Objective High-frequency oscillatory ventilation (HFOV) is widely used in neonatology. The Dräger Babylog VN500 ventilator offers volume-guaranteed HFOV (HFOV-VG) mode when the high-frequency tidal volume (VThf) to be delivered can be set. We investigated how HFOV-VG maintains VThf in the short and longer term and how it affects other ventilator parameters and blood gases.
Methods We downloaded ~3.2 million seconds (36.7 days) of ventilator data from 17 infants ventilated using HFOV-VG during clinical care with 1 Hz sampling rate. To process and analyse the data, we used the Python computer language.
Results Overall, the median VThf was 1.93 mL/kg (IQR 1.64–2.45 mL/kg). The difference between set and delivered tidal volume was <0.2 mL/kg for 83% of time. In the individual recordings, the median VThf ranged between 1.44 and 3.31 mL/kg. During HFOV-VG, the VThf varied from 1 second to another, but it was very close to the target value when averaged over 5 min periods. After weight correction, the VThf or the diffusion coefficient of carbon dioxide (DCO2) showed weak inverse correlation with partial pressure of CO2(pCO2) (for VThf, r=−0.162, 95% CI −0.282 to –0.037, p=0.01). Uncorrected values showed no correlation. Of the 53 blood gas measurements taken when VThf was >2.5 mL/kg, there were only six (11%) with a pCO2 >8 kPa.
Conclusions During HFOV-VG, the tidal volume of oscillations varies in the short term but is maintained very close to the target over the longer term. VThf or DCO2 have poor correlation with CO2 levels but a volume of >2.5 mL/kg VThf is rarely needed.
- Mechanical Ventilation
- Volume-targeted Ventilation
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Contributors GB conceptualised and designed the study, collected the data, wrote the computer code and performed the computational data analysis. CJM assisted in data analysis and interpretation. GB and CJM wrote the manuscript together and approved the final manuscript as submitted.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement We would like to share the computer (Python) code used for data processing and analysis on the Github (https://github.com) code repository. We will upload the code and make it publicly available once when our paper is accepted for publication.