Emergence of physiological rhythmicity in term and preterm neonates in a neonatal intensive care unit

Esmot Ara Begum,Makoto Obata,Motoki Bonno,Yoshihiro Komada,Masatoshi Kawai,Hatsumi Yamamoto

doi:10.1186/1740-3391-4-11

Esmot Ara Begum, Makoto Obata + Show 4 more

Open Access

https://doi.org/10.1186/1740-3391-4-11

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Abstract

BackgroundBiological rhythmicity, particularly circadian rhythmicity, is considered to be a key mechanism in the maintenance of physiological function. Very little is known, however, about biological rhythmicity pattern in preterm and term neonates in neonatal intensive care units (NICU). In this study, we investigated whether term and preterm neonates admitted to NICU exhibit biological rhythmicity during the neonatal period.MethodsTwenty-four-hour continuous recording of four physiological variables (heart rate: HR recorded by electrocardiogram; pulse rate: PR recorded by pulse oxymetry; respiratory rate: RR; and oxygen saturation of pulse oxymetry: SpO2) was conducted on 187 neonates in NICU during 0–21 days of postnatal age (PNA). Rhythmicity was analyzed by spectral analysis (SPSS procedure Spectra). The Fisher test was performed to test the statistical significance of the cycles. The cycle with the largest peak of the periodogram intensities was determined as dominant cycle and confirmed by Fourier analysis. The amplitudes and amplitude indexes for each dominant cycle were calculated.ResultsCircadian cycles were observed among 23.8% neonates in HR, 20% in PR, 27.8% in RR and 16% in SpO2 in 0–3 days of PNA. Percentages of circadian cycles were the highest (40%) at <28 wks of gestational age (GA), decreasing with GA, and the lowest (14.3%) at >= 37 wks GA within 3 days of PNA in PR and were decreased in the later PNA. An increase of the amplitude with GA was observed in PR, and significant group differences were present in all periods. Amplitudes and amplitude indexes were positively correlated with postconceptional age (PCA) in PR (p < 0.001). Among clinical parameters, oxygen administration showed significant association (p < 0.05) with circadian rhythms of PR in the first 3 days of life.ConclusionWhereas circadian rhythmicity in neonates may result from maternal influence, the increase of amplitude indexes in PR with PCA may be related to physiological maturity. Further studies are needed to elucidate the effect of oxygenation on physiological rhythmicity in neonates.

Highlights

Biological rhythmicity, circadian rhythmicity, is considered to be a key mechanism in the maintenance of physiological function
Preterm neonates hospitalized in a neonatal intensive care unit (NICU) face many challenges to adapt to the new environment
Neonates are deprived of maternal influences, which is essential for their development

Summary

Introduction

Biological rhythmicity, circadian rhythmicity, is considered to be a key mechanism in the maintenance of physiological function. About biological rhythmicity pattern in preterm and term neonates in neonatal intensive care units (NICU). It has been thought that this environmental condition may influence the development of biological rhythm in preterm neonates [4,5,6]. Many physiological processes are known to be cyclically organized [11] They show different cycles: circadian cycles last approximately 24 hours, ultradian cycles shorter than 24 hours, and infradian cycles longer than 24 hours [12]. These rhythms interact mutually as well as with the outside fluctuating environment under the control of feedback systems providing an orderly function that enables life [11]

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