Temperature Instability Over Time and Respiratory Morbidity in the Very Premature Infant

Very premature infants are at risk for thermal instability due to thermoregulatory immaturity. Thermal instability upon neonatal intensive care unit admission has been associated with mortality and morbidity in these infants. Bronchopulmonary dysplasia (BPD), a developmental respiratory morbidity, is the most common complication of very premature birth. BPD is associated with admission temperature instability; however, its relationship with longitudinal temperature instability is poorly understood. An exploratory mixed-methods approach was used to examine the association between very premature infant temperatures over time and acute and chronic respiratory morbidities. The impact of daily care and respiratory care on infant body temperatures over time was also examined.

Research in the systematic literature review (Chapter 2) found that lower incubator temperatures can result in cold and dehumidified inspired air, and cold and dry inspired air can alter infant thermal stability. The studies in Chapter 3 and 4 found that infant temperatures (i.e., body, foot, abdominal-foot (temperature differential)) did not change significantly across the first five and 14 days of life, respectively. Daily care, respiratory care, and artificial respiratory support (i.e., MV, CPAP, RA) were associated with hypothermia. In addition, infants without chronic lung disease (CLD) had lower body temperatures and longer episodes of hypothermia compared to infants with CLD. Also, acute respiratory morbidities (i.e., bradycardia with desaturations and increases in supplemental oxygen and increased respiratory support) were associated with higher odds of hypothermia.

The relationships between hypothermia and both daily care and respiratory care support the need for bundling infant care, and potentially limiting care duration. The associations between hypothermia and respiratory support and acute and chronic respiratory morbidities should be explored further using advanced longitudinal methodologies. Ecological momentary assessment (EMA) can help delineate antecedent-consequence relationships to guide future intervention studies that are designed to reduce infant thermal instability over time and its associated morbidities.