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I. Importance of environment
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The fetus in a uterus without amniotic fluid, the infant with a nonsupportive home environment, and animals with atypical sensory experiences will exhibit behaviors that are atypical and are related to their environmental experience. The uterus typically provides a rich, appropriate environment for development. Following the delivery of a preterm infant, often as early as 23 weeks' gestation, the environmental stimulation changes dramatically. The environment and stressors of the NICU are in stark contrast to the ideal intrauterine environment, thus the NICU plays a major role in determining the neurodevelopment of preterm infants (Table 43-1). Modifications to provide a healing environment include physical, sensory, and caregiver stimulation and interactions.
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Patterns of infant development
Environments atypical for developing organisms are known to alter developmental outcomes. Because the NICU environment is so unlike the fetal or healthy, term newborn environment, an infant's development can be temporarily or permanently altered by this environmental stimulation. The developing nervous system “expects” certain stimulation to be provided by the environment at the specified time it is needed. Neuronal development occurs when the fetal brain is exposed to the expected experience at just the right time. If the expected experience occurs too early or too late, variations in the development of neuronal patterning or nerve growth and connections occur. The onset of sensory system functioning occurs in an invariant sequence across vertebrate species beginning with tactile, and then vestibular, chemical, auditory, and lastly visual (Figure 43-1). Unexpected stimulation can alter, hinder, or facilitate development of the sensory system.
Sleep development
Preterm infants have immature state organization that remains different from their term counterparts well past the neonatal period. The NICU environment can either facilitate or inhibit the development and organization of infant sleep. In addition, infant neurological development is related to the sleep and waking state organization. Therefore, promotion of normal sleep and waking behaviors is felt to be important to short- and long-term infant development. Careful observations of an infant's physiologic parameters and behaviors to assess sleep and waking states allow caregiving activities to be personalized to the infant's needs. Table 43-2...