February 28, 2013
High-Frequency Oscillation for Acute Respiratory Distress Syndrome.
What was the research question?
· Does high frequency oscillation ventilation improve mortality in patients with ARDS compared to conventional mechanical ventilation?
How did they do it?
A multicenter, randomized, controlled trial in 29 hospitals in England, Scotland and Wales.
795 patients with ARDS and PO2/Fio2 ratio <200, were randomized to undergo high frequency oscillation ventilation or conventional volume mechanical ventilation as per local practice (ARDSnet protocol was encouraged).
What did they find?
Primary endpoint was 30-day mortality was not different between the HFOV group and conventional group (41.7% versus 41.1%, P-0.85).
After adjustment for study center, sex, APACHE II score, and PaO2:FiO2 ratio by logistic regression, the odds ratio for survival in the conventional group, as compared with the HFOV group, was 1.03 (95% CI, 0.75 to 1.40; P=0.87).
Oxygenation improved in HFVO group on day 2 more than conventional group: PaO2:FiO2 on Day 2: 212 vs. 163.
There was no difference between HFOV and conventional patients in ventilator free days, ICU length of stay, or hospital stay.
Neuromuscular blocking agents were used for a longer duration with HFOV (2.5 versus 2 days, P2=.0 2).
There was no difference in days with inotropic or vasopressor agents between HFOV and conventional ventilation (2.9 versus 2.8 days, P=0.074).
Slow recruitment with high percentage of patients who were screened but not recruited (721.3%).
20 out of 29 centers had no prior experience with HFOV and had to be trained.
ARDSNet protocol was encouraged in conventional ventilation but not mandated.
The Novalung R100 ventilator is used in this trial (compared to SensorMedics 3100B in OSCILLATE trial), this ventilator was not used in prior clinical studies.
What does it mean?
Oxygenation improved but 30-day mortality was not different between the HFOV group and conventional group in moderate to severe ARDS (as per the new definition). However, the OSCILLATE trial reported a lower mortality in conventional ventilation likely due to the mandated use of ARDSnet protocol.
HFOV should not be used for routine ventilation in ARDS.