| Abstract | Mechanical ventilation is often required in the extremely small preterm infant because of
transient failure of the immature control of breathing system, chest wall instability, weakness
of the respiratory pump, and chronic lung disease. To better address some of these issues,
computer algorithms have been developed for continuous automated control of the arterial
hemoglobin oxygen saturation (by changing the fraction of inspired oxygen), of the tidal
volume (by varying peak inspiratory pressure), and of minute ventilation (by changing
respirator rate). Feasibility studies have shown that closed-loop computer control of
physiologic target variables may stabilize oxygenation, decrease the transpulmonary
pressure cost of ventilation, and expedite weaning from mechanical ventilation. In addition to
synchronizing the upstroke in ventilator pressure with the onset of the spontaneous
respiratory effort, computer technology may render the changeover from inspiration to
expiration patient-cycled in a mode called pressure support ventilation. Proportional assist
ventilation enhances ventilation in near perfect synchrony with the patient's spontaneous
respiratory efforts. With this mode, the clinician selects gains for elastic and/or resistive
unloading to tailor the ventilator pressure contour to the specific derangement in pulmonary
mechanics (restrictive and/or obstructive). Most of these newer ventilatory strategies are as
yet unproven and require randomized, controlled clinical study. Similarly, although on-line
pulmonary mechanics monitoring during mechanical ventilation has become available with
the adent of computer technology, its clinical utility is still not well established. |