Pressure and volume modes of mechanical ventilation have been available for many years but not as options on the same ventilator until the early 1980s.<sup>21 Colice G.L. Historical perspective on the development of mechanical ventilation Principles and Practice of Mechanical Ventilation New York: McGraw-Hill (1994).  1-35

Cliccare qui per andare alla sezione Riferimenti</sup> The clinician now is faced with many choices when managing a mechanically ventilated patient. This article provides basic information on flow-limited, volume-cycled ventilation (VCV) and pressure-controlled ventilation (PCV) so comparisons and contrasts can be made between the two modes. The authors also review recommendations and potential problems commonly encountered when converting from one mode to the other. A good working understanding of volume and pressure modes of ventilation should allow the clinician to transfer from one mode to the other without difficulty. The final section of this article reviews some of the pertinent clinical studies and recent direct comparisons of VCV and PCV.

Although many of the principles discussed pertain to positive-pressure ventilation in general, this article focuses on assist-control VCV and PCV (pressure preset). It is flow that is controlled and cycled in VCV, but for the sake of simplicity, the authors refer to it as VCV. Aside from PCV, pressure modes of ventilation include pressure support and airway pressure release ventilation.<sup>24 Downs J.B., Stock M.C. Airway pressure release ventilation: A new concept in ventilatory support Crit Care Med 1987 ;  15 : 459-461

Cliccare qui per andare alla sezione Riferimenti, 73 Stock M.C., Downs J.B., Frolichter D.A. Airway pressure release ventilation Crit Care Med 1987 ;  15 : 62-66

Cliccare qui per andare alla sezione Riferimenti</sup> In addition, several options exist for combination modes (i.e., synchronized intermittent mandatory ventilation with pressure support) as well as several newer ventilatory modes available on the latest generation of mechanical ventilators (i.e., pressure-regulated volume control, volume-assured pressure support, and volume support). These modes attempt to combine the most desirable features of volume-based and pressure-based ventilation.<sup>40 MacIntyre N.R., Gropper C., Westfall T. Combining pressure-limiting and volume-cycling features in a patient-interactive mechanical breath Crit Care Med 1994 ;  22 : 353-357  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup>

The primary difference between PCV and the more commonly used VCV is that clinician-set inputs and measured outputs are exchanged. PCV does not deliver a predetermined tidal volume (V_T) but applies and maintains a set airway pressure throughout inspiration for a prescribed length of time. V_T is set in VCV and pressures are measured; in PCV, pressure is set and volume is measured. The measured outputs in both modes are governed by the impedance characteristics of the respiratory system (resistance and compliance) and the ventilator settings (i.e., frequency, inspiratory time).