Agreement Between Transcutaneous Monitoring and Arterial Blood Gases During COPD Exacerbation

Comparative analysis of hemoglobin, potassium, sodium, and glucose in arterial blood gas and venous blood of patients with COPD

The study aims to assess the accuracy of the arterial blood gas (ABG) analysis in measuring hemoglobin, potassium, sodium, and glucose concentrations in comparison to standard venous blood analysis among patients diagnosed with chronic obstructive pulmonary disease (COPD). From January to March 2023, results of ABG analysis and simultaneous venous blood sampling among patients with COPD were retrospectively compared, without any intervention being applied between the two methods. The differences in hemoglobin, potassium, sodium, and glucose concentrations were assessed using a statistical software program (R software). There were significant differences in the mean concentrations of hemoglobin (p < 0.001), potassium (p < 0.001), and sodium (p = 0.001) between the results from ABG and standard venous blood analysis. However, the magnitude of the difference was within the total error allowance (TEa) of the United States of Clinical Laboratory Improvement Amendments (US-CLIA). As for the innovatively studied glucose concentrations, a statistically significant difference between the results obtained from ABG (7.8 ± 3.00) mmol·L-1 and venous blood (6.72 ± 2.44) mmol·L-1 was noted (p < 0.001), with the difference exceeding the TEa of US-CLIA. A linear relationship between venous blood glucose and ABG was obtained: venous blood glucose (mmol·L-1) =  - 0.487 + 0.923 × ABG glucose (mmol·L-1), with R2 of 0.882. The hemoglobin, potassium, and sodium concentrations in ABG were reliable for guiding treatment in managing COPD emergencies. However, the ABG analysis of glucose was significantly higher as compared to venous blood glucose, and there was a positive correlation between the two methods. Thus, a linear regression equation in this study combined with ABG analysis could be helpful in quickly estimating venous blood glucose during COPD emergency treatment before the standard venous blood glucose was available from the medical laboratory.

Associations between clinical interventions and transcutaneous blood gas values in postoperative patients

PURPOSE

Postoperative monitoring of circulation and respiration is pivotal to guide intervention strategies and ensure patient outcomes. Transcutaneous blood gas monitoring (TCM) may allow for noninvasive assessment of changes in cardiopulmonary function after surgery, including a more direct assessment of local micro-perfusion and metabolism. To form the basis for studies assessing the clinical impact of TCM complication detection and goal-directed-therapy, we examined the association between clinical interventions in the postoperative period and changes in transcutaneous blood gasses.

METHODS

Two-hundred adult patients who have had major surgery were enrolled prospectively and monitored with transcutaneous blood gas measurements (oxygen (TcPO2) and carbon dioxide (TcPCO2)) for 2 h in the post anaesthesia care unit, with recording of all clinical interventions. The primary outcome was changes in TcPO2, secondarily TcPCO2, from 5 min before a clinical intervention versus 5 min after, analysed with paired t-test.

RESULTS

Data from 190 patients with 686 interventions were analysed. During clinical interventions, a mean change in TcPO2 of 0.99 mmHg (95% CI-1.79-0.2, p = 0.015) and TcPCO2 of-0.67 mmHg (95% CI 0.36-0.98, p < 0.001) was detected.

CONCLUSION

Clinical interventions resulted in significant changes in transcutaneous oxygen and carbon dioxide. These findings suggest future studies to assess the clinical value of changes in transcutaneous PO2 and PCO2 in a postoperative setting.

TRIAL REGISTRY

Clinical trial number: NCT04735380.

CLINICAL TRIAL REGISTRY

https://clinicaltrials.gov/ct2/show/NCT04735380.

Prospective, observational study investigating the level of agreement between transcutaneous and invasive carbon dioxide measurements in critically ill emergency department patients

BACKGROUND

Transcutaneous carbon dioxide (Ptcco2) measurement is a non-invasive surrogate marker for arterial carbon dioxide (Paco2), which requires invasive arterial blood sampling. Use of Ptcco2 has been examined in different clinical settings, however, most existing evidence in the adult emergency department (ED) setting shows insufficient agreement between the measurements. This study assessed the level of agreement between Ptcco2 and Paco2 in undifferentiated adult ED patients across multiple timepoints.

METHODS

This prospective observational study (study period 2020-2021) assessed paired Ptcco2 and Paco2 measurements at four consecutive timepoints (0, 30, 60 and 90 min) in adult (aged 18 years or over) Australian ED patients requiring hospital admission and arterial catheter insertion. Agreement between the pairs was assessed using Bland-Altman analysis. It was prospectively determined by expert consensus that limits of ±4 mm Hg would be a clinically acceptable level of agreement between Ptcco2 and Paco2.

RESULTS

During the study period 168 paired Ptcco2 and Paco2 readings were taken from 42 adult ED patients. Bland-Altman analysis showed a mean Ptcco2 reading 3.85 mm Hg higher than Paco2, although at each timepoint the 95% CIs breached the limit of 4 mm Hg difference. In addition, only 66% (111/168) of results fell within the clinically acceptable range.

CONCLUSION

The level of agreement between Ptcco2 and Paco2 measurements may not be sufficiently precise for the adoption of Ptcco2 monitoring in patients presenting to the ED.

Utility of Initial Arterial Blood Gas in Neuromuscular versus Non-Neuromuscular Acute Respiratory Failure in Intensive Care Unit Patients

Background: The arterial blood gas (ABG) parameters of patients admitted to intensive care units (ICUs) with acute neuromuscular respiratory failure (NMRF) and non-NMRF have not been defined or compared in the literature. Methods: We retrospectively collected the initial ABG parameters (pH, PaCO2, PaO2, and HCO3) of patients admitted to ICUs with acute respiratory failure. We compared ABG parameter ranges and the prevalence of abnormalities in NMRF versus non-NMRF and its categories, including primary pulmonary disease (PPD) (chronic obstructive pulmonary disease, asthma, and bronchiectasis), pneumonia, and pulmonary edema. Results: We included 287 patients (NMRF, n = 69; non-NMRF, n = 218). The difference between NMRF and non-NMRF included the median (interquartile range (IQR)) of pH (7.39 (7.32−7.43), 7.33 (7.22−7.39), p < 0.001), PaO2 (86.9 (71.4−123), 79.6 (64.6−99.1) mmHg, p = 0.02), and HCO3 (24.85 (22.9−27.8), 23.4 (19.4−26.8) mmol/L, p = 0.006). We found differences in the median of PaCO2 in NMRF (41.5 mmHg) versus PPD (63.3 mmHg), PaO2 in NMRF (86.9 mmHg) versus pneumonia (74.3 mmHg), and HCO3 in NMRF (24.8 mmol/L) versus pulmonary edema (20.9 mmol/L) (all p < 0.01). NMRF compared to non-NMRF patients had a lower frequency of hypercarbia (24.6% versus 39.9%) and hypoxia (33.8% versus 50.5%) (all p < 0.05). NMRF compared to PPD patients had lower frequency of combined hypoxia and hypercarbia (13.2% versus 37.8%) but more frequently isolated high bicarbonate (33.8% versus 8.9%) (all p < 0.001). Conclusions: The ranges of ABG changes in NMRF patients differed from those of non-NMRF patients, with a greater reduction in PaO2 in non-NMRF than in NMRF patients. Combined hypoxemia and hypercarbia were most frequent in PPD patients, whereas isolated high bicarbonate was most frequent in NMRF patients.