Capnometry after an inspiratory breath hold, _PLATCO₂, as a surrogate for in mild to moderate pediatric acute respiratory distress syndrome: A feasibility study

Objective: Accurate 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 (Figure presented.) measured immediately after a 3-s inspiratory-hold (_PLATCO₂) by capnometry and (Figure presented.) measured by arterial blood gases (ABG) in PARDS. Design: Prospective cohort study. Setting: Seven-bed Pediatric Intensive Care Unit, Hospital El Carmen de Maipú, Chile. Patients: Thirteen mechanically ventilated patients aged ≤15 years old undergoing neuromuscular blockade as part of management for PARDS. Interventions: None. Measurements and Main Results: All patients were in volume-controlled ventilation mode. The regular end-tidal (Figure presented.) (without the inspiratory hold) was registered immediately after the ABG sample. An inspiratory-hold of 3 s was performed for lung mechanics measurements, recording (Figure presented.) in the breath following the inspiratory-hold. (_PLATCO₂). End-tidal alveolar dead space fraction (AVDSf) was calculated as (Figure presented.) and its surrogate (S)AVDSf as (Figure presented.). Measurements of (Figure presented.) 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. (Figure presented.) was higher than (Figure presented.) (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 (Figure presented.) and _PLATCO₂ were robust (ρc = 0.80 [95% confidence interval [CI]: 0.67–0.90]; and rho = 0.80, p < 0.001.), and for (Figure presented.) 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 (Figure presented.) was −0.4 ± 3.5 mmHg (LoA −7.2 to 6.4), and between (Figure presented.) and (Figure presented.) 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). Conclusion: This 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.