study population as well as in the COPD group (r=0.65) and ILD group (r=0.67). The PvCO₂ and EtCO₂ gradient was correlated with only the body mass index in a multivariate analysis (p=0.0235). The EtCO₂ levels on the day of admission were significantly higher than those in the same patients when they were in a stable condition (p=0.0049). There was a significant correlation between ΔEtCO₂ and ΔPvCO₂ (r=0.4). A receiver-operating characteristic curve analysis revealed the optimal cut-off EtCO₂ value for identifying hypercapnia to be 34 mmHg (p=0.0005). Conclusion The evaluation of EtCO₂ by the CapnoEye™ was useful for predicting PvCO₂. The body mass index was identified as a possible predictor of the PvCO₂ and EtCO₂ gradient. An increase in EtCO₂ may indicate deterioration of the respiratory status in patients with chronic respiratory failure receiving LTOT.

End tidal carbon dioxide monitoring in acute asthma: a prospective pilot study in emergency department patients

The peak expiratory flow rate (PEFR) is the gold standard for monitoring asthmatic patients. However, its measurement requires understanding and active participation. End tidal carbon dioxide (EtCO2) may be considered an accurate surrogate for PaCO2, a severity marker in acute asthma. We studied the use of EtCO2 as a monitoring tool in acute asthma.

PATIENTS AND METHODS

This was a prospective study that included consecutive patients admitted to our emergency department for acute asthma exacerbation. Data were collected at first medical contact (T0) and after 1 h of treatment (T60). The primary endpoint was the change in EtCO2; the secondary endpoints included changes in the EtCO2 Q angle value, plateau T time, and change in EtCO2 values for the patients with a PEFR ratio less than 50% after treatment.

RESULTS

Fifty-five patients were included and 36 waveforms were analysed. The mean age was 37 years and 26 (47%) were women. The median initial PEFR was 200 [interquartile range (IQR): 150-240]; the median EtCO2 at T0 and T60 was 35 (IQR: 30-38) and 34 (IQR: 29-37). There was no significant change in EtCO2 after treatment. There was no significant change in the Q angle and the T time after treatment. At T60, 20 (36%) patients had a PEFR ratio less than 50%. Change in EtCO2 from T60 to T0 was associated with a PEFR ratio less than 50%.

CONCLUSION

After 1 h of treatment, there was no significant change in EtCO2. A decrease in EtCO2 seems to be associated with a higher risk of PEFR ratio less than 50% after treatment.

Waveform capnography in a South African prehospital service: Knowledge assessment of paramedics

Background

Waveform capnography has proven to be of great value in the provision of safe patient care especially in the intubated patient. Although seldom available, or used in African contexts, capnography has become standard practice in well-resourced out-of-hospital services for confirmation of intubation, and optimization of resuscitation and ventilation. To date there has been little research into the knowledge of out-of-hospital staff, both local and internationally, utilising capnography. This study describes the knowledge of paramedics who use waveform capnography in the out-of-hospital environment.

Methods

A cohort of advanced life support qualified paramedics in a private ambulance service in South Africa undertook a web-based survey around their background, training and use of capnography. Participants’ knowledge was assessed by exploring their interpretation of waveform capnography and establishing attitudes pertaining to training and constraints of availability of capnography.

Results

Seventy eight paramedics responded, and most (91%) indicated they were likely to use capnography when the tool was available. The majority of training in capnography had been during their primary qualification (85%). Most participants indicated that they would like further training (91%). Use of capnography for confirmation of endotracheal tube placement and quality of compressions during cardiopulmonary resuscitation was well understood (correct in 94% and 84% respectively), while more complicated knowledge such as waveform changes during ventilation (66%) and the effect of hypovolaemia (48%) on capnography were lacking.

Conclusion

Paramedics report using waveform capnography extensively when it is available in the South African out-of-hospital environment. Although the knowledge around capnography and its usage was found to be good in most areas, more complicated scenarios exposed flaws in the knowledge of many paramedics and suggest the need for improved and ongoing training, as well as incorporation into curricula as the field develops across the continent.

Bland-Altman analysis: A paradigm to understand correlation and agreement

The rapid increase in the number of new laboratory methods has led to the necessity of reliable verification methods. Validation of a new measurement method for application to medical practice requires comparison with gold standard techniques. The Bland-Altman analysis is a frequently applied technique in studies that investigate the agreement between two methods of the same medical measurement. In this review, potential areas of usage of Bland-Altman analysis is elaborated from a clinical viewpoint, and possible pitfalls in study designs are discussed in statistical perspective.

Efficacy and Safety of Using High-Flow Nasal Oxygenation in Patients Undergoing Rapid Sequence Intubation

Objective

To assess the efficacy and safety of high-flow nasal oxygen (HFNO) therapy in patients undergoing rapid sequence intubation (RSI) for emergency abdominal surgery.

Methods

HFNO of 60 L.min^-1 at an inspiratory oxygen fraction of 1 was delivered 4 min before laryngoscopy and maintained until the patient was intubated, and correct intubation was verified by the appearance of the end-tidal CO₂ (EtCO₂) waveform. Transcutaneous oxygenation (SpO₂), heart rate and non-invasive mean arterial pressure were monitored at baseline (T0), after 4 min on HFNO (T1) and at the time of laryngoscopy (T2) and endotracheal intubation (ETI) (T3). An SpO₂ of <3% from baseline was recorded at any sampled time. The value of EtCO₂ at T3 was registered after two mechanical breaths. The apnoea time was defined as the time from the end of propofol injection to ETI. RSI was performed with propofol, fentanyl and rocuronium.

Results

Forty-five patients were enrolled. SpO₂ levels showed a statistically significant increase at T1, T2 and T3 compared with those at T0 (p<0.05); median SpO₂% (interquartile range) was 97% (range, 96%-99%) at T0, 99% (range, 99%-100%) at T1, 99% (range, 99%-100%) at T2 and 99% (range, 99%-100%) at T3. Minimal SpO₂ was 96%; no patient showed an SpO₂ of <3% from baseline; mean EtCO₂ at the time of ETI was 36±4 mmHg. Maximum apnoea time was 12 min.

Conclusion

HFNO is an effective and safe technique for pre-oxygenation in patients undergoing rapid sequence induction of general anaesthesia for emergency surgery.

Capnography in the Emergency Department: A Review of Uses, Waveforms, and Limitations

BACKGROUND

Capnography has many uses in the emergency department (ED) and critical care setting, most commonly cardiac arrest and procedural sedation.

OBJECTIVE OF THE REVIEW

This review evaluates several indications concerning capnography beyond cardiac arrest and procedural sedation in the ED, as well as limitations and specific waveforms.

DISCUSSION

Capnography includes the noninvasive measurement of CO₂, providing information on ventilation, perfusion, and metabolism in intubated and spontaneously breathing patients. Since the 1990s, capnography has been utilized extensively for cardiac arrest and procedural sedation. Qualitative capnography includes a colorimetric device, changing color on the amount of CO₂ present. Quantitative capnography provides a numeric value (end-tidal CO₂), and capnography most commonly includes a waveform as a function of time. Conditions in which capnography is informative include cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Patients with seizure, trauma, and respiratory conditions, such as pulmonary embolism and obstructive airway disease, can benefit from capnography, but further study is needed. Limitations include use of capnography in conditions with mixed pathophysiology, patients with low tidal volumes, and equipment malfunction. Capnography should be used in conjunction with clinical assessment.

CONCLUSIONS

Capnography demonstrates benefit in cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Further study is required in patients with seizure, trauma, and respiratory conditions. It should only be used in conjunction with other patient factors and clinical assessment.

Management of Acute Exacerbation of Asthma and Chronic Obstructive Pulmonary Disease in the Emergency Department

Acute asthma and chronic obstructive pulmonary disease (COPD) exacerbations are the most common respiratory diseases requiring emergent medical evaluation and treatment. Asthma and COPD are chronic, debilitating disease processes that have been differentiated traditionally by the presence or absence of reversible airflow obstruction. Asthma and COPD exacerbations impose an enormous economic burden on the US health care budget. In daily clinical practice, it is difficult to differentiate these 2 obstructive processes based on their symptoms, and on their nearly identical acute treatment strategies; major differences are important when discussing anatomic sites involved, long-term prognosis, and the nature of inflammatory markers.