Abstract
Background:
Invasive measurement of PCO2 is frequently obtained and necessary in guiding care in patients presenting with an exacerbation of COPD but rare in the outpatient setting to evaluate hypercapnia in stable COPD patients. Transcutaneous CO2 monitoring (TcPCO2) in the clinic setting for COPD patients is often measured when evaluating those using NIV during sleep but may also serve as a viable alternative to assess hypercapnia in stable patients with COPD. We aim to evaluate the novel use of TcPCO2 measurement during COPD clinic visits.
Methods:
A retrospective chart analysis was performed on 30 COPD patients with TcPCO2 measurements seen in the UC Davis COPD Clinic between November 2021 and May 2022. TcPCO2 monitoring was performed with the Sentec Digital Monitoring System with the sensor application using a multi-site attachment ring. The sensor was placed on either the forehead or upper arm at 42 degrees Celsius per manufacturer guidelines. TcPCO2 levels were documented once stabilization of PCO2 was reached. Our primary objective was correlation between TcPCO2 measurement and COPD stage or classification. Secondary assessments were differences in BMI, sex, %RV, symptomology scores, and exacerbation rates. Descriptive statistical analysis was performed with Chi square, Student t-test, and 95% confidence intervals when appropriate.
Results:
Of the 30 COPD patients with TcPCO2 measurements, 59% (n = 19) had TcPCO2 of ≤45 mm Hg (M = 40 mm Hg ± 3.4) and 41% (n = 12) had TcPCO2 >45 mm Hg (M = 57.8 mm Hg ± 9.8). Of the patients with a TcPCO2 reading of ≤45 mm Hg, 19% (n = 4) were GOLD class A, 28% (n = 6) were GOLD class B, 52% (n = 11) were GOLD class D. In those with >45 mm Hg readings, 33% (n = 4) were GOLD class B and 67% (n = 8) were GOLD Class D. There was no correlation between TcPCO2 levels and GOLD classification of COPD, P = .27. Mean COPD stage for patients with a TcPCO2 reading of ≤45 mm Hg was 2.9 (± 1.0) vs. 2.8 (± 0.7), P = .57. We also observed no correlation between TcPCO2 levels ≤45 mm Hg and >45 mm Hg with BMI (P = .25), sex (P = .31), or exacerbation rates (P = .63). We also found no difference in %RV (P = .56) and symptomology scores (P = .86).
Conclusions:
No correlation was found in TcPCO2 measurements and COPD stage, GOLD classification, or any secondary finding. Due to the limited sample size, further research is warranted. Lack of correlation may attest to evaluation of PCO2 in any patient with COPD for consideration of necessary interventions (eg, sleep study referrals or NIV) to promote individualized therapy.
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