Elsevier

Clinics in Perinatology

Volume 28, Issue 3, 1 September 2001, Pages 547-560
Clinics in Perinatology

VOLUME-CONTROLLED VENTILATION: Variations on a Theme

https://doi.org/10.1016/S0095-5108(05)70106-8Get rights and content

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WHY USE VOLUME VENTILATION?

Over the last 30 years, clinicians have become accustomed to pressure-limited, time-cycled ventilation for treating respiratory failure in newborns. The reasons for the use of this mode include ease of use, low cost, and the assumption that pressure-limited ventilation decreases barotrauma because of the capability to control peak inspiratory pressure (PIP). This, however, is an oversimplification not supported by scientific evidence.3, 8, 9 For example, in a two-compartment lung model with

VENTILATOR DESIGN AND OPERATION

The term pressure-limited ventilation does not seem to pose any problem related to its understanding, but there is often confusion between volume-controlled and flow-controlled modes. It may be easier to use the term volume-controlled ventilation for both modes, because any breath that is directly flow-controlled is indirectly volume-controlled, and vice versa. The mode of ventilation can be conveyed in even more detail by stating the control and phase variables for both mechanical and

COMBINATION MODES OF VOLUME-AND PRESSURE-LIMITED VENTILATION

Volume and pressure-limited modes have certain putative disadvantages. Attempts have been made to combine the desirable features of both volume- and pressure-targeted ventilation. These modes, which include volume-assured pressure support (VAPS) and pressure-regulated volume control (PRVC) ventilation, guarantee a tidal volume chosen by the clinician. Although these modes are still in the investigational stages, they are based on good physiologic rationale and have the potential to be effective

VOLUME-ASSURED PRESSURE SUPPORT VENTILATION

This mode combines the advantages of pressure and volume ventilation on a breath-to-breath, basis and can be used with both assist-control and SIMV. It can be described as “variable flow, volume ventilation.” This is a blended mode with decelerating, nonlimited, variable flow and guaranteed tidal volume delivery. Spontaneous (triggered) breaths begin as pressure support breaths. The ventilator measures delivered volume when inspiratory flow has decelerated to the minimal set value. As long as

PRESSURE-REGULATED VOLUME CONTROL

This is a form of closed-loop ventilation that attempts to combine the features of volume control and pressure control.12 Essentially, the clinician sets a target tidal volume and a maximum pressure level. The ventilator attempts to achieve the volume target using a decelerating-flow gas delivery pattern at the lowest possible airway pressure. When activated, the first delivered breath is a test breath at 10 cm H2O pressure, which is used to calculate the patient's compliance. The next three

VOLUME-GUARANTEED PRESSURE-LIMITED VENTILATION

Volume guarantee is a feature that primarily ventilates with a time-cycled, pressure-limited breath type but allows the pressure to be increased to a user-adjustable maximum pressure setting to guarantee volume.11 Pressure may also be lowered with improving compliance. This is an autofeedback feature that guarantees tidal volume, but it is based on an 8- to 10-breath average, and is referenced to exhaled tidal volume. Volume-guarantee may be combined with assist-control, SIMV, and pressure

CLINICAL CONSIDERATIONS

Because volume-targeted modes of ventilation have become available for use in neonatal practice only recently, clinical trials are few, and much information can only be extrapolated from adult studies. In one of the first neonatal trials, 50 preterm babies weighing 1200 g or more with clinical and radiographic evidence of respiratory distress syndrome were randomly allocated to receive either volume-controlled ventilation or time-cycled, pressure-limited ventilation.14 Tidal volume delivery in

FUTURE DIRECTIONS

The development of microprocessor-based respiratory technology and sophisticated, yet miniature, transducers has enabled the development of new modes of volume-targeted ventilation for neonatal respiratory failure. This further expands the therapeutic range and enables customization of ventilator management based on specific pathophysiology and patient responses. Gone are the days when all neonatal lung diseases were treated alike.

The volume-controlled modes are new and represent a departure

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Address reprint requests to Steven M. Donn, MD Neonatal-Perinatal Medicine University of Michigan Health System F5790 C.S. Mott Children's Hospital 1500 East Medical Center Drive Ann Arbor, MI 48109-0254 e-mail: [email protected]

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