Background Prematurity and its respective comorbidities may result in longer periods of mechanical ventilation in intensive care units (ICU). A method for the assessment of organic maturity would be useful for this population. Heart rate variability (HRV), as an indicator of homeostasis, is a well-established tool for this approach. The objective of the study was to assess HRV in intubated preterm infants in ICU immediately prior to extubation and correlate HRV with clinical evaluation outcomes. Methods A total of 46 preterm infants, 13 (28.2%) males, were prospectively studied and divided into a group with failed extubation (FEG: n=11) and a group with successful extubation (SEG: n=35). HRV was evaluated in time, frequency and nonlinear domains with a Polar RS800 device. HRV measurements were assessed with Kubios HRV Premium Software and statistically analyzed with the StatsDirect Statistical Software, version 1.9.2015 (2002). P<0.05 values were considered as statistically significant. Results There were no significant differences between heart rate variables of failed and successful extubation when analyzing the total group. However, the analysis of the sub-group of preterm infants weighing less than 1000 g showed a clear differentiation between the groups, when the nonlinear variables (approximate entropy, sample entropy and multiscale entropy 1, 2 and 3) were used, demonstrating that the group with successful extubation shows greater complexity and, therefore, relatively greater autonomic stability. Conclusion HRV was effective in predicting failed extubation in preterm infants when evaluated in a nonlinear domain and in preterm infants weighing less than 1000 g.
Keywords: extubation; heart rate variability; nonlinear dynamic; preterm infants.