Pressure Control Ventilation
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.
References (63)
ACCP Consensus Conference: mechanical ventilation
Chest
(1993)- et al.
Clinicians' approaches to mechanical ventilation in acute lung injury and ARDS
Chest
(2001) - et al.
Pressure-controlled and volume-cycled mechanical ventilation
Clin Chest Med
(1996) - et al.
Pressure-control ventilation in ARDS: a practical approach
Chest
(1997) - et al.
Effect of inspiratory time on tidal volume delivery in anesthesia and intensive care unit ventilators operating in pressure control mode
J Clin Anesth
(2005) - et al.
Effects of short-term pressure-controlled ventilation on gas exchange, airway pressures, and gas distribution in patients with acute lung injury/ARDS: comparison with volume-controlled ventilation
Chest
(2002) - et al.
Randomized trial comparing pressure-controlled ventilation and volume-controlled ventilation in ARDS
Chest
(2000) - et al.
Improved oxygenation and lower peak airway pressure in severe adult respiratory distress syndrome: treatment with inverse ratio ventilation
Chest
(1986) - et al.
Pressure controlled inverse ratio ventilation in severe adult respiratory failure
Chest
(1988) - et al.
The outcome of early pressure-controlled inverse ratio ventilation on patients with severe acute respiratory distress syndrome in surgical intensive care unit
Am J Surg
(2002)