Closing the loop of mechanical respiratory support for preterm infants

Premature infants require mechanical respiratory support to maintain adequate gas exchange, which consists of positive pressure ventilation and supplemental oxygen. However, the needed respiratory support often contributes to lung injury and other morbidity. Clinicians reduce the support to avert lung injury due to excessive and/or repeated lung inflation and oxygen toxicity. However, weaning is often delayed by fluctuations in ventilation and oxygenation due to instability of the respiratory system and spontaneous respiratory drive.;This work included the development of a system for closed loop targeted minute ventilation (V'E) continuously that adjusts ventilator frequency to maintain a desired ventilation level, a system for closed loop targeted tidal volume (VT) that adjusts the ventilator pressure to generate a desired tidal volume, and a third controller that results from the combined application of these controllers in parallel.;This work also involved development of a system for oxygenation targeted closed loop control of the fraction of inspired oxygen (FiO2). This system maintains oxygenation within an adequate range during fluctuations in oxygenation with the least FiO2.;A clinical study showed the efficacy of closed loop targeted V 'E in reducing the ventilatory support, without adverse effects on gas exchange in a group of premature infants compared to conventional mechanical ventilation.;In an animal study, closed loop targeted V' E and closed loop targeted VT were shown to be effective in maintaining ventilation and oxygenation in a rabbit model of apnea, reduced lung volume and respiratory system compliance. In this study, the combined controller was more effective than the individual components.;A clinical study demonstrated the efficacy of the system for oxygenation targeted closed loop FiO2 control in maintaining oxygenation in a group of ventilated premature infants who presented with frequent and acute episodes of hypoxemia.;In summary, this work documented the feasibility of closed loop control of mechanical respiratory support for premature infants. These techniques were effective in reducing the support and in maintaining ventilation and oxygenation by adapting to the changing needs of premature infants. This form of support may reduce the risk of lung injury and oxygen toxicity.