NEGATIVE-IMPEDANCE VENTILATION AND PRESSURE SUPPORT VENTILATION - A COMPARATIVE-STUDY

Negative impedance ventilation (NIV) is a novel mode of assisted mecha nical ventilation (AMV) in which the pressure support is regulated to continuously track inspiratory flow and/or volume. In this study, we h ave evaluated the efficacies of NIV and inspiratory pressure support ( IFS) ventilation in a model of central airway obstruction in six rabbi ts. For both AMV modes there was an inverse relationship between the i ntrinsic work of breathing and alveolar pressure. Compared to IFS, NIV was found to: (1) achieve the same degree of ventilatory unloading an d similar level of pulmonary ventilation with considerably lower alveo lar pressure; (2) better restore the normal tidal volume and respirato ry frequency; (3) yield a shorter inspiratory duty cycle, thereby help ing to rest the respiratory muscles and preclude intrinsic positive en d-expiratory pressure. We conclude that NIV is more efficacious than I FS in negating airway obstruction and offers a better trade-off betwee n the risks of respiratory muscle fatigue and pressure induced complic ations. (C) 1997 Elsevier Science B.V.