Noninvasive ventilation (NIV) delivered by helmet (Sea-Long Medical Systems Inc.) significantly reduced the intubation rate compared with NIV delivered through an oronasal face mask in patients with acute respiratory distress syndrome (ARDS).
According to the results from this randomized controlled trial published in JAMA (2016;315:2435-2441), patients who used the helmet also had more ventilator-free days and significantly reduced ICU lengths of stay. The helmet (Figure) was so effective, in fact, that the trial was stopped early by the data and safety monitoring board.
“For patients with ARDS, treatment with helmet NIV was associated with significantly lower intubation rates and lower respiratory rate,” said John P. Kress, MD, of the Department of Medicine, Section of Pulmonary and Critical Care, at the University of Chicago Medicine. “There was also a statistically significant reduction in 90-day mortality with helmet NIV, which was a huge finding.”
As Dr. Kress explained, for more than 20 years, NIV with a face mask has been an effective strategy for acute respiratory failure due to chronic obstructive pulmonary disease (COPD). Studies also have shown clinical benefit for face mask NIV in managing acute cardiogenic pulmonary edema and for prevention in patients at risk for postextubation failure. However, minimal data are available on the efficacy of NIV in patients with ARDS.
Problems With Face Mask NIV
“Face mask NIV works wonderfully for COPD and for cardiogenic pulmonary edema,” Dr. Kress said, “but the mask interface doesn’t perform optimally at the higher pressures needed for patients with ARDS; the mask leaks, and it’s uncomfortable.”
More specifically, at higher levels of positive end-expiratory pressure (PEEP), face mask intolerance and air leak can impede effective oxygenation. In ARDS patients, face mask NIV fails about half the time.
On the other hand, with the helmet, a transparent hood that covers the entire head of the patient and has a rubber collar neck seal, higher levels of PEEP are possible. “We theorized that the helmet could essentially substitute for an endotracheal tube,” Dr. Kress said, “which was pretty much what we found.”
Between October 2012 and September 2015, 83 patients with ARDS requiring NIV delivered by face mask for at least eight hours were randomly assigned to continue face mask NIV or switch to a helmet for NIV support.
Although the researchers had planned enrollment of 206 patients (103 patients per group), early trial termination resulted in 44 patients randomly assigned to the helmet group and 39 to the face mask group.
Reductions in Mortality and Intubation Rates
As Dr. Kress reported, the intubation rate was 61.5% (n=24) for the face mask group and 18.2% (n=8) for the helmet group, a 43% absolute difference (P<0.001).
The number of ventilator-free days also was significantly higher in the helmet group (28) compared with patients who continued face mask NIV (12.5; P<0.001).
In addition, hospital and 90-day mortality were significantly lower in the helmet group than in the face mask group. At 90 days, 15 patients (34.1%) in the helmet group died compared with 22 patients (56.4%) in the face mask group.
Dr. Kress noted that decreased mortality and intubation rates were likely related. “If you can avoid getting intubated, your chances of dying are lower,” he explained. “That’s been the impetus behind noninvasive ventilation for the last 20 years.”
With just three interface-related skin ulcers for each group, the incidence of adverse events also was low.
Finally, at 8 and 5 cm H2O, respectively, the median PEEP was significantly different between the helmet and face mask groups, Dr. Kress said.
“Although we didn’t measure alveolar recruitment directly, we believe the helmet reduces respiratory distress,” Dr. Kress said. “When patients were switched from face mask to helmet, respiratory rate decreased by an average of 3 breaths per minute.”
Despite the success of the helmet with NIV, questions remain about the best treatment option. As Dr. Kress noted, a high-flow nasal cannula, which is more widely available, also has been proven effective in randomized controlled trials (N Engl J Med 2015;372:2185-2196). Moreover, although the face mask has largely moved out of favor, he is reluctant to discard the device entirely.
“I’m not sure I’m ready to throw the noninvasive face mask away, but I might be ready to throw it away in the setting of acute hypoxemic respiratory failure,” Dr. Kress said. “Certainly, in the future, I think we need to do more studies. How to design those studies, though, remains a work in progress.”
In an editorial (JAMA 2016;315:2401-2403), Jeremy R. Beitler, MD, MPH, of the Division of Pulmonary and Critical Care Medicine at the University of C alifornia, San Diego, and his colleagues noted that, while the helmet interface offers unique advantages that may influence efficacy of NIV, additional testing is needed.
“Clarification of appropriate eligibility criteria, optimal ventilator settings, and potential mechanisms of effect are needed before clinicians could consider an expanded role for helmet NIV in routine management of select patients with ARDS,” Dr. Beitler said. “Regardless, it is increasingly clear that there may be an important albeit underinvestigated role for some form of high-level noninvasive respiratory support to prevent intubation, and perhaps mortality, in acute hypoxemic respiratory failure.
“Whether helmet NIV affords benefit over high-flow nasal cannula warrants testing in a multicenter trial,” Dr. Beitler concluded.
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