Clinics in perinatology
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Extracorporeal membrane oxygenation was established as a standard of care by demonstrating its ability to save lives in moribund infants. The designs of early studies provided no living cohorts of similarly ill patients by which to measure accurately other (and perhaps to many more important) outcomes of interest: long-term neurodevelopmental outcomes or cost. Prospective cohort studies of neurodevelopmental outcomes post-ECMO demonstrate: (1) because ECMO, as used, saves lives, there will be an increase in the absolute number of handicapped children surviving; (2) there is little evidence that ECMO creates a relative increase in the percent of handicapped children surviving severe respiratory failure. ⋯ When such costs are compared with similar therapies in other fields (in such terms as cost per survivor), the cost of ECMO does not seem to be an outlier. Trials of newer therapies, such as iNO, show the capacity to decrease the use of ECMO but have failed to demonstrate either cost-effectiveness or better long-term outcomes. It has not been shown that either society or individual patients have benefited from the decreased need for ECMO.
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Proportional assist ventilation and respiratory mechanical unloading is a new mode of respiratory assistance that produces similar gas exchange with lower airway pressures than conventional ventilation in infants. This is achieved by tailoring the ventilator pressure contour to the specific derangements in lung mechanics and by a near perfect synchronization with the infant's own inspiratory effort. In contrast to conventional ventilation, PAV only amplifies the effect on ventilation of the spontaneous respiratory effort and relies on the subject's respiratory control. Whether PAV will reduce the incidence of acute complications and chronic pulmonary sequelae in infants needs to be evaluated in randomized controlled trials.
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Lung injury can be initiated at birth with the delivery room resuscitation. Adequate tidal volume must be achieved gradually and adjusted with each subsequent breath to achieve adequate, but not excessive, tidal volume delivery. Time constants vary greatly within the lung because some alveoli are collapsed, and some are inflated. ⋯ The best volume of inflation is achieved at the lowest pressure cost. Maintaining alveolar recruitment with the use of exogenous surfactant and positive end-expiratory pressure avoids alveolar collapse and injury with succeeding distending breaths. Although there have been significant advances in neonatal respiratory care, further improvement in outcomes may be expected by successfully avoiding ventilator-induced lung injury.
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Clinics in perinatology · Sep 2001
ReviewHypocapnia and hypercapnia in respiratory management of newborn infants.
Recent experimental and clinical data demonstrate that both hypocapnia and hypercapnia during the neonatal period may result in beneficial or adverse consequences. Multiple retrospective studies report a strong association between PaCO2 levels less than 25 to 30 mm Hg and an increased incidence of cystic PVL and CP in preterm infants. ⋯ A low tidal volume strategy combined with permissive hypercapnia is potentially a strategy that could prevent lung injury. Clearly, more randomized, controlled trials are needed before this latter strategy or that of permissive hypercapnia can be recommended routinely for preterm, near-term, or term gestation infants with respiratory disorders.
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Development of sophisticated transducers and microprocessor-based ventilators now enables the performance of volume-controlled ventilation of newborn infants. Volume-controlled modes include standard intermittent or synchronized intermittent mandatory ventilation; assist-control ventilation; and hybrid modes, such as pressure-support ventilation, pressure-regulated volume-control ventilation, volume-assured pressure support, and volume guarantee. This article describes the concepts and clinical applications of these ventilatory modes.