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.
- mechanical ventilation
- tidal volume
- volume targeted ventilation
- lung injury
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Contributors DGT developed the concept and designed the experiment. OF, EJP, DB and JDP enrolled and studied all infants. DB designed and built the data collection system used in the study. OF, DB, MM and EJP were involved in data analysis. OF, PP-F, DB, MM and DGT interpreted the data. OF and DGT wrote the first draft of the manuscript and all authors contributed to redrafting the manuscript.
Funding This study is supported by the Victorian Government Operational Infrastructure Support Program (Melbourne, Australia). DGT is supported by a National Health and Medical Research Council Clinical Career Development Fellowship (grant ID 1053889).
Competing interests DGT has presented at conferences and workshops in which SLE, UK, has paid unrestricted travel costs or sponsorship for the meeting. DGT has also presented at conferences and workshops supported (including speaker travel costs) by other ventilator manufacturers, including Carefusion, Dräger, Fisher Paykel and Acutronic. No author received an honorarium, grant or other forms of payment to produce the manuscript. The study was not commissioned and no commercial agencies were involved in any aspect of this study. The authors have no other competing interests to declare.
Ethics approval The Royal Children’s Hospital Human Research and Ethics Committee. The study was approved as a low or negligible risk study meeting audit criteria and prospective parental consent was not deemed necessary.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement De-identified raw complete data (7 million inflations) for all 100 study subjects are available upon request from the corresponding author.