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Congenital obstruction of the upper or lower airway jeopardizes immediate resuscitation of the neonate. Performed in conjunction with a scheduled cesarean delivery, the ex utero intrapartum therapy (EXIT) procedure involves exposing and partially externalizing the fetus without disturbing the feto-placental circulation. By preserving placental support, the EXIT procedure allows time for life-saving interventions, such as laryngoscopy, bronchoscopy, endotracheal intubation, tracheostomy, tumor decompression or resection, administration of medications and surfactant, and cannulation for extracorporeal membrane oxygenation. The EXIT procedure demands close cooperation among multidisciplinary teams caring for the parturient and the fetus. Intraoperative deep uterine relaxation to facilitate intrapartum fetal intervention must give way to rapid uterine contraction after delivery to prevent uncontrolled maternal hemorrhage. The fetus may be monitored intraoperatively using echocardiography and pulse oximetry. Changes in fetal condition must prompt immediate investigation of potential maternal, uteroplacental and fetal causes. The advantages and disadvantages of different anesthetic approaches are discussed. [ABSTRACT FROM AUTHOR]

This chapter surveys empirical models of market structure. We pay particular attention to equilibrium models that interpret cross-sectional variation in the number of firms or firm turnover rates. We begin by discussing what economists can in principle learn from models with homogeneous potential entrants. We then turn to models with heterogeneous firms. In the process, we review applications that analyze market structure in airline, retail, professional, auction, lodging, and broadcasting markets. We conclude with a summary of more recent models that incorporate incomplete information, "set identified" parameters, and dynamics. [ABSTRACT FROM AUTHOR]