Paper
Thursday, July 22, 2004
This presentation is part of : Critical-Care Nursing
Analysis of Heart Period Power in Ventilated Very-Low-Birthweight (VLBW) Infants Employing Growth Curve Techniques
Sandra Smith, PhD, APRN and Alexa Doig, RN, MS. College of Nursing, University of Utah, Salt Lake City, UT, USA
Learning Objective #1: Describe characteristics of heart period power in the low and high-frequency regions for ventilated preterm infants
Learning Objective #2: Identify applications of growth curve analysis in a variety of time series data
Background and Objectives: Heart period variability (HPV) is a sensitive measure of the balance between the parasympathetic and sympathetic branches of the autonomic nervous system (ANS) and is useful for determining an infant’s ability to adapt to external events. Spectral analysis of HPV provides a measure of high-frequency (HF) power representing parasympathetic tone and low-frequency (LF) power representing primarily sympathetic tone. The objectives of this project were to (1) identify normative characteristics of HF and LF power and (2) categorize patterns of intraindividual variability of HF and LF power over time.

Design and Variables: A secondary analysis of data derived from an experimental study comparing infant physiologic response to incubator care versus maternal holding was conducted. The original study was a two group crossover design with interrupted time series data collection. HF and LF power measured in ms2 were analyzed.

Sample: HPV data were collected from 16 mechanically ventilated VLBW infants in a metropolitan neonatal intensive care unit in the US. Infant mean corrected gestational age was 30.4 weeks (+/- 1.5), mean weight was 983.8 grams (+/- 209.7).

Analysis: Measures of central tendency and dispersion for HF and LF power were analyzed. Individual growth curve analyses are being generated to determine the pattern of change in ANS balance over time.

Findings: Mean HF power ranged from 5.13ms2 (+/- 2.85) to 6.83ms2 (+/-3.48) and mean LF power ranged from: 33.88ms2 (+/- 33.57) to 50.97ms2 (+/- 42.53) by gestational age groups. Results from the growth curve analyses will also be presented.

Implications: HPV may be a useful indicator of ANS maturation and response to environmental stressors. These findings will contribute to the body of knowledge of HPV and will serve as pilot data for a study of tailored interventions to promote parasympathetic maturation, growth, and restoration in these fragile infants.

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