Capnometry after an inspiratory breath hold, _PLATCO₂, as a surrogate for PaCO2 ${P}_{{\mathrm{aCO}}_{2}}$ in mild to moderate pediatric acute respiratory distress syndrome: A feasibility study

Abstract

ObjectiveAccurate and reliable noninvasive methods to estimate gas exchange are necessary to guide clinical decisions to avoid frequent blood samples in children with pediatric acute respiratory distress syndrome (PARDS). We aimed to investigate the correlation and agreement between end‐tidal measured immediately after a 3‐s inspiratory‐hold (PLATCO2) by capnometry and measured by arterial blood gases (ABG) in PARDS.DesignProspective cohort study.SettingSeven‐bed Pediatric Intensive Care Unit, Hospital El Carmen de Maipú, Chile.PatientsThirteen mechanically ventilated patients aged ≤15 years old undergoing neuromuscular blockade as part of management for PARDS.InterventionsNone.Measurements and Main ResultsAll patients were in volume‐controlled ventilation mode. The regular end‐tidal (without the inspiratory hold) was registered immediately after the ABG sample. An inspiratory‐hold of 3 s was performed for lung mechanics measurements, recording in the breath following the inspiratory‐hold. (PLATCO2). End‐tidal alveolar dead space fraction (AVDSf) was calculated as and its surrogate (S)AVDSf as . Measurements of were considered the gold standard. We performed concordance correlation coefficient (ρc), Spearman's correlation (rho), and Bland–Altmann's analysis (mean difference ± SD [limits of agreement, LoA]). Eleven patients were included, with a median (interquartile range) age of 5 (2–11) months. Tidal volume was 5.8 (5.7–6.3) mL/kg, PEEP 8 (6–8), driving pressure 10 (8–11), and plateau pressure 17 (17–19) cm H2O. Forty‐one paired measurements were analyzed. was higher than (52 mmHg [48–54] vs. 42 mmHg [38–45], p < 0.01), and there were no significant differences with PLATCO2 (50 mmHg [46–55], p > 0.99). The concordance correlation coefficient and Spearman's correlation between and PLATCO2 were robust (ρc = 0.80 [95% confidence interval [CI]: 0.67–0.90]; and rho = 0.80, p < 0.001.), and for were weak and strong (ρc = 0.27 [95% CI: 0.15–0.38]; and rho = 0.63, p < 0.01). The bias between PLATCO2 and was −0.4 ± 3.5 mmHg (LoA −7.2 to 6.4), and between and was −8.5 ± 4.1 mmHg (LoA −16.6 to −0.5). The correlation between AVDSf and (S)AVDSf was moderate (rho = 0.55, p < 0.01), and the mean difference was −0.5 ± 5.6% (LoA −11.5 to 10.5).ConclusionThis pilot study showed the feasibility of measuring end‐tidal CO2 after a 3‐s end‐inspiratory breath hole in pediatric patients undergoing controlled ventilation for ARDS. Encouraging preliminary results warrant further study of this technique.