Bronchiolitis is an omnipresent entity for the pediatric intensivist. Pelletier et al (1), using the Pediatric Health Information System database found that between 2010 and 2019, PICU admissions for bronchiolitis doubled with nearly one-quarter of all bronchiolitis admissions in 2019 requiring PICU care. Over this same period, use of invasive mechanical ventilation was stable, but noninvasive ventilation (NIV) use increased nearly seven times, with one in ten children admitted to the hospital for bronchiolitis receiving NIV in 2019 (1). The observant practitioner will note that despite increasing NIV use, clear evidence that its use improves outcomes or reduces invasive mechanical ventilation requirements is lacking (1,2). Nevertheless, the use of NIV in the management of children with bronchiolitis is here to stay and focusing on improving how we use this supportive therapy is of utmost importance.

In a bilevel NIV mode, inspiratory positive airway pressure (IPAP) leads to reduction in the work through multiple mechanisms including augmenting inspiratory pressure and flow and decreasing inspiratory muscle effort (3). Logically, optimizing the patient-ventilator synchrony: receiving IPAP when the patient is inspiring should maximize these effects, is the key for bilevel NIV to be effective. The challenges of patient synchrony with NIV are well reported, especially with smaller children (4). Lung simulators have been used to demonstrate the superiority of dedicated NIV devices to detect triggering compared with ICU ventilators, even with a NIV mode (5). These devices, however, were not designed for children and this may not hold true at the lower flow rates, smaller tidal volumes, and higher respiratory rates of infants and toddlers. To overcome this limitation, the use of noninvasive neurally adjusted ventilatory assist (NIV-NAVA), with diaphragmatic muscle activity being used to detect triggering, is an attractive approach to increase the chance of patient-NIV ventilator synchrony.

In this issue of Pediatric Critical Care Medicine, the article by Lepage-Farrell et al (6) evaluates the use of NIV-NAVA in children younger than 2 years old admitted to an academic PICU for bronchiolitis that were judged by the clinical team to have failed “first tier respiratory support.” Failure criteria and respiratory support prior to NIV were not protocolized. The authors’ primary outcome was respiratory effort as determined by modified Wood Clinical Asthma Score (mWCAS) and peak inspiratory electrical diaphragmatic activity (Edi), a measure of the electrical activity of the diaphragm (7), with higher values having been used as surrogates for increased work of breathing (8). The mWCAS has previously been shown to have good inter-rater reliability for use of accessory muscle work, inspiratory breath sounds, and expiratory wheezing (9), all important components contributing to work of breathing. The authors reported decreases in both mWCAS and inspiratory peak Edi in the 2 hours after initiation of NIV-NAVA compared with preinitiation values. These findings led the authors to conclude that institution of NIV-NAVA reduced work of breathing for children with bronchiolitis that clinically failed conventional respiratory support. The authors believe that the key component of the reduction in work of breathing is the improvement in patient-NIV synchrony.

There are several shortcomings in the study by Lepage-Farrell et al (6). Their criteria for conventional NIV failure was not protocolized and left to bedside clinician’s judgment. As a result, patients were transitioned to NIV-NAVA from high-flow nasal cannula, continuous positive airway pressure, and bilevel positive airway pressure. Further, after transition to NIV-NAVA, children received significantly higher levels of IPAP. This increased driving pressure during inspiration may simply account for the improvements in work of breathing (10). Additionally, NIV-NAVA was delivered via full facemask. The minimization of leak with close attention to mask fit may also have contributed to decreased work of breathing.

The use of NIV for management of work of breathing in bronchiolitis is here to stay despite the lack of robust clinical evidence to improve meaningful patient outcomes. Now, our focus must be how we can provide safe, effective, and well-tolerated NIV. This is not an easy task as we must use devices often not intended but instead adapted to be used for NIV, or adult NIV devices that are not sensitive to the unique characteristics of small children using NIV for bronchiolitis. This can lead to difficulties in triggering and syncing for our smallest patients. The NIV-NAVA may potentially help address these limitations. However, not every center will have access to this technology, but that does not mean we cannot learn anything from the study by Lepage-Farrell et al (6). As we are uncertain whether improved synchrony by NIV-NAVA resulted in decreased work of breathing or if it was the higher IPAP and/or minimized mask leak that in fact improved work of breathing metrics. In other words, is the work of breathing reduction in fact just a case of when a little is not enough, try a little more?

To fully answer if NIV-NAVA is the best path forward for improving NIV management for bronchiolitis, we propose a future parallel design prospective study comparing conventional NIV protocolized escalation that includes transition to NIV-NAVA. Both arms would need to have clear observation periods and strict failure criteria. Additionally, to maximize clinical relevance, the study should not rely on work of breathing as the outcome of interest, but instead focus on length of respiratory support, ICU length of stay, adverse events during airway management, and duration of mechanical ventilation in children that fail NIV. We should continue to improve NIV in children, but single center, nonprotocolized, retrospective studies can only take the field so far. The time for thoughtful, protocolized trials is now!

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