By Betty Tran, MD, MSc
Assistant Professor of Medicine, Pulmonary and Critical Care Medicine, Rush University Medical Center, Chicago
Dr. Tran reports no financial relationships relevant to this field of study.
SYNOPSIS: In this single-center, randomized, clinical trial, among patients suffering from acute respiratory distress syndrome, the use of helmet noninvasive ventilation was associated with a reduction in intubation rates, ICU length of stay, and hospital and 90-day mortality.
SOURCE: Patel BK, Wolfe KS, Pohlman AS, et al. Effect of noninvasive ventilation delivered by helmet vs face mask on the rate of endotracheal intubation in patients with acute respiratory distress syndrome: A randomized clinical trial. JAMA 2016;315:2435-2441.
Previous work has shown a 51% failure rate of noninvasive ventilation (NIV) among patients suffering from acute respiratory distress syndrome (ARDS) who subsequently require endotracheal intubation.1 This is thought to be related to the inability to deliver high levels of positive end-expiratory pressure (PEEP) with a face mask due to patient intolerance and mask leak. In this study from the University of Chicago, Patel et al sought to determine whether NIV delivered via a helmet interface, which allows for increased titration of positive airway pressure without substantial air leak and improved patient tolerability, could reduce the need for endotracheal intubation in addition to improving other patient outcomes.
In this single-center, randomized, clinical trial, consecutive patients admitted to the adult medical ICU were screened for eligibility. Patients > 18 years of age who met Berlin criteria for ARDS and who required face mask NIV for at least eight hours were eligible for enrollment. The primary outcome was the proportion of patients who required endotracheal intubation based on a priori criteria, which included: neurologic deterioration, persistent or worsening respiratory failure (e.g., oxygen saturation < 88%, respiratory rate > 36 breaths/minute), intolerance of face mask or helmet, airway bleeding, or copious secretions. Secondary outcomes (which were considered exploratory) were 28-day invasive ventilation-free days, ICU and hospital length of stay, hospital and 90-day mortality, and adverse events.
Of the 740 patients admitted with acute respiratory failure requiring NIV, 83 were ultimately randomized: 39 to receive NIV via face mask and 44 to receive NIV via helmet. The authors ended the study early after meeting criteria for efficacy, but also based on work published at the time that suggested increased mortality among patients treated with face mask NIV compared to high-flow nasal cannula.2 Median time on NIV to randomization was not significantly different between the two groups. The intubation rate in the face mask group was 61.5% vs. 18.2% in the helmet group (absolute difference -43.3%; 95% confidence interval [CI], -62.4% to -24.3%; P < 0.001). In the exploratory secondary analyses, the helmet group experienced more ventilator-free days (28 vs. 12.5 days; absolute difference, 8.4; 95% CI, 13.4-3.4; P < 0.001), shorter ICU length of stay (4.7 vs. 7.8 days; absolute difference, -2.76; 95% CI, -6.07 to 0.54; P = 0.04), and lower hospital and 90-day mortality (hazard ratio, 0.51; 95% CI, 0.23-0.99; P = 0.047). Adverse events were few; three patients in the face mask group developed a nose ulcer, and three patients in the helmet group developed neck ulcers.
Although it featured a small number of enrolled patients because it ended early, this study suggests that a change in delivery interface could significantly influence the effect of NIV in patients with ARDS. Compared to patients receiving NIV via face mask, those randomized to NIV via helmet had higher median sustained PEEP levels (8.0 cm H2O vs. 5.1 cm H2O; P = 0.006) and were less tachypneic after randomization (24.5 breaths/min vs. 29.1 breaths/min; P < 0.001). The most common reason for intubation among patients in the face mask group was respiratory failure; in the helmet group, it was neurologic failure. The significant reduction in intubation rate among those receiving NIV via helmet and low rate of adverse events makes it an attractive option in this patient population. Although the study could not be blinded, use of a priori criteria to determine failure of NIV, as well as standard protocols to titrate and wean NIV, helped decrease bias.
There are a few other points worth mentioning. The study ended early and, as such, the magnitude of the effect seen may be exaggerated. Second, helmet delivery devices may not be available or commonly used in all hospitals, and proper training with regard to use and titration is needed to ensure the outcomes seen in this study can be reproduced. Finally, results from this study should not be used as overwhelming evidence for the role of NIV in ARDS. Enrollment of patients did not occur until they were receiving NIV for at least eight hours; although not reported by the authors, I suspect that a sizable number of patients admitted with acute respiratory failure due to ARDS were intubated before the eight-hour mark. Regardless, this study’s outcomes are intriguing, and further multicenter trials should focus on whether these findings can be replicated.
- Antonelli M, Conti G, Moro ML, et al. Predictors of failure of noninvasive positive pressure ventilation in patients with acute hypoxemic respiratory failure: A multi-center study. Intensive Care Med 2001;27:1718-1728.
- Frat JP, Thille AW, Mercat A, et al. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N Engl J Med 2015;372:2185-2196.