The New England Journal of Medicine: Use Caution with HFOVs Systems

The New England Journal of Medicine says that high-frequency oscillatory ventilation systems—HFOVs—might not provide originally hoped-for benefits to certain patients.

HFOVs use small so-called “tidal” or lung volumes at an increased rate of respiration; however, trials revealed that instead of minimizing injuries, HFOVs could have caused harm in infants with acute respiratory distress syndrome (ARDS), said The New England Journal of Medicine.

While mechanical ventilation has long been believed to be life sustaining for critically ill patients, data the Journal described as “compelling” reveal that mechanical ventilation can be damaging to the lung in the event the ventilator is not set appropriately.

Should an inappropriate setting be used, excessive tidal volumes can stretch the patient’s lung, which can cause over-distention of the lung and further lung injury. Also, an insufficient positive end-expiratory pressure (PEEP) can prompt repetitive alveolar collapse followed by reopening, a condition which can lead a lung injury known as atelectrauma, the Journal explained.

Two major, multi-center, randomized trials that were reported in Journal discussed HFOV strategies. The Oscillation for Acute Respiratory Distress Syndrome Treated Early (OSCILLATE) trial found that an HFOV strategy with high mean airway pressures led to more deaths than did a traditional mechanical-ventilation strategy that used relatively high PEEP levels. In fact, the 47 percent in-hospital mortality—versus 35 percent in the control group—led to early termination of the study, said the Journal. The study found that the poor outcomes were likely linked to hemodynamic (blood movement) compromise.

In the Oscillation in ARDS (OSCAR) trial, the research team found no major difference in the outcome between an HFOV strategy and usual care with conventional mechanical ventilation. A similar rate of death from any cause at 28 days was 41.7 percent in the HFOV group and 41.1 percent in the usual-care control group. The hemodynamic compromise associated with HFOV was minimal in the OSCAR trial, likely due lower applied ventilatory pressures, a more pragmatic study design, and potential improved physician judgment and therapy individualized to each patient.

HFOV group participants in both trials received more sedatives and muscle relaxants than did control group participants, which might have “contributed to the disappointing outcomes,” said the Journal, which noted that both trials will help raise awareness about the broad and routine clinical use of HFOV.

The Journal pointed out that these data might suggest that HFOV protocols studied in the trials were ineffective, potentially worse, than usual care. Perhaps, said the Journal, patients diagnosed with ARDS should receive individualized therapy that considers the patient’s unique system, the cause of his/her disease, and the mechanisms that led to the lung injury.

Although significant conversation will occur concerning who should be included in the next trial and which technologies should be used, the Journal cautioned that clinicians should exercise care when routinely utilizing HFOV in ARDS patients.

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