Infants born very preterm react to variations of the acoustic environment in their incubator from a minimum signal-to-noise ratio threshold of 5 to 10 dBA.

Kuhn, Pierre; Zores, Claire; Pebayle, Thierry; Hoeft, Alain; Langlet, Claire; Escande, Benoît; Astruc, Dominique; Dufour, André

INTRODUCTION Very early preterm infants (VPIs) are exposed to unpredictable noise in neonatal intensive care units. Their ability to perceive moderate acoustic environmental changes has not been fully investigated. RESULTS Physiological values of the 598 isolated sound peaks (SPs) that were 5-10 and 10-15 dB slow-response A (dBA) above background noise levels and that occurred during infants' sleep varied significantly, indicating that VPIs detect them. Exposure to 10-15 dBA SPs during active sleep significantly increased mean heart rate and decreased mean respiratory rate and mean systemic and cerebral oxygen saturations relative to baseline. DISCUSSION VPIs are sensitive to changes in their nosocomial acoustic environment, with a minimal signal-to-noise ratio (SNR) threshold of 5-10 dBA. These acoustic changes can alter their well-being. METHODS In this observational study, we evaluated their differential auditory sensitivity to sound-pressure level (SPL) increments below 70-75 dBA equivalent continuous level in their incubators. Environmental (SPL and audio recording), physiological, cerebral, and behavioral data were prospectively collected over 10 h in 26 VPIs (GA 28 (26-31) wk). SPs emerging from background noise levels were identified and newborns' arousal states at the time of SPs were determined. Changes in parameters were compared over 5-s periods between baseline and the 40 s following the SPs depending on their SNR thresholds above background noise.