Elsevier

Critical Care Clinics

Volume 23, Issue 2, April 2007, Pages 183-199
Critical Care Clinics

Pressure Control Ventilation

https://doi.org/10.1016/j.ccc.2006.12.005Get rights and content

As mechanical ventilators become increasingly sophisticated, clinicians are faced with a variety of ventilatory modes that use volume, pressure, and time in combination to achieve the overall goal of assisted ventilation. Although much has been written about the advantages and disadvantages of these increasingly complex modalities, currently there is no convincing evidence of the superiority of one mode of ventilation over another. Pressure control ventilation may offer particular advantages in certain circumstances in which variable flow rates are preferred or when pressure and volume limitation is required. The goal of this article is to provide clinicians with a fundamental understanding of the dependent and independent variables active in pressure control ventilation and describe features of the mode that may contribute to improved gas exchange and patient-ventilator synchronization.

Section snippets

Physiology of pressure control ventilation

PCV, unlike volume targeted modes, is pressure and time cycled and generates tidal volumes that vary with the impedance of the respiratory system. A working understanding of the factors that determine volume delivery is necessary for proper implementation of this mode of ventilation. During the inspiratory phase of PCV, gas flows briskly into the ventilator circuit to pressurize the system to a specified target. Once the target pressure has been reached, flow is adjusted to maintain a flat or

Determinants of tidal volume and minute ventilation

The tidal volume output that results from a given applied pressure and inspiratory time is predominantly influenced by flow resistance and respiratory system compliance [13]. If resistance to flow is high, the flow component of impedance is dissipated slowly over resistive elements, which results in small driving pressures across the circuit. Under these circumstances, pressure targets are reached at lower initial flow rates and must be maintained for longer periods of time to ensure

Theoretic advantages/disadvantages of pressure control ventilation

Interest in PCV and decelerating waveforms dates back several decades. Following the description of ARDS in the late 1960s, numerous animal studies were published that investigated the relative contribution of tidal volume, peak airway pressure, and end-expiratory pressure to ventilator-induced lung injury. These investigations, along with observational studies, suggested that high peak airway pressures were associated with macro- and microscopic barotraumas [8], [19], [20], [21]. PCV, by

Use of pressure control ventilation in various disease states

PCV has long been used in the setting of difficult-to-manage acute lung injury/ARDS. Clinicians have exploited the variable flow rates to improve patient work of breathing and limit high peak airway pressures. PCV also generally is associated with increased mean airway pressure, a ventilatory parameter found to correlate with oxygenation status. By delivering a larger proportion of the tidal volume early in the inspiratory phase, the lung is maintained at a higher volume, presumably recruiting

Summary

Despite its popularity, PCV has not been proved superior to other modes of mechanical ventilation. Although it is associated with lower peak airway pressures, the impact on lung mechanics, gas exchange, and risk of macro- and microscopic barotrauma is variable.

The adjustable flow rates and pressure limitations may prove useful in certain populations. Patients with high drive to breathe may enjoy a decreased work of breathing with PCV compared with VCV. In patients who have obstructive lung

Acknowledgments

The authors would like to thank Per Thorburg, MD, for his constructive review of the manuscript.

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