High-frequency ventilation with the Dräger Babylog 8000plus: measuring the delivered frequency.
BACKGROUND
Ventilator frequency is one of the determinants of tidal volume delivery during high-frequency ventilation. Clinicians increasingly use data on ventilator displays to inform their decisions.


OBJECTIVE
To measure the frequencies delivered by the Dräger Babylog 8000plus ventilator when used in high-frequency mode.


METHODS
Ventilator waveforms using a test lung were recorded at the full range of settings 5-20 Hz using Spectra software at 1000 Hz. The changes in frequency produced by a 1-Hz change in set frequency were calculated. Actual and displayed frequencies were compared.


RESULTS
For settings up to 12 Hz, median (range) difference between set and delivered frequencies was 0 (-0.4 to +0.1) Hz. Above 12 Hz, delivered frequency varied by -0.3 (-1.9 to +0.3) Hz. For 1-Hz changes in frequency settings, in the range 5-12 Hz, 1-Hz changes produced a change in delivered frequency of 1.0 (0.6-1.4) Hz. Above 12 Hz, the corresponding changes were 0.7 (0-2.9) Hz. The ventilator displays the set frequency during operation rather than the delivered frequency.


CONCLUSIONS
At 12 Hz and below, the differences between set and delivered frequencies were relatively small compared with those at 13 Hz and higher. Above 13 Hz, the difference between set and delivered frequencies was up to 2.9 Hz. Some frequency setting changes did not result in a change in delivered frequency.
Wheeler
K I
KI
Royal Women's Hospital, Melbourne, Australia. kevin.wheeler@thewomens.org.au
Schmölzer
G M
GM
Morley
C J
CJ
Davis
P G
PG
D002138:Calibration / Q000592:standards; D003626:Data Display; D004867:Equipment Design; D004865:Equipment and Supplies, Hospital; D006612:High-Frequency Ventilation / Q000592:standards*; D006801:Humans; D007231:Infant, Newborn; D007363:Intensive Care Units, Neonatal; D013990:Tidal Volume; D012122:Ventilators, Mechanical / Q000592:standards*