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February 28, 2013

High-Frequency Oscillation for Acute Respiratory Distress Syndrome.

Mazen Kherallah

Summarized by: 

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).

Any limitations?

  • 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.


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