(118) Capnography- Derived Plateau CO₂ by Inspiratory Hold to Estimate PaCO₂ in a Swine Model of Pediatric ARDS

Background: Pediatric acute respiratory distress syndrome (PARDS) accounts for approximately 4% of PICU admissions. Patients with severe PARDS often require invasive mechanical ventilation, with current monitoring relying heavily on arterial blood gases (ABGs). End-tidal CO₂ (ETCO₂) offers a non-invasive alternative, but its accuracy is limited by dead space in ARDS. An end-inspiratory pause (EIP) could potentially reduce the dead space effect and enhance CO₂ elimination, enabling a more accurate real-time estimation of PaCO₂. This could potentially improve patient outcomes and decrease complications.

Objectives: This study aims to investigate whether EIPs can reduce dead space effects and improve PETCO₂ accuracy, limiting the need for arterial blood gases in a PARDS swine model.

Design/Methods: 11 juvenile pigs were sedated and mechanically ventilated. ARDS was induced by continuous oleic acid infusion. Infusion was started at 0.05 ml/kg and increased to 0.1 ml/kg after 15-30 minutes, then titrated by 0.05- 0.1 ml/kg 15-30 min up to a max of 0.6 ml/kg to achieve a PaO₂ of less than 200 mmHg. Hemodynamic and respiratory variables were continuously monitored using invasive and noninvasive monitoring, including volumetric and capnography. Before inducing PARDS, three EIPs (3, 5, and 10s) were performed, and ETCO₂ values were recorded. Each EIP was followed by 5-minute re-regulation periods. This was repeated once animals met PARDS criteria. Values for PaCO₂, ETCO₂, and other metrics were aligned at corresponding time points to assess for correlations.

Results: The study involved n = 11 pigs (55% male) having an average age (SD) of 68.6 (14.1) days and weighing 20.7 (1.70) Kg, on average. Time to reach ARDS ranged between 47–205 minutes with a median [IQR] of 114 [88, 158] minutes. 66 measurements were performed. Comparisons between PaCO₂, PETCO₂, and ETCO₂ will be included in the finished results. Alveolar dead space fraction (AVDSf) and dead space to tidal volume ratio (Vd/Vt) will also be reported on. Data analysis will be completed and updated by 8/1/2025.

Conclusions: This study is the first to investigate the relationship between different EIPs and the reduction of dead space in a pediatric swine ARDS model.