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Advanced closed loops during mechanical ventilation (PAV, NAVA, ASV, SmartCare)

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New modes of mechanical ventilation with advanced closed loops are now available, and in the future these could assume a greater role in supporting critically ill patients in intensive care units (ICUs) for several reasons. Two modes of ventilation – proportional assist ventilation and neurally adjusted ventilatory assist – deliver assisted ventilation proportional to the patient's effort, improving patient–ventilator synchrony. Also, a few systems that automate the medical reasoning with advanced closed-loops, such as SmartCare and adaptive support ventilation, have the potential to improve knowledge transfer by continuously implementing automated protocols. Moreover, they may improve patient–ventilator interactions and outcomes, and provide a partial solution to the forecast clinician shortages by reducing ICU-related costs, time spent on mechanical ventilation, and staff workload. Preliminary studies are promising, and initial systems are currently being refined with increasing clinical experience. A new era of mechanical ventilation should emerge with these systems.

Section snippets

Why automated mechanical ventilation will be used in the future

There are now strong reasons to believe that automated mechanical ventilation will be used more and more in the future. It has been clearly shown that the patient's outcome in the ICU is directly linked to the staff workload.17, 18, 19, 20, 21 A marked increase in the use of mechanical ventilation is forecast*22, 23, 24, concurrent with a stagnation in the number of clinicians skilled in taking care of these patients (mainly intensivists, anaesthesiologists, pneumologists, and respiratory

Proportional assist ventilation (PAV)

This mode of ventilation was described only a few years after pressure support8, 9, and initially generated great enthusiasm. Numerous clinical studies were conducted, but so far PAV has failed to spread into daily practice. This mode of ventilation is available on several ventilators: PB 840 (Tyco, Carlsbad, CA, USA) and Evita ventilators as PPS (proportional pressure support) (Draeger Medical Inc, Lubec, Germany). Unlike PS ventilation, the pressure delivered to a patient with PAV is not

Neurally adjusted ventilatory assist (NAVA)

NAVA is a new mode of ventilation10 which has become available on the market only very recently, on Servoi ventilators (Maquet Critical Care, Solna, Sweden). As for PAV, the level of ventilatory assistance is proportional to the patient's effort (Fig. 1, Fig. 2), and the closed loop is within the cycle. Its main feature is that the signal used by the ventilator to deliver assistance is not a pressure signal (as for the usual ‘pneumatic’ ventilator) but the diaphragmatic electromyogram signal

Adaptive support ventilation (ASV)

This mode of ventilation is available on Galileo ventilators (Hamilton Medical, Bonaduz, Switzerland). ASV is a mode of ventilation which allows delivery of pressure cycles that may be assisted (PSV-like) or controlled (PC-like). The characteristics of the cycles delivered by the ventilator are related to a minute ventilation target set by the clinician and on automated measurements of the patient's respiratory mechanics.12 The working principles of this mode are based on the findings of Otis

NeoGanesh (SmartCare™)

This system allows automation of several tasks during the weaning phase, allowing an automatic adjustment of the level of assistance, and enacts a protocol to decrease the assistance and perform automated spontaneous breathing trials. This system of ventilation is not a new mode since it uses pressure support as primary mode, but thanks to the use of artificial intelligence, the closed loop used by the ventilator introduces a further degree of complexity. Indeed, this system can mimic the

Conclusion: in the future, the ventilators will adapt themselves to the patient and not the reverse

Traditional modes used for mechanical ventilation (pressure support ventilation, assist control ventilation in volume or in pressure) all operate with simple closed loops to define the cycles, but the rules of these loops are rigid, and the patient must adapt to these rules. The pressures or volumes delivered with these modes are fixed on the basis of the pressure and flow within the airways. The simplicity of these modes is probably the explanation for their success. Thanks to technological

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