Mechanical ventilatory support using positive-pressure breaths has been a mainstay of ICUs for several decades.<sup>6 American College of Chest Physicians Consensus Group Mechanical ventilation Chest 1993 ;  104 : 1833-1859

Cliccare qui per andare alla sezione Riferimenti</sup> Total ventilatory support generally attempts to duplicate the normal bulk flow ventilatory pattern and uses tidal volumes of 6 to 15 mL/kg, machine breath rates of 10 to 30 breaths/minute, and inspiratory-to-expiratory (I:E) ratios of 1:4 to 1:2. These positive-pressure breaths generally are delivered as flow-limited–volume-cycled or pressure-limited–time-cycled breaths.<sup>4 American Association for Respiratory Care Consensus Group Essentials of mechanical ventilation Respir Care 1992 ;  37 : 1000-1009

Cliccare qui per andare alla sezione Riferimenti</sup> Positive-pressure ventilatory support usually is used in conjunction with elevations in baseline (end-expiratory) pressure (PEEP) of 5 to 20 cm H₂O and supplemental oxygen (O₂). Partial ventilatory support has been developed in addition to total ventilatory support. Partial ventilatory support is designed for use in the actively breathing patient who is capable of doing some of the work of breathing on his or her own. Under those conditions, the ventilator provides only a portion of the work of breathing. Gradual reductions in partial support generally are used during the process of weaning from ventilatory support. Two fundamental approaches to partial support include intermittent use of flow-limited volume-cycle breaths or partial support of every breath using a pressure-limited flow-cycle breath.

During the past five decades, millions of patients throughout the world have received mechanical ventilatory support successfully. Nevertheless, there are limitations to current approaches that are important and that require new design features.<sup>5 American Association for Respiratory Care Consensus Group Assessing innovations in mechanical ventilatory support Respir Care 1995 ;  40 : 926-932

Cliccare qui per andare alla sezione Riferimenti, 49 Pierson D.J. Current limitations of mechanical ventilation Respir Care 1995 ;  40 : 933-940

Cliccare qui per andare alla sezione Riferimenti</sup> These limitations include: (1) current strategies are unable to provide adequate gas exchange in severely diseased lungs; (2) high airway pressures can overdistend healthier regions of the lung and cause a tissue injury and alveolar rupture; (3) an excessive fractional inspired oxygen (F io₂) can cause lung injury through oxygen toxicity; (4) if patient–ventilator interactions are not well matched, partial support modes can put unnecessary imposed workloads on patients' muscles; and (5) the cost and complexity of these devices remain high. Innovative strategies and new modes clearly are needed to address these issues.<sup>5 American Association for Respiratory Care Consensus Group Assessing innovations in mechanical ventilatory support Respir Care 1995 ;  40 : 926-932

Cliccare qui per andare alla sezione Riferimenti</sup>

In this article, several new strategies and modes are discussed. Three use capabilities available on most modern mechanical ventilators—“lung protection” strategies, long inspiratory time strategies, and enhancements in the use of pressure-limited breaths. Two additional strategies also are available clinically but only on special devices— airway pressure release ventilation and high-frequency ventilation. Finally, two new modes remain largely experimental, although clinical applications soon may be forthcoming—partial liquid ventilation and proportional-assist ventilation.