A neonatal intensive care unit, usually shortened to NICU (sometimes pronounced "Nick You") and also called a newborn intensive care unit or intensive care nursery (ICN), is a unit of a hospital specializing in the care of ill or premature newborn infants. The NICU is distinct from the special care nursery (SCN) in providing a high level of intensive care to premature infants while the SCN provides specialized care for infants with less severe medical problems. NICUs were developed in the 1950s and 1960s by pediatricians to provide better temperature support, isolation from infection risk, specialized feeding, and access to specialized equipment and resources. Infants are cared for in incubators or "open warmers." Some low birth weight infants need respiratory support ranging from extra oxygen (by head hood or nasal cannula) to continuous positive airway pressure (CPAP) to mechanical ventilation. Public access is limited, and staff and visitors are required to take precautions to reduce transmission of infection. Nearly all children's hospitals have NICUs, but they can be found in large general hospitals as well. A NICU is typically directed by one or more neonatologists and staffed by nurses, nurse practitioners, nursery nurses, physician assistants, resident physicians, fellows, and respiratory therapists. Many other ancillary services are necessary for a top-level NICU. Other physicians, especially those with "organ-defined" specialties often assist in the care of these infants.