The value of ETCO2 measurement for COPD patients in the emergency department

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.

The association of regional cerebral oximetry and neurologically intact survival in a porcine model of cardiac arrest

Background

The objective of this study was to determine if regional cerebral oximetry (rSO2) assessed during CPR would be predictive of survival with favorable neurological function in a prolonged model of porcine cardiac arrest. This study also examined the relative predictive value of rSO2 and end-tidal carbon dioxide (ETCO2), separately and together.

Methods

This study is a post-hoc analysis of data from a previously published study that compared conventional CPR (C-CPR) and automated head-up positioning CPR (AHUP-CPR). Following 10 min of untreated ventricular fibrillation, 14 pigs were treated with either C-CPR (C-CPR) or AHUP-CPR. rSO2, ETCO2, and other hemodynamic parameters were measured continuously. Pigs were defibrillated after 19 min of CPR. Neurological function was assessed 24 h later.

Results

There were 7 pigs in the neurologically intact group and 7 pigs in the poor outcomes group. Within 6 min of starting CPR, the mean difference in rSO2 by 95% confidence intervals between the groups became statistically significant (p < 0.05). The receiver operating curve for rSO2 to predict survival with favorable neurological function reached a maximal area under the curve value after 6 min of CPR (1.0). The correlation coefficient between rSO2 and ETCO2 during CPR increased towards 1.0 over time. The combined predictive value of both parameters was similar to either parameter alone.

Conclusion

Significantly higher rSO2 values were observed within less than 6 min after starting CPR in the pigs that survived versus those that died. rSO2 values were highly predictive of survival with favorable neurological function.

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.

Continuous positive airway pressure for treating hypoxemia due to pulmonary vein injury: A case report

BACKGROUND

Vascular injury during thoracoscopic surgery for esophageal cancer is a rare but life-threatening complication that can lead to severe hypotension and hypoxemia. Anesthesiologists need to provide rapid and effective treatment to save patients' lives.

CASE SUMMARY

A 54-year-old male patient was scheduled to undergo a thoracoscopic-assisted radical resection of esophageal cancer through the upper abdomen and right chest. While dissociating the esophagus from the carina through the right chest, unexpected profuse bleeding occurred from a suspected pulmonary vascular hemorrhage. While the surgeon attempted to achieve hemostasis, the patient developed severe hypoxemia. The anesthesiologist implemented continuous positive airway pressure (CPAP) using a bronchial blocker (BB), which effectively improved the patient’s oxygenation and the operation was completed successfully.

CONCLUSION

CPAP using a BB can resolve severe hypoxemia caused by accidental injury of the left inferior pulmonary vein during surgery.

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.

Relationship between end-tidal carbon dioxide and arterial carbon dioxide in critically ill patients on mechanical ventilation: A cross-sectional study

So far, only a few studies have examined and confirmed the correlation between end-expiratory carbon dioxide partial pressure (PETCO2) and arterial carbon dioxide tension (PaCO2) during invasive mechanical ventilation in critically ill patients. This study aimed to observe the correlation between PaCO2 and PETCO2 in patients on invasive mechanical ventilation.This was a cross-sectional study of adult patients on invasive mechanical ventilation enrolled between June 2018 and March 2019. Patients requiring invasive mechanical ventilation underwent one of the following mechanical ventilation modes: assisted/controlled ventilation, synchronized intermittent mandatory ventilation, and spontaneous breathing. Subsequently, the difference and correlation between PETCO2 and PaCO2 were analyzed.A total of 184 patients with 298 pairs of PETCO2-PaCO2 data were included in the analysis. Without distinguishing the ventilator mode, there was significant positive correlation between PETCO2 and PaCO2. In different ventilator modes, the correlation coefficient was 0.81 for synchronized intermittent mandatory ventilation, 0.47 for assisted/controlled ventilation, and 0.55 for spontaneous breathing, respectively. In patients with chronic obstructive pulmonary disease (r = 0.80), multiple trauma (r = 0.64), severe pneumonia (r = 0.60), gastrointestinal surgery (r = 0.57), and cerebrovascular diseases (r = 0.53), PETCO2 and PaCO2 were positively correlated. For oxygenation index <200 mm Hg, correlation coefficient r = 0.69, P < .001; oxygenation index ≥200, r = 0.73, P < .001. Under different oxygenation indexes, there was no statistically significant difference between the 2 correlation coefficients. Among 116 pairs of data with oxygenation index <200 mm Hg, the difference of PaCO2-PETCO2 ≥10 mm Hg was found in 25 pairs (21.55%); in 182 pairs of data with oxygenation index ≥200 mm Hg, the difference of PaCO2-PETCO2 ≥10 mm Hg was found in 26 pairsIn patients on invasive mechanical ventilation, there was a good correlation between PETCO2 and PaCO2 in different ventilator modes, different disease types, and different oxygenation indexes, especially in synchronized intermittent mandatory ventilation mode and chronic obstructive pulmonary disease patients.

Correlation of PaCO2 and ETCO2 in COPD Patients with Exacerbation on Mechanical Ventilation

Introduction: Chronic obstructive pulmonary disease (COPD) patients in hypercapnic respiratory failure require multiple arterial blood gas (ABG) analysis for monitoring. It is a painful, invasive, and expensive investigation. This study was aimed at finding an agreement between end-tidal carbon dioxide (ETCO₂, a noninvasive modality) and arterial carbon dioxide (PaCO₂) in COPD patients with acute exacerbation on mechanical ventilation. Materials and methods: A prospective observational study was conducted in COPD patients who required mechanical ventilation. ETCO₂ was recorded by mainstream capnography along with ABG analysis. An agreement between PaCO₂ and ETCO₂ was assessed. The effect of various factors on correlation was also studied. Results: A total of 100 patients with COPD in hypercapnic respiratory failure were included. Seventy-three percentage of patients were managed on invasive mechanical ventilation (IMV). The mean ETCO₂ and PaCO₂ were 48.66 ± 15.57 mm Hg and 75.52 ± 21.9 mm Hg, respectively. There was a significant correlation between PaCO₂ and ETCO₂ values (r = 0.82, 95% confidence interval of r = 0.78-0.86, p <0.0001). The Bland-Altman analysis shows the mean bias as -19.4 (95% limits of agreement = -40.0-1.1). Pearson's correlation coefficient was 0.84 in intubated patients and 0.58 in patients on noninvasive ventilation (NIV). Pearson's correlation coefficient between PaCO₂ and ETCO₂ in subjects with consolidation, cardiomegaly, hypotension, and raised pulmonary artery pressures was 0.78, 0.86, 0.85, and 0.86, respectively. Conclusion: Mainstream ETCO₂ measurement accurately predicts the PaCO₂ in COPD patients on IMV. However, for patients on NIV, ETCO₂ is insufficient in monitoring PaCO₂ levels due to weak correlation. Clinical significance: ETCO₂ can be used as a noninvasive modality in intensive care unit for monitoring the PaCO₂ in COPD patients on IMV. This can reduce the requirement of arterial blood sampling to a minimum number, in turn, reducing the cost of the treatment and discomfort to the patients. How to cite this article: Tyagi D, Govindagoudar MB, Jakka S, Chandra S, Chaudhry D. Correlation of PaCO₂ and ETCO₂ in COPD Patients with Exacerbation on Mechanical Ventilation. Indian J Crit Care Med 2021;25(3):305-309.

Comparing the novel microstream and the traditional mainstream method of end-tidal CO2 monitoring with respect to PaCO2 as gold standard in intubated critically ill children

The objective of this study was to evaluate a novel microstream method by comparison with PaCO₂ and the more standard mainstream capnometer in intubated pediatric patients. We hypothesized that the novel microstream method would superior compared to the traditional mainstream method in predicting PaCO₂. This was a prospective single-center comparative study. The study was carried out on 174 subjects with a total of 1338 values for each method. Data were collected prospectively from mainstream and microstream capnometer simultaneously and compared with PaCO₂ results. Although both mainstream PetCO₂ (mainPetCO₂) and microstream PetCO₂ (microPetCO₂) were moderately correlated (r = 0.63 and r = 0.68, respectively) with PaCO₂ values, mainPetCO₂ was in better agreement with PaCO₂ in all subjects (bias ± precision values of 3.8 ± 8.9 and 7.3 ± 8.2 mmHg, respectively). In those with severe pulmonary disease, the mainPetCO₂ and microPetCO₂ methods were highly correlated with PaCO₂ (r = 0.80 and r = 0.81, respectively); however, the biases of both methods increased (14.8 ± 9.1 mmHg and 16.2 ± 9.0 mmHg, respectively). In cases with increased physiologic dead space ventilation, the agreement levels of mainPetCO₂ and microPetCO₂ methods became distorted (bias ± precision values of 20.9 ± 11.2 and 25.0 ± 11.8 mm Hg, respectively) even though mainPetCO₂ and microPetCO₂ were highly correlated (r = 0.78 and r = 0.78, respectively). It was found that the novel microstream capnometer method for PetCO₂ measurements provided no superiority to the traditional mainstream method. Both capnometer methods may be useful in predicting the trend of PaCO₂ due to significant correlations with the gold standard measurement in cases with severe pulmonary disease or increased physiological dead space –despite reduced accuracy.

The correlation between end-tidal carbon dioxide and arterial blood gas parameters in patients evaluated for metabolic acid-base disorders

Background:

The analysis of arterial blood gas (ABG) is an invasive procedure that is used frequently in the emergency department (ED) to evaluate the acid-base status of critically-ill patients. However, capnometry is an alternative procedure that has been used in recent years to determine the metabolic status of patients’ blood. Considering the correlation between end-tidal carbon dioxide (ETCO₂) and arterial partial pressure of carbon dioxide (PaCO₂) identified in the previous studies and the strong correlation between PaCO₂ and bicarbonate (HCO_3⁻), we assumed that ETCO₂ might be a useful parameter in predicting the presence of metabolic acidosis. The aim of this study was to determine the correlation between ETCO₂ and the parameters of ABG in adult patients who were likely present metabolic acid-base disturbances in the Emergency Department of Imam Reza Hospital, the largest academic hospital in Mashhad in northeast Iran.

Methods:

This was a cross-sectional study conducted during six months on 62 adult patients who presented with suspected metabolic acid-base disorders to the ED. The exclusion criteria were patients with chronic obstructive pulmonary diseases, loss of consciousness, intubated patients, and those who were unable to tolerate capnography. The patients’ demographic information and vital signs were recorded. Also, ABG and ETCO₂ results were recorded. The Pearson product moment correlation analysis and linear regression were used to determine the correlation between ETCO₂ and ABG parameters.

Results:

Sixty-four patients were enrolled, consisting of 37 men and 27 women with a mean age of 55.4 ± 22.7 years. The most common complaints presented were nausea and vomiting (n = 24). The average value for ETCO₂ was 26.2 ± 6.1. There were significant linear correlations between ETCO₂ level, pH (r = 0.368), HCO_3⁻ (r = 0.869), PaCO₂ (r = 0.795), and Base Excess (B.E.) (r = 0.346). HCO₃ and PaCO₂ were the significant predictor values for ETCO₂ (linear regression analysis).

Conclusion:

ETCO₂ can be an appropriate indicator to estimate HCO_3⁻ and PaCO₂ in critical emergency situations, but it cannot be used as an indicator to estimate all ABG variables.