The art of weaning patients who have been in respiratory failure is to wean them in a timely manner without risk and to ensure that they remain successfully weaned. Various techniques of weaning are described that serially measure respiratory parameters and reduce ventilatory support in a controlled manner to ensure a safe and successful wean.” These currently used techniques are time and labor intensive. The weaning criteria and methods used have to be modified depending on each patient’s underlying disease process and ability to overcome a reduced compliance and/or an increased airway resistance. Unless close attention is paid to the patient during the weaning process, the patient could be stressed by the procedure and placed at risk. Recent developments in ventilator and computer technology have made closed loop control of ventilation feasible, and have the potential to make ventilation and weaning more comfortable and safer. Although computers have recently been used to improve the task, the implemented protocols adhere to the conventional clinical approach: weaning is considered to be a task that can be done by the machine and the patient will follow if he is weanable. review
Adaptive lung ventilation provides a new method of weaning for two reasons: it is patient centered and it is closed loop controlled. The basic concept of the ALV controller is to accommodate the patient’s breathing activities while maintaining a preset gross alveolar ventilation irrespective of the respiratory activities of the patient. If the patient is able to perform more ventilation relative to what the preset value is, the ALV controller will gradually reduce the pressure support down to a minimum of 5 cm H2O above PEEP and the ventilator rate to a minimum of 4 breaths/min. The 5-cm H2O minimum is to compensate for the resistance of the endotracheal tube and the imposed work of breathing of the circuit, while the four breaths/min minimum is a safety measure to prevent inadvertent apnea periods of longer than 15 s. Unlike other forms of ventilatory support, ALV reacts to patient activity. In pressure support ventilation, for example, an increase in patient effort increases the Vt yet does not reduce the ventilatory support.