RESUMO
OBJECTIVE: To evaluate the flexibility of respiratory behavior during spontaneous crying using an objective analysis of temporal measures in healthy neonates. PARTICIPANTS: A total of 1,375 time intervals, comprising breath cycles related to the spontaneous crying of 72 healthy, full-term neonates (35 females) aged between two and four days, were analyzed quantitatively. METHODS: Digital recordings (44 kHz, 16 bit) of cries emitted in a spontaneous, pain-free context were obtained at the University Children's Hospital Wurzburg. The amplitude-by-time representation of PRAAT: doing phonetics by computer (38) was used for the manual segmentation of single breath-cycles involving phonation. Cursors were set in these time intervals to mark the duration of inspiratory (IPh) and expiratory phases (EPh), and double-checks were carried out using auditory analyses. A PRAAT script was used to extract temporal features automatically. The only intervals analyzed were those that contained an expiratory cry utterance embedded within preceding and subsequent inspiratory phonation (IP). Beyond the reliable identification of IPh and EPh, this approach also guaranteed inter-individual and inter-utterance homogenization with respect to inspiratory strength and an unconstructed vocal tract. RESULTS: Despite the physiological constraints of the neonatal respiratory system, a high degree of flexibility in the ratio of IPh/EPh was observed. This ratio changed hyperbolically (râ¯=â¯0.71) with breath-cycle duration. Descriptive statistics for all the temporal measures are reported as reference values for future studies. CONCLUSION: The existence of respiratory exploration during the spontaneous crying of healthy neonates is supported by quantitative data. From a clinical perspective, the data demonstrate the presence of a high degree of flexibility in the respiratory behavior, particularly neonates' control capability with respect to variable cry durations. These data are discussed in relation to future clinical applications.
