The relationship between physiological and behavioral measures of stress in preterm infants

The purpose of this exploratory descriptive analysis was to explore relationships among physiological stress, behavioral stress, and motor activity cues in preterm infants when they were not being handled or disturbed, and to determine whether there were differences between younger and older preterm infants in these variables or relationships.

The convenience sample included 42 preterm infants who had been 27 to 33 weeks gestational age at birth and were from 6 to 19 days old at the time of data collection in the neonatal intensive-care unit.

In each 10-minute observation, heart rate (HR) and oxygen saturation (O2 sat) levels were recorded every 5 seconds, and observational measures of behavioral distress and motor activity were recorded twice a minute. The physiological data were coded to reflect the percentage of each 10-minute period during which HR levels were less than 100 bpm or more than 200 bpm or O2 sat levels were abnormally low (less than 90 mg%). Data were analyzed with correlational and general linear mixed models procedures.

Stress cues and motor activity were more often related to low levels of O2 sat than to low or high HR. Physiological status was more often related to motor activity than to stress cues. Few differences in the relationships were observed between younger and older preterm infants.

Although these results are preliminary, they suggest that neonatal nurses should monitor preterm infants' behavioral stress and motor activity cues in response to caregiving and minimize stimuli that evoke stress responses linked to physiological instability.