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 (DCO) showed weak inverse correlation with partial pressure of CO(pCO) (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 pCO >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 DCO have poor correlation with CO levels but a volume of >2.5 mL/kg VThf is rarely needed.