Heart Rate Variability Analysis During Weaning from Mechanical Ventilation: Models for Prediction of the Weaning Trial Outcome Vessela Krasteva 1 , Mikhail Matveev 1 , Irena Jekova 1 , Georgi Georgiev 2 1 Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria 2 Pirogov University Emergency Hospital, Sofia, Bulgaria Abstract This study estimates the activity of the autonomic cardiac control (ACC) in patients undergoing weaning from mechanical ventilation, aiming to predict the weaning outcome. ECG and AVEA ventilator data from 13 successfully and 14 unsuccessfully weaned patients were collected. Heart rate variability (HRV) profiles were estimated in non-sedated patients during 2 weaning phases: (1) PSV - pressure support ventilation at 12-25 cmH 2 O; (2) SBT – spontaneous breathing trial at 8 cmH 2 O. HRV indices in the time- and frequency-domain were analyzed on 5-min RR-interval episodes under stationary conditions during each weaning phase. Our model for prediction of the successful weaning outcome considers 3 basic mechanisms for adequate ACC response on the weaning cardio-respiratory stress: (1) preserved ACC ability to maintain physiological adaptation; (2) modulated ACC activity by the breathing model; (3) mostly neurohumoral regulation of the blood circulation. The successful group model exhibits reduced total activity (TP, SDNN) with increased sympathetic (VLF/TP, LF/HF>1) and reduced vagal tone (HF/TP, RMSSD, pNN50), the latter correlated to the respiratory rate and tidal volume. Deviations from this HRV model are indicative for weaning failure detected with accuracy 92.6% (PSV), 81.5% (SBT), 96.3% (SBT-PSV). 1. Introduction Mechanical ventilation (MV) of critically ill patients is associated with many risks and complications that lead to high morbidity, mortality, longer intensive care unit stay, and higher treatment costs [1]. Identifying the patient's readiness at the earliest time possible for successful weaning from MV is the primary target for patients with command breathing [2]. Discontinuation from MV is the process for a gradual reduction in ventilator support, to allow patients the ability to assume increasing levels of work to breathe until sustain spontaneous breathing. This weaning process occupies an average of 40% of the total duration of mechanical ventilation, with failure in over one third of MV patients. The consolidated evidence- based clinical practice guidelines of the American Thoracic Society (ATS) and the American College of Chest Physicians (CHEST) point out the process of MV liberation as an investigation priority [1]. Weaning from MV has impact on the cardiovascular function by 3 physiological mechanisms [3-6]: 1) Changes in the oxygen transport (hypoxia), which may provoke circulatory disturbances with a terminal result of weaning failure or other fatal complications (acute myocardial infarction, heart failure and cardiogenic pulmonary edema, rhythm disorders). 2) Haemodynamic alterations as a result of changes in the intrathoracic pressure (ITP), which is positively dependent on the tidal volume and modulated by MV breathing cycles [6]. The associated changes in the cardiac output, ventricular preload and afterload may result in acute alterations of cardiac mechanics and myocardial ischemia, manifested as arrhythmias. 3) Effects on the autonomic nervous system (ANS) activity, which is influenced by humoral changes in the intrathoracic cardiovascular system due to ITP changes. Therefore, ANS tries to compensate for these humoral changes by two mechanisms – increasing the sympathetic tone and decreasing the parasympathetic tone that affects the heart rate. Heart rate variability (HRV) is the physiological phenomenon of inter-beat interval variation due to the joint action of the sympathetic and parasympathetic parts of the autonomic cardiac control (ACC) [7]. A number of studies on HRV changes at different phases during MV discontinuation have concluded that ACC status provides essential information on the pathophysiological imbalances reflected in the success or failure of weaning [3-5,8-14]. In failure patients, reduced HRV and vagal tone withdrawal have been reported [9,10,12]. This study aims to derive models for prediction of the weaning outcome by HRV, breathing and metabolic features, and to better understand the ACC role during MV weaning. Computing in Cardiology 2018; Vol 45 Page 1 ISSN: 2325-887X DOI: 10.22489/CinC.2018.113