Adjunctive ventilatory strategies have been developed to improve oxygenation or CO2removal during mechanical ventilation of critically ill patients. These techniques allow the clinician to attain clinical goals at lower levels of ventilatory support. These innovative techniques accomplish gas exchange external to the lungs (extracorporeal and intravenacaval gas exchange), augment alveolar ventilation by decreasing the physiologic dead space fraction of each tidal breath (tracheal gas insufflation), or administer therapeutic agents designed to improve the ventilation-perfusion matching of the lung (nitric oxide, surfactant replacement therapy, perflu-orocarbon-associated gas exchange, and prone positioning). At the current state of development, each of these adjuncts is promising. However, most lack solid clinical data defining their role in the care of critically ill patients.