March 2002 / Volume 47 / Number 3 / Page 0296
The Role of Spontaneous Breathing During Mechanical Ventilation
IntroductionThe tremendous progress in microprocessor-driven ventilator technology over the last years has facilitated the introduction of a broad variety of different ventilatory modes into the clinical practice of mechanical ventilation. Many of these newer modalities are designed for partial ventilatory support, which might reflect the complexity of the issue of patient ventilator interactions when spontaneous breathing activity is present compared to controlled mechanical ventilation. There are reasons to believe that allowing some degree of spontaneous breathing activity during mechanical ventilation is useful not only to gradually withdraw ventilatory assistance in the process of weaning but also to avoid some of the adverse effects of mechanical ventilation in the early phase of acute respiratory failure when classically controlled modes of ventilation are used. It is the aim of this article to review the effects of preserved spontaneous breathing activity during mechanical ventilation with different ventilatory modalities in acute respiratory failure patients.
Advantages of Maintaining Spontaneous Breathing Efforts During Mechanical Ventilation
Clinical Course of Lung Injury
Ventilator-Associated Lung Injury
Ventilation Modes That Allow Spontaneous Breathing During Mechanical Ventilation
Synchronized Intermittent Mandatory Ventilation
Pressure Support Ventilation
Bi-Level Intermittent Positive Airway Pressure and Airway Pressure Release Ventilation
Proportional Assist Ventilation
Automatic Tube Compensation
The primary goal of mechanical ventilation is to restore gas exchange and to unload the patient from elevated work of breathing (WOB) during acute respiratory failure (ARF). To achieve these goals a broad spectrum of ventilatory modalities and strategies is already in use. Moreover, the development of microprocessor-driven mechanical ventilators has facilitated enormous progress in the implementation of different modes of ventilatory support in clinical use. Most of the newer ventilatory modes are designed for partial ventilatory support, reflecting the problem that different technologies might be used for patient ventilator interaction during assisted mechanical ventilation. However, the increasing use of partial support modalities is not only due to technologic improvements but also to data showing that avoiding controlled mechanical ventilation by preserving some spontaneous breathing activity of the diaphragm might be beneficial for gas exchange, hemodynamics, and the clinical course of acute lung injury. Herein we review the role of preserved spontaneous breathing activity during mechanical ventilation in ARF patients.