Non‐invasive ventilation: Inspiring clinical practice

Abstract

The first reports of non-invasive positive pressure mask ventilation (NIV) for the management of hypercapnic respiratory failure began appearing in the late 1980s. Over the subsequent 30 years, the evidence for and use of NIV as a first-line ventilatory strategy to manage respiratory failure in patients with hypoventilation has grown significantly. However, with new knowledge and techniques also comes great clinical responsibility. It is crucial that clinicians recognize the potential not only for improved outcomes but also for the possibility of harm when NIV is used inappropriately or insufficiently. In the acute setting, evidence of benefit has been the strongest for patients presenting with acute hypercapnic exacerbations of chronic obstructive pulmonary disease (COPD) and cardiogenic pulmonary oedema, demonstrating significant reductions in morbidity, mortality and length of hospital stay. However, a number of issues around the safe and appropriate use of NIV have arisen. Although several large cohort studies have reported significant increases in NIV use for acute respiratory failure, utilization rates across institutions vary considerably, influenced by clinician familiarity with the technique, staff training and equipment availability. The importance of appropriate patient selection for NIV and the timing of such intervention cannot be overstressed. Large observational studies have shown that significant numbers of patients with COPD appropriate for NIV may not receive therapy, and conversely, a large proportion receiving NIV do not meet arterial blood gas criteria for it. The use of NIV in situations without a strong evidence base, such as pneumonia, hypoxaemic respiratory failure and asthma, is associated with a high likelihood of therapy failure. When NIV fails, and patients require escalation to invasive ventilation, outcomes are significantly poorer than in those managed successfully with NIV or who are intubated in the first instance. These findings highlight the importance of using NIV judiciously in the acute setting, not only to achieve the benefits seen from randomized trials but also to avoid the potential harms that can occur with its inappropriate use. Appreciating when not to use NIV is just as important as knowing when it should be used. Increasingly, patients with chronic hypercapnic respiratory failure are being managed with non-invasive ventilation in the home setting. The majority of these individuals will have a diagnosis of neuromuscular disease, obesity-related respiratory failure (e.g. obesity hypoventilation syndrome) or COPD. Although few randomized trials of NIV have been performed in patients with neuromuscular disorders, the available evidence supports its use to reduce symptoms and extend meaningful survival. However, the timing of intervention is of paramount importance in achieving these benefits. Obesity hypoventilation syndrome has become a major indication for home ventilation in many regions, although current evidence suggests many of these individuals may be effectively managed on continuous positive airway pressure therapy alone. There is little doubt that some form of positive airway pressure in this population is superior to no intervention in terms of improved gas exchange, relief of symptoms and improved quality of life. However, the impact on rehospitalization and mortality has received less attention in clinical trials. Early studies evaluating the use of NIV in stable hypercapnic COPD generally found limited or no evidence of benefit over oxygen therapy alone. Recent trials using higher levels of pressure support than previously reported have begun to provide a much needed evidence base to support the practice of using home NIV in this population. They have shown that in stable chronic hypercapnic COPD patients, addition of home nocturnal NIV aiming at lowering the partial pressure of arterial carbon dioxide level is associated with improved outcomes, including quality of life and survival, when compared to standard therapy. However, barriers to implementing this approach to NIV have been raised, including the time and resources needed to acclimatize patients to these high pressures and concern around tolerance to such pressures outside of clinical trials or limited expert centres. Recent advances in NIV device technology include automated ventilation algorithms and in-built monitoring software. These features provide clinicians with greater flexibility and choice around what modes of ventilation can best achieve the safe and effective delivery of NIV and how this can be readily assessed. Such advances are very welcome and have the potential to address some of the issues associated with conventional NIV, including patient access to therapy due to a lack of staff experienced in pressure titration and persistence of ineffective therapy related to insufficient monitoring capacity. However, whether the quality of ventilation and improvements in clinical outcomes are achieved have yet to be established. In this review series, clinical experts summarize and discuss the current evidence for the use of NIV across a range of disorders and clinical settings, addressing many of the issues, uncertainties and controversies outlined earlier. The authors provide insights into some