You're the Coach: A Guide for Parents of New Drivers, December 8, 2015

This publication is a guide for parents and guardians of teenagers learning to drive. It should be used with the Iowa Driver’s Manual to aid you in instructing your new driver about how to safely and responsibly operate a motor vehicle. Since the task of driving is affected by changing conditions, this manual does not attempt to cover all situations that may arise

Empirical mode decomposition approach to the estimation of cardiac baroreflex sensitivity in patients undergoing coronary artery bypass graft surgery

Cardiac baroreflex sensitivity (BRS) as assessed from spontaneous variability of heart period (HP) and systolic arterial pressure (SAP) is reduced during general anesthesia. Patients undergoing coronary artery bypass graft (CABG) surgery are characterized by a low BRS even before general anesthesia. These observations provide the basis of the difficulty in detecting the BRS reduction after the induction of general anesthesia in CABG patients. Empirical mode decomposition (EMD) is a technique decomposing the series into oscillatory modes at different time scales. We propose an EMD-based approach to the BRS estimate in 34 patients undergoing CABG. Results showed that the EMD-based method was not able to detect the BRS reduction in CABG patients after the induction of general anesthesia. The negative result was interpreted as a consequence of the inability of EMD-based method to account for HP-SAP causality

General anesthesia reduces the information exchange between heart and circulation

The study demonstrates the ability of an information-theoretic measure, such as the transfer entropy (TE), in detecting the depression of the cardiac baroreflex control and circulatory-cardio mechanical feedforward link during propofol-induced general anesthesia. TE was computed from spontaneous variability of heart period (HP) and systolic arterial pressure (SAP) in patients undergoing coronary artery bypass graft (CABG). TE from SAP to HP and from HP to SAP were evaluated by accounting for the confounding effect of respiration (R) affecting both HP and SAP (i.e. TESAP\u2192HP-R and TEHP\u2192SAP-R respectively). Both TESAP\u2192HP-R and TEHP\u2192SAP-R decreased during general anesthesia, thus suggesting that the strength of the causal relation diminished over both arms of the closed loop HP-SAP control. The squared coherence function between HP and SAP confirmed the decreased HP-SAP coupling during general anesthesia, even though it could not distinguish directionality

Towards the identification of subjects prone to develop atrial fibrillation after coronary artery bypass graft surgery via univariate and multivariate complexity analysis of heart period variability

The assessment of cardiovascular control complexity as derived from spontaneous heart period (HP) fluctuations can be improved by exploiting a multivariate (MV) approach. This work proposes the assessment of a normalized complexity index (NCI) of HP variability according to a k-nearest-neighbor approach based on local predictability performed in a MV nonuniform embedding space. The method allows the selection of the past components of HP, systolic arterial pressure (SAP) and respiration (R) most useful for the prediction of HP fluctuations. The NCI derived from the MV approach (NCIMV) was compared to a NCI computed via the same technique applied in a univariate (UV) embedding space (NCIUV) formed exclusively by HP past samples. Indexes were computed in 130 patients undergoing coronary artery bypass graft (CABG) surgery before and after the induction of general anesthesia. Thirty-eight subjects developed atrial fibrillation (AF) after surgery, while the remaining ones did not (noAF, n=92). Both NCIUV and NCIMV could separate AF from noAF patients and revealed a larger complexity of the AF subjects. However, the statistical power of the NCIMV was superior given that the probability of type I error was smaller than that of NCIUV. The assessment of cardiac control complexity could improve risk stratification of patients at risk of developing AF after CABG surgery

Cardiovascular interactions assessed via conditional joint transfer entropy in patients developing atrial fibrillation after coronary artery bypass graft surgery

Assigned the universe of knowledge \u3a9 as composed by one target and two exogenous signals, the conditional joint transfer entropy (CJTE), assessing the amount of information jointly transferred from the two sources to the target that can be uniquely linked to one of the two sources, was found useful to study cardiovascular control. We propose the assessment of CJTE from systolic arterial pressure (SAP) and respiration (R) to heart period (HP) conditioned on R (CJTESAP, R\u2192HPR) along the baroreflex, and from HP and R to SAP conditioned on R (CJTEHP, R\u2192SAPR) along the feedforward mechanical pathway, in 134 patients undergoing coronary artery bypass graft surgery before (PRE) and after (POST) the induction of general anesthesia. In this group 38 patients developed atrial fibrillation (AF) after surgery, while the remaining individuals did not (noAF, n=96). Both CJTESAP, R\u2192HPR and CJTEHP, R\u2192SAPR distinguished AF from noAF individuals in the PRE condition, suggesting an impairment of HP-SAP closed-loop regulation in AF group and the possibility to identify subjects at higher risk to develop post-surgery AF

Model-based directional analysis of cardiovascular variability identifies patients developing atrial fibrillation after coronary artery bypass grafting

Background: Postoperative atrial \ufb01brillation (AF) might be favored by cardiovascular control impairment. We hypothesize that cardiovascular regulation indexes derived from directional model-based analysis of the spontaneous \ufb02uctuations of heart period (HP) and systolic arterial pressure (SAP) can identify subjects at risk to develop AF after coronary artery bypass graft (CABG) surgery. Methods: Beat-to-beat HP and SAP series were derived from electrocardiogram (ECG) and invasive arterial pressure recorded for 5 min just before CABG surgery in conscious condition. The group comprised subjects who did develop AF (AF, n = 37, 71 \ub1 8 years, 27 males) or did not (noAF, n = 92, 65 \ub1 10 years, 85 males). From HP and SAP variabilities we computed classical time-domain, spectral, cross-spectral and complexity indexes characterizing autonomic function and cardiac barore\ufb02ex control. Moreover, we performed model-based directional analysis assessing the gain and strength of the relations from SAP to HP along cardiac barore\ufb02ex feedback and from HP to SAP along the feedforward pathway while disambiguating the effect of respiration as estimated from respiratory-related ECG modulations. Results: Classical HP and SAP variability indexes and barore\ufb02ex sensitivity could not separate AF from noAF individuals. Causality markers, and more speci\ufb01cally, the strength of the dynamical interactions from SAP to HP and vice versa, could distinguish the two groups: indeed, AFs have a lower degree of association from SAP to HP and vice versa. Conclusions: An impairment of the feedforward and feedback arms of the HP-SAP closed loop relation predisposes subjects undergoing CABG surgery to develop postoperative AF. Perspectives: Competency in medical knowledge: Atrial\ufb01brillation (AF) is a frequent complication after coronary artery bypass graft (CABG) surgery lengthening hospitalization duration and increasing healthcare system costs. Translational outlook 1: CABG patients who developed AF had a less preserved cardiovascular interactions due to less active physiological control mechanisms as resulting from the lower degree of dependence of systolic arterial pressure on heart period and vice versa before CABG surgery. Translational outlook 2: Cardiovascular control markers improve strati\ufb01cation of the AF risk after CABG surgery above and beyond more traditional demographic and clinical indexes

Stratifying the risk of developing atrial fibrillation after coronary artery bypass graft surgery using heart rate asymmetry indexes

Heart period (HP) asymmetry (HPA) is a peculiar pattern detectable over short-term HP variability recordings suggesting that cardiac deceleration runs are shorter than acceleration ones in healthy subjects. We tested the hypothesis that two traditional HPA indexes, namely the Porta's index (PI) and Guzik's index (GI), can distinguish patients scheduled for coronary artery bypass graft (CABG) surgery developing atrial fibrillation (AF) after surgery from the ones who do not (noAF). HP was derived from the electrocardiogram in 130 patients scheduled for CABG before (PRE) and after (POST) the induction of general anesthesia. PI assesses the percentage of positive HP changes, while GI quantifies the percent sum of the squared positive variations. Positive departures from 50 suggest that a series exhibits HPA. Surrogate analysis was exploited to assess the significant presence of HPA patterns. The likelihood of detecting HPA patters was higher in AF subjects and this result held during PRE. GI featured a greater statistical power than PI. Neither HP mean nor variance distinguished the two groups. HPA indexes can be exploited to improve stratification of the risk for post-surgery AF

Short-term multiscale complexity analysis of cardiovascular variability improves low cardiac output syndrome risk stratification after coronary artery bypass grafting

Background: Low cardiac output syndrome (LCOS) is a myocardial dysfunction leading to systemic hypoperfusion, favored by particular conditions of the autonomic nervous system. LCOS is one of the adverse events that might occur after cardiac surgery. Objective: The aim is to test the hypothesis that short-term multiscale complexity (MSC) analysis of heart period (HP) and systolic arterial pressure (SAP) variability series in the frequency bands typical of cardiovascular control could be fruitfully exploited in identifying subjects at risk of developing LCOS after coronary artery bypass graft (CABG). Approach: HP and SAP beat-to-beat series were derived from electrocardiogram (ECG) and invasive arterial pressure (AP) signal acquired in 128 patients scheduled for CABG before (PRE) and after (POST) the induction of general anesthesia with propofol and remifentanil. Subjects were labeled as LCOS (n = 14) and noLCOS (n = 114) according to the LCOS development. MSC markers were calculated as the complement to 1 of the modulus of the average position of the poles dropping in the low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, 0.15-0.5 Hz) bands as derived from the autoregressive model of HP and SAP series. Traditional time and frequency domain indexes were also calculated. Main results: Traditional parameters were able to assess the depression of the cardiovascular regulation induced by general anesthesia, but showed weak performances in differentiating LCOS and noLCOS groups. Conversely, HP complexity in LF band and SAP complexity in HF band assessed during POST remained associated with LCOS even after entering a multivariate logistic regression model adjusted for clinical and demographic factors. Significance: The MSC approach can be fruitfully applied to improve risk stratification for LCOS after CABG likely because MSC markers describe the dysfunction of the sympathetic control and the impairment of the mechanical properties of the heart in the LCOS group