Acoustic Analysis of Neonatal Breath Sounds: Changes during the Breath Adaptation Period.

Abstract

The breath adaptation period of newborns involves the switch from placental respiration to pulmonary respiration and remarkable respiratory-physiological changes. We made an acoustic analysis of the changes over time in neonate breath sounds as one of the objective indicators of such changes.Using 30 children delivered transvaginally and 11 children delivered by caesarean section as subjects, breath sounds were recorded 2, 6, 12, 24, 48 and 72 h after birth, and frequencies were analyzed by a fast Fourier transform. From the power spectrum obtained, the percentage of the high frequency power at 500-700 Hz to the total power at 100-700 Hz (hereafter referred to as %500-700) was calculated for the study. In the children delivered transvaginally, %500-700 reached a peak 24 to 48 h after birth and tended to decrease gradually thereafter. The children delivered by caesarean section showed a peak 48 to 72 h after birth in many cases, although no fixed trend was seen. Various factors determine the frequency characteristics of breath sounds. Our study suggests that not only the influence of the discharge and the absorption of vesicular fluid, but also the lung compliance and changes in the functional residual volume, are involved with the changes in the frequency characteristics of the breath sounds of newborns from the period immediately after birth through the breath adaptation period.