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Objectives: To compare the agreement, precision and repeatability of end tidal carbon dioxide (EtCO2 ) and transcutaneous carbon dioxide (TcCO2 ) with partial pressure of arterial CO(2) ( PaCO2) in postoperative neonates., Patients: Fifty mechanically ventilated neonates without lung disease, and with no contraindications for either TcCO2 or EtCO2 monitoring., Interventions: Paired TcCO2 and EtCO2 values were recorded with three consecutive measurements within the first 48 h of surgery., Main Outcome Measures: EtCO2, TcCO2 and PaCO2 triplets were compared using Bland-Altman plots., Results: One hundred thirty-two triplet measures of CO(2) were recorded with mean PaCO2 43.5 (7.3) mm Hg, EtCO2 38.8 (6.4) mm Hg and 43.8 (8.8) mm Hg (p<0.0001 for EtCO2 against PaCO2; paired t test). The PaCO2 - EtCO2 bias±2SD was 4.1±9.0 mm Hg and -0.8±13.0 mm Hg for PaCO2 - TcCO2. 56.1% of EtCO2, and 60.6% of TcCO2 values were within ±5 mm Hg of paired PaCO2., Conclusions: In postoperative neonates, EtCO2 and TcCO2 demonstrated a clinically acceptable agreement with PaCO2.

Objectives: Volume-targeted ventilation (VTV) is widely used and may reduce lung injury, but this assumes the clinically set tidal volume (VTset) is accurately delivered. This prospective observational study aimed to determine the relationship between VTset, expiratory VT (VTe) and endotracheal tube leak in a modern neonatal -volume-targeted ventilator (VTV) and the resultant partial arterial pressure of carbon dioxide (PaCO2) relationship with and without VTV.Design: Continuous inflations were recorded for 24 hours in 100 infants, mean (SD) 34 (4) weeks gestation and 2483 (985) g birth weight, receiving synchronised mechanical ventilation (SLE5000, SLE, UK) with or without VTV and either the manufacturer's V4 (n=50) or newer V5 (n=50) VTV algorithm. The VTset, VTe and leak were determined for each inflation (maximum 90 000/infant). If PaCO2 was sampled (maximum of 2 per infant), this was compared with the average VTe data from the preceding 15 min.Results: A total of 7 497 137 inflations were analysed. With VTV enabled (77 infants), the VTset-VTe bias (95% CI) was 0.03 (-0.12 to 0.19) mL/kg, with a median of 80% of VTe being ±1.0 mL/kg of VTset. Endotracheal tube leak up to 30% influenced VTset-VTe bias with the V4 (r2=-0.64, p<0.0001; linear regression) but not V5 algorithm (r2=0.04, p=0.21). There was an inverse linear relationship between VTe and PaCO2 without VTV (r2=0.26, p=0.004), but not with VTV (r2=0.04, p=0.10), and less PaCO2 within 40-60 mm Hg, 53% versus 72%, relative risk (95% CI) 1.7 (1.0 to 2.9).Conclusion: VTV was accurate and reliable even with moderate leak and PaCO2 more stable. VTV algorithm differences may exist in other devices. [ABSTRACT FROM AUTHOR]