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.

1. 
   

   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.

   
   
2. 
   

   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 includes common behaviors of sleep and waking states.

1. 
   

   Intensive and convalescent care

   
   

   The light environment of the NICU must accommodate the needs of infants, families, and caregivers. Single infant family caregiving rooms provide the greatest flexibility with lighting; however, many nurseries lack single family room designs. NICUs must be able to maintain appropriate lighting for an infant and still meet the illumination needs for critical caregiving activities. Therefore, the light environment must be able to

   
   
   
   
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     Protect infant sleep.

     
     
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     Promote infant circadian rhythm development.

     
     
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     Maintain circadian rhythms and prevent affective seasonal disorders in families and caregivers.

     
     
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     Ensure safe delivery of care.

   
   
   
   
   1. 
      

      Light level recommendations in the NICU

      
      

      Infant bed spaces should have adjustable ambient lighting (background lighting) with a range of 10 to 600 lux or approximately 1 to 60 foot-candles. Adjustable light levels allow for individualization of light based on each infant’s needs for promotion of sleep, circadian rhythm development, and caregiving. Light levels should be measured in the horizontal plane at the infant’s bedside at the level of the infant.

      
      
   2. 
      

      Light Interventions in the NICU

      
      
      
      
      1. 
         

         Physiologic stability

         
         

         Protect infants’ eyes from direct bright electric or natural light exposure to avoid physiologic changes in heart rate or oxygenation levels. Maintain levels of ambient light below 600 lux when not needed for specific care procedures. Slowly increase light levels when a change in illumination is required, such as for procedures.

         
         
      2. 
         

         Circadian rhythm development and sleep-wake state organization

         
         

         Provide some daily exposure to light, preferably including shorter wavelengths to promote circadian rhythm development for infants ≥28 weeks’ postmenstrual age. It is unlikely that preterm infant’s circadian systems can take advantage of light exposure prior to 28 weeks’ PMA. The amount of daytime light necessary for the adequate entrainment of circadian rhythms is unclear, but daytime levels should not be <180 or >600 lux.

         
         

         Light levels should be kept low at night even when the infant awakes for feedings or caregiving. Avoid abrupt changes in illumination to avoid disturbance of infant sleep cycles. In addition to adjustable lighting fixtures, bassinet and incubator covers can be used to maintain night and daytime light levels.

         
         
      3. 
         

         Visual development

         
         

         Intense levels of light or flickering light can alter synaptogenesis in the visual system and should be avoided. Short periods of visual exposure to light in the melanopsin wavelength range are the only visual stimulation required for visual development prior to 39 to 40 weeks’ PMA.

   
   
2. 
   

   Follow-up care

   
   

   Following discharge, infants should be exposed to the natural variation of light according to the season; however, bright overhead lighting into the face should still be avoided. Parents should provide a lighted environment during the day and low light levels at night.

1. 
   

   Intensive and convalescent care

   
   

   Sound plays an important role in the emotional and auditory development of infants. Following preterm delivery, infants must rely on the experiences of the NICU to promote the development of infant language and later speech rather than the intrauterine sound environment. Intrauterine sounds are transmitted through amniotic fluid and are low in frequency. The unwanted sound of the NICU environment is characterized by unpredictable, disruptive, and physiologically stressful noise. These sounds are greater in intensity and at higher frequencies than infants experience in utero. The atypical sound experience of the NICU is felt to affect later language development, yet not all sound will produce a negative impact. Parents talking quietly to their infant during this critical time of brain development may facilitate auditory processing and language development.

   
   

   Preterm infants are also at risk for conductive and senorineural hearing loss, which can negatively impact expressive and receptive language development. Although it is unclear whether excessive noise in the NICU contributes to hearing loss, it is known that the children of women exposed to loud noise during pregnancy are at an increased risk for hearing loss. Low-birthweight infants have at least 20% failure rates on hearing tests. Poor auditory processing and speech and language delays also occur more frequently in children born preterm compared to term. The language delays in children born preterm are thought to be the result of the NICU experiences of these infants during a critical time of brain development. Therefore, the sound environment should

   
   
   
   
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     Protect the infant from intense, high frequency stressors.

     
     
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     Promote auditory processing and future speech/language development.

     
     
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     Minimize risk for hearing loss.

     
     
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     Ensure safe delivery of care.

   
   
   
   
   1. 
      

      Impact of noise in the NICU

      
      

      For caregivers, noise levels of the NICU can interfere with staff communication, attention to detail, and the ability to perform complex tasks required to care for critically ill infants (OSHA). For preterm infants, the repeated noise of the NICU interferes with sleep-wake cycles by increasing state arousals and body movements. With the cochlea functional at approximately 23 to 24 weeks’ gestation, preterm infants exhibit physiologic responses to sudden noise levels. Sudden changes in sound levels negatively impact infants by increasing heart rate, decreasing respiratory rate, and decreasing systemic and cerebral blood flow. These physiological changes may also result in decreased cerebral oxygenation. Noise levels >80 dB are thought to be associated with these physiologic changes because infants are unable to “tune out” or habituate to sounds from ventilators, alarms, telephones, pagers, and loud voices; all unpredictable and at various frequencies.

      
      
   2. 
      

      Decibel level recommendations in the NICU

      
      

      Decibel levels in NICU should not exceed an hourly average (Leq) of >45 dB and should not exceed 50 dB for more than 10% of each hour. Sound levels should not exceed for 1 second a max Leq of 65 dB. Noise levels in the NICU environment are reported to average between 70 and 117 dB and often exceed 100 dB during routine activity including noise made from ventilator equipment, alarms, and phones, closing the portholes of the incubator, placing items on top of the incubator, and conversations held close to the bedside.

      
      
   3. 
      

      Sound interventions in the NICU

      
      

      Unnecessary environmental noise can lead sound levels from 70 to >100 dB. Continuous background noise in the NICU may interfere with the infant’s ability to process auditory stimulation and may be associated with later language delays. While noise in the NICU cannot be eliminated, environmental design and modifications can facilitate noise reduction. Use of acoustical engineering techniques and single family rooms can also reduce environmental noise. Modifications of the bed space environment and decreasing ambient noise levels in the NICU can help decrease sound to levels that support rest and protect sleep. Regardless of the interior design of the NICU, ongoing monitoring of sound levels with plans to communicate findings to staff and families focuses on providing the quietest environment possible.

      
      
      
      
      1. 
         

         Alarms, telephones, and pagers

         
         

         Telephones, overhead paging systems and personal pagers should be eliminated as much as possible. If these modifications are not possible, the volume of telephones ring tones and overhead pages should be lowered and pagers should be set on vibrate. Silent alarm systems should be considered where reliable visual options exist. Silence ventilator and other alarms prior to interventions such as suctioning to prevent unnecessary noise. Respond quickly to alarms from cardiorespiratory monitors, infusion pumps, and pulse oximeters.

         
         
      2. 
         

         Equipment modifications

         
         

         Unnecessary noise from poorly designed equipment can increase sound levels in the NICU. Noise levels from respiratory equipment can be reduced by empting bubbling water from oxygen and ventilator tubing. Use plastic trash cans or add padding along the rim of metal trash cans. Replace running water faucets with a spray. Replace automatic paper towel dispensers with pull-down dispensers. Do not place items on tops of incubators or tap an incubator wall, as this has shown decibel levels from 70 to 95 dB.

         
         
      3. 
         

         Voice

         
         

         Conversational noise is at its highest level during caregiving rounds and during admissions of critically ill infants. Conversations and activities involved in an infant’s admission should occur away from the infant’s bed space as much as possible. Implementing a specific “quiet time” period can also reduce noise levels in some NICUs. During quiet times conversations, elective procedures, and bedside rounds should be avoided. Encourage staff to monitor and decrease the level of their own voices.

   
   
2. 
   

   Follow-up care

   
   

   Following discharge, infants continue their recovery from acute illnesses and some continue to deal with chronic illness. Parents should be educated on strategies to keep the home environment calm and quiet. Parents should be educated on the importance of protecting sleep to promote brain growth and development. Parents should also be educated to expect that their infant’s sleep patterns may change as they adjust to the home environment. The following list of strategies for the home should be shared with parents prior to discharge home.

   
   
   
   
   1. 
      

      Minimize noise levels near the infant by turning off loud appliances, which can reach decibel level >80 dB.

      
      
   2. 
      

      Provide a quiet time each day for the infant and other occupants of the household.

      
      
   3. 
      

      Talk softly and sing lullabies to the infant to soothe and promote language development.

      
      
   4. 
      

      Avoid loud or sudden sounds by silencing or minimizing phone ring tones.

      
      
   5. 
      

      Avoid background noise and conversations from across the room.

      
      
   6. 
      

      Limit the use of radios and do not place head phones on the infant.

      
      
   7. 
      

      Reconsider the use of toys that make music if an infant becomes agitated or disorganized.

      
      
   8. 
      

      Limit outings that are very noisy (grocery, sporting events, or social gatherings) during the first weeks at home if the infant is sensitive to noise. Decibel levels at these events can reach has high as 125 dB.

      
      
   9. 
      

      Offer music for transition to sleep, making sure to turn off music when infant is asleep. Place a “Baby Sleeping” sign on the house door so that visitors are aware that they will need to be quiet upon entering.