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Target volume settings for home mechanical ventilation: great progress or just a gadget?

Home mechanical ventilation (HMV) is a well-established treatment option for patients with chronic hypercapnic respiratory failure, whereby non-invasive positive pressure ventilation (NPPV) serves as the predominant means of HMV delivery.1 ,2 In general, there are two physiologically-different modes of NPPV deliveries, volume-preset NPPV and pressure-preset NPPV. During volume-preset NPPV a fixed inspiratory volume (Vinsp) is set at the ventilator, while the inspiratory positive airway pressure (IPAP) varies depending on airway resistance. Conversely, Vinsp varies during pressure-preset NPPV, while IPAP remains fixed. The advantage of volume-preset NPPV is that Vinsp, and hence tidal volume, are relatively stable; however, this can lead to a breath-by-breath variation in IPAP levels that can become a burden for the patient, and the leakages that regularly occur during NPPV are not compensated for. In contrast, the Vinsp that is delivered during pressure-preset NPPV may be unstable due to increased airway resistance; however, given that the variation in IPAP is lower, this is often better tolerated by the patient. In addition, leak compensation is provided by pressure-preset NPPV, as shown by in vitro3 and in vivo4 studies. In addition, ventilators providing pressure-preset NPPV are cheaper. Thus, pressure-preset NPPV has become the predominant means of delivering HMV. Nevertheless, randomised controlled trials have shown that volume- and pressure-preset NPPV generally have comparable effects on improvements in blood gases, sleep quality and health-related quality of life (HRQL),5 ,6 although pressure-preset NPPV is reportedly better tolerated due to fewer gastrointestinal side effects.5 However, clinicians should always weigh the advantages and disadvantages of the two different approaches on an individual patient basis.

Recently, the so-called hybrid modes have been developed to overcome the disadvantages of volume- and pressure-preset NPPV, respectively. …