Introduction: Arterial blood gas analysis (ABG) is the gold standard test for carbon dioxide measurement. End-tidal PCO 2 (PetCO 2) and transcutaneous PCO 2 (PtcCO 2) are noninvasive alternative methods. Objective: To examine the use of PetCO 2 and PtcCO 2 as PaCO 2 surrogates in awake children. Methods: A prospective observational study. Consecutive awake children in a stable condition referred to the Sleep Unit of Hospital de Pediatría Dr. J. P. Garrahan with suspected or confirmed sleep-related respiratory disorders requiring ABG were included. PetCO 2 and PtcCO 2 were recorded simultaneously during arterial puncture. PetCO 2 and PtCO 2 values were compared with PaCO 2. Correlation coefficient and Bland-Altman analysis were applied. The sample size was calculated considering a mean difference ≤3 mmHg as clinically acceptable. Results: Sixty-eight sample sets were obtained from 67 patients. The median age was 9.11 years (0.23-18.76). During 94.1% of the procedures patients breathed spontaneously, 30% needed multiple punctures and 92% resulted in pain. Median (IQR) PaCO 2 (mmHg) was 36.3 (31.45; 40.90), PetCO 2 33.0 (29; 39) and PtcCO 2 38.8 (32.95; 43.32). Correlation and agreement for PaCO 2 /PetCO 2 and PaCO 2 / PtcCO 2 was r = .6 and .9, and media of bias = 2.83 (−9.97; 15.64) and −1.88 (−9.01; 5.24), respectively. Hypercapnia (PaCO 2 > 45.0 mmHg) was present in 8/68 (11.8%) samples. Sensitivity, specificity, positive predictive value and negative predictive value to detect hypercapnia with PetCO 2 was 38%, 98%, 75%, and 92%, respectively, and with PtcCO 2 , 100%, 90%, 57%, and 100%, respectively. Conclusion: PtcCO 2 showed better agreement with PaCO 2 than PetCO 2 but because of the wide dispersion of values, neither method can replace the gold standard. Transcutaneous CO 2 might be a good screening tool to detect hypercapnia in awake children.
Arterial blood gas analysis (ABG) is the gold standard test for carbon dioxide measurement. End-tidal PCO2 (PetCO2) and transcutaneous PCO2 (PtcCO2) are non-invasive alternative methods. Objective: to examine the use of PetCO2 and PtcCO2 as PaCO2surrogates in awake children. Methods: Prospective observational study. Consecutive awake children in stable condition referred to the Sleep Unit of Hospital de Pediatría Prof. Dr. J. P. Garrahan with suspected or confirmed SRRD requiring ABG were included. PetCO2 and PtcCO2 were recorded simultaneously during arterial puncture. PetCO2 and PtCO2 values were compared with PaCO2. Correlation coefficient and Bland-Altman analysis were applied. Sample size was calculated considering a mean difference [?] 3 mmHg as clinically acceptable. Results: 68 sample sets were obtained from 67 patients. Median age was 9.11 years (0.23-18.76). During 94.1% of the procedures patients breathed spontaneously, 30% needed
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