Quantification of not-dipolar components of atrial depolarization by principal component analysis of the P-wave

Abstract

Abstract.Background. Principal component analysis (PcA) of the T-wave has been demonstrated to quantify the dipolar and not-dipolar components of the ventricular activation, the latter reflecting repolarization heterogeneity. Accordingly, the PcA of the P-wave could help in analyzing the heterogeneous propagation of sinus impulses in the atria, which seems to predispose to fibrillation. aim. The aim of this study is to perform the PcA of the P-wave in patients prone to atrial fibrillation (AF). Methods. PcA is performed on P-waves extracted by averaging technique from EcG recordings acquired using a 32-lead mapping system (2048 Hz, 24 bit, 0-400 Hz bandwidth). We extracted PcA parameters related to the dipolar and not dipolar components of the P-wave using the first 3 eigenvalues and the cumulative percent of variance explained by the first 3 Pcs (explained variance EV). Results and conclusions. We found that the EV associated to the low risk patients is higher than that associated to the high risk patients, and that, correspondingly, the first eigenvalue is significantly lower while the second one is significantly higher in the high risk patients respect to the low risk group. Factor loadings showed that on average all leads contribute to the first principal component.

Validation of a Simulink Model for Simulating the Two Typical Controlled Ventilation Modes of Intensive Care Units Mechanical Ventilators

“…A mechanical ventilator for intensive care units is an automatic machine designed to provide all or part of the work the body must perform to move gas into and out of the lungs [11]. Generally, it consists of two blocks:…”

“…The control system of the ICU ventilator allows the operators/doctors to set different ventilation modes according to the required parameters, such as, respiratory rate (RR), peak inspiratory flow rate (I pf ), the percentage of inhaled oxygen (FiO 2 ), inspiratory: expiratory ratio (I:E), tidal volume (V T ), peak of inspiratory pressure (PIP), and the positive end-expiratory pressure (PEEP) [9,10]. At least three of these parameters have to be set independently in order to achieve the required ventilation mode [11].…”

“…The energy needed to expand the patient's lungs can alternatively be supplied by compressed gas from the wall outlets of the hospital (general range 2.5-7 bar). The electric power system has the advantage of being able to be used wherever there is an electrical source; however, as the electric motor consists of bearings and connecting rods in motion, it becomes unreliable if used for a prolonged period of time [11]. The control and setting system is considered the ventilator's brain [5].…”

“…• An additional filter (10), used to protect the downstream inspiratory valve (11) and the patient against possible contaminating particles carried by the gas; • An inspiratory valve (11), which in the modern ventilator is a proportional valve, whose opening degree can be controlled accurately and that allows the system to obtain a precise control of the gas inhaled by the patient; in some models, such as the Galileo model [12], this valve is also equipped with a position sensor coupled with a differential pressure sensor measuring the pressure difference across the orifice of the inspiratory valve in order to calculate the flow of gas; • A pressure sensor ( 14), used to measure the pressure at this point of the circuit; •…”

“…The pressure in the tank is calculated according to the mass, the volume, and the temperature of the tank. This block is characterised by four ports: a sole inlet port (port A), two outlet ports (port B, connected to the downstream inspiratory valve (11), and port C, connected to the nebulizer), and the thermal conserving port associated with the thermal mass of the gas volume (port H);…”