Background: CO2 is used in acute care settings to guide care for patients with exacerbations of COPD but less common in outpatient settings to evaluate hypercapnia in stable COPD. Transcutaneous CO2 (PtcCO2) monitoring may serve to assess hypercapnia during clinic visits. We previously published outcomes on 30 COPD patients seen in our clinic and found no correlation of PtcCO2levels in GOLD classification, COPD stages, or other secondary findings. This study continues the evaluation of novel use of PtcCO2measurement in patients referred to our COPD clinic. Methods: A retrospective chart analysis was performed on 132 COPD patients with PtcCO2measurements seen in the UC Davis Comprehensive COPD Clinic between November 2021 and February 2023. PtcCO2monitoring was performed utilizing the Sentec Digital Monitoring System with the sensor application that uses a multi-site attachment ring. The sensor was placed on either the forehead or upper arm at 42°C per manufacturer guidelines. PtcCO2levels were documented once stabilization of PCO2 was reached. Our primary objective was correlation between PtcCO2measurement and COPD stage and GOLD classification. Secondary assessments of BMI, exacerbation rates, %RV, symptomology scores, and oxygenation were evaluated. Descriptive statistical analysis was performed with Chi square and student t-test when appropriate. Results: Of 132 COPD patients with spirometry 59% (n = 78) had PtcCO2of ≤45 mm Hg and 41% (n = 54) had PtcCO2>45 mm Hg. Of the patients with a PtcCO2reading of ≤45 mm Hg, 44% (n = 11) had stage 1 COPD, 45% (n = 28) had stage 2, 24% (n = 15) had stage 3, and 13% (n = 8) had stage 4. In those with >45 mm Hg readings, 9% (n = 2) had stage 1 COPD, 36% (n = 16) were stage 2, 43% (n = 19) were stage 3, and 16% (n = 7) were stage 4. There were demonstrated differences between the two PtcCO2groups and COPD stage (P = .042) but no correlation between PtcCO2levels and GOLD classification of COPD (P = .45). Secondary outcomes for BMI (P = .19), exacerbation rates (P = .47), %RV (P = .24) and symptom scores (P = .93) did not show differences. Oxygen was utilized in 38% (n = 30) of patients with ≤45 mm Hg PtcCO2and 57% (n = 31) of patients with >45 mm Hg readings (P = 45 mm Hg PtcCO2. No correlation was found in GOLD classification, BMI, exacerbation rates, %RV, symptomology scores in the two PtcCO2cohorts.
Heath et al. (Sun,) studied this question.