Study of Ventricular Interdependence in Hemodialysis Patients

Background and objectivesStudy of respiratory variations in mitral valve (MV) Doppler flow in hemodialysis (HD) patients has not been investigated and normal adult referenced echocardiographic value is used as an echocardiographic reference to HD patients who have unique hemodynamic. This work aimed to study the respiratory variation in MV Doppler flow in HD patients to determine if it has a unique pattern in these patients, and to study any relation between this variation and volume-related parameters.MethodsWe conducted a prospective cohort study, carried out on 118 patients who underwent regular HD. A standard echocardiography was performed on the patients before and within 6 hs after dialysis. During quiet breathing, the transmitral spectral Doppler E wave was measured during inspiratory and expiratory phases using plethysmography breath-cycle chest-adhesive electrodes. The mathematic differences and the percent changes (ventricular interdependent; VI) in E wave were calculated pre-and post-dialysis. Post dialysis difference in the percent changes (∆ E wave % changes) was calculated as follows: pre-dialysis percent changes of E wave – post dialysis percent changes of E wave/pre dialysis percent changes E wave x 100. ResultsThe means of the mathematic differences between the MV inspiratory and expiratory E pre-and post-dialysis were 0.07 ± 0.18 m/s and 0.08 ± 0.22 m/s respectively with an insignificant difference between both phases; p = 0.337. Meanwhile, the means of the percent variation in the MV inspiratory and expiratory E pre-and post-dialysis were 56 ± 7 % and 44 ± 1.1 % respectively, with a significant reduction after dialysis; P = 0.000. Spearman correlation showed a significant positive correlation between post- dialysis ∆ E wave % change and post-dialysis % change of weight (r = 0.318; P = 0.000). Moreover, post- dialysis % change of weight and post- dialysis % changes of most other volume-related variable were independent predictors of post- dialysis ∆ E wave % in HD patients. ConclusionThe pre- and post- dialysis respiratory changes in the MV E wave in HD patients were higher than the normal adult referenced values. This marked variation could be explained by the unique overloading condition and could explain the LV diastolic dysfunction and the unexplained pulmonary hypertension in HD patients.

Computational fluid dynamic models as tools to predict aerosol distribution in tracheobronchial airways

Aerosol and pollutants, in form of particulates 5–8 μm in main size face every day our respiratory system as natural suspension in air or forced to be inhaled as a coadjutant in a medical therapy for respiratory diseases. This inhalation happens in children to elderly, women and men, healthy or sick and disable people. In this paper we analyzed the inhalation of aerosol in conditions assimilable to the thermal therapy. We use a computational fluid dynamic 3D model to compute and visualize the trajectories of aerosol (3–7–10–25 µm) down to the sixth generation of bronchi, in a steady and dynamic condition (7 µm) set as breath cycle at rest. Results, compared to a set of milestone experimental studies published in literature, allow the comprehension of particles behavior during the inhalation from mouth to bronchi sixth generation, the visualization of jet at larynx constriction and vortices, in an averaged characteristic rigorous geometrical model including tracheal rings. Results on trajectories and deposition show the importance of the including transient physiological breath cycle on aerosol deposition analyses. Numerical and graphical results, may enable the design of medical devices and protocols to make the inhalations more effective in all the users’ population.

Computational Fluid Dynamic Models as Tools to Predict Aerosol Distribution in Tracheobronchial Airways

Background: Aerosol and pollutants, in form of particulates 5 – 8 um in main size face every day our respiratory system as natural suspension in air or forced to be inhaled as a coadjutant in a medical therapy for respiratory diseases. This inhalation happens in children to elderly, women and men, healthy or sick and disable people. In this paper we analyzed the inhalation of aerosol in conditions assimilable to the thermal therapy, in a model of patient representing an adult man. Results: We use a computational fluid dynamic 3D model to compute and visualize the trajectories of aerosol (3-7-10-25 µm) down to the sixth generation of bronchi, in a steady and dynamic condition (7 µm) set as breath cycle at rest. Results, compared to a set of milestones experimental studies published in literature, allow the comprehension of particles behavior during the inhalation from mouth to bronchi sixth generation, the visualization of jet at larynx constriction and vortices, in a characteristic geometrical model including tracheal rings. Conclusions: Results on trajectories and deposition show the importance of the including transient physiological breath cycle on aerosol deposition analyses. Furthermore results indicate that vorticity in the glottides and trachea sections mix the trajectories on the transversal plane, excluding meaningful relation between position of the inhalation across the mouth and the deposition lobe. Numerical and graphical results, usable from researchers, technicians and medical doctors, may enable the design of medical devices and protocols to make the inhalations more effective in all the users’ population.

A Novel System for Patient Ventilation and Dosing of Hyperpolarized 3He for Magnetic Resonance Imaging of Human Lungs

A versatile ventilator for controlling a patient’s breath cycle and dosing 3He gas has been designed and constructed. It is compatible with a medical magnetic resonance imaging scanner and can be incorporated into routine human lungs imaging procedure that employs hyperpolarized noble gas as a contrast agent. The system adapts to the patient’s lung volume and their breath cycle rhythm, providing maximum achievable comfort during the medical examination. Good quality magnetic resonance lung images of healthy volunteers were obtained. The system has the capability of recycling the exhaled gas to recover the expensive 3He isotope, and can be also adapted to human lung imaging with hyperpolarized 129Xe.

An Experimental Setup for API Assessment of a Valved Holding Chamber Device

Typically for young children and elders, the asthma treatment procedure using pMDI devices bring some usage coordination difficulties. Therefore, and accordingly to several asthma treatment guidelines, the prescription of a VHC, as an add-on device for the pMDI, is advisable. These devices consist of an expansion chamber where the air slows down, as well as, the pMDI spray plume. Allowing the patient to breathe whenever he wants, independently from the moment of the pMDI actuation, also reduces the “cold-freon” effect and allows a more effective evaporation of the propellant. The effectiveness evaluation of VHC and pMDI devices is made through the quantification of drug delivered to the patient lungs. A simple collection filter is not enough for an accurate assessment of the device. Since the size of the particles delivered matter the most, the use of an impaction apparatus is essential. Accordingly to the Canadian normative for VHC assessment (CAN/CSA/Z264.1-02:2008), the experimental testing shall be done by using a breath simulator instead of a constant flow pump. The evolution of these tests shall move towards more realistic testing conditions. This work reports the project and construction an experimental setup for a correct assessment of the VHC devices effectiveness. The experimental setup is based in the work of Foss & Keppel (1999) and the contribution of Finlay (1998) and Miller (2002). The project and optimization of the major components, such as, breath cycle simulator by means of a cam-follower mechanism, a mixing cone and the vacuum pump used, are herein described and discussed.

Numerical Analysis on the Influence of the Unsteady Effect upon the Flow Characteristics in a Human Airway

The focus is on the unsteady effect on the flow characteristics considering the real respiration in a human airway. In order to capture the unsteady effect, the flow characteristics were investigated and compared with that of steady flow by using the computational fluid dynamics technique. The real respiratory flow rate in a light workload was appliedto the inlet of airway. The unsteady effects especially appear when the flow rate accelerates in the inspiratory and the expiratory phase than other times in a breath cycle. The size of the flow recirculation zone, the turbulence fluctuation and the secondary flow intensity decrease because the unsteady effect reduces the strength of jets passing through the constriction of airway by interfering with the flow. These results imply that the unsteady effect should be considered to investigate the flow characteristics and the particle movement in a human airway.

Numerical Investigation of the Flow Characteristics Considering the Human Workloads in a Human Airway

The flow characteristicscan be sensitively changed by the respiration flow rate due to the complex geometries, e.g., bends, constrictions in a human airway. Also, caused by the switching the flow direction, the disturbance destabilizes the flow when a human breathes. Thus, the real breathing conditions, e.g., peak flow rate and the breath cycle time related to workload, should be considered to investigate on the flow characteristics in a human airway. In this study, realated to the human workloads, the effect of the change of the respiratory flow rate on the flow characteristics is investigated with the numerical method at the 4-specific normalized times in a breath cycle. In almost time of a breath cycle, as the workload increases, the flow recirculation zone decreases slightly because the energy transport toward the wall increases due to the turbulence fluctuation and the secondary motion.However, when the flow acclecrates in the expiratory phase, the flow recirculation zone increases because of the unsteady effect and the glottal jet. Thus, respiratory flow rate considering the human workloads and the unsteady effect caused by the real respiration should be considered to investigate the flow characteristics and the particle movement in a human airway.

Influence of dynamic and static physical activity features on respiratory system of junior schoolgirls

Aim. To study the influence of different types of physical exercise on components of gases convective transport in junior schoolgirls. Methods. Twenty two 9 year old schoolgirls were included. The functional condition of respiratory system was estimated based on pulmonary function tests and respiratory volumes. Isometric physical exercise test was performed by the left hand compression of a dynamometer with the effort equal of 50% from maximum possible effort within 1 minute. Dynamic physical load was dosed as 1,0 W per 1 kg of body weight while pedalling a stationary exercise bicycle ergometer. Statistical difference between groups was determined using Student’s t-statistics. Results. Influence of dynamic and static physical exercise on respiratory function tests in 9 year old schoolgirls was studied at the beginning, in the middle and at the end of the school year. The comparative analysis of respiratory function tests in 9 year old schoolgirls at the beginning of academic year showed that isometric physical exercise caused the breath rate increase, and dynamic physical exercise led to decrease of this parameter. At the same time both types of physical exercise caused decrease in expiratory time to total breath cycle time ratio. In the middle of the academic year isometric physical exercise caused the breath rate decrease and maximum voluntary ventilation increase. As a whole, both in the middle and at the end of the academic year the respiratory system of 9 year old schoolgirls reacted adequately in reply to different types of physical exercise to optimize the performance. Conclusion. The most unfavorable reaction of respiratory system in 9 year old schoolgirls in reply to static and dynamic physical exercise at the beginning of the academic year was registered as a decrease of expiratory time to total breath cycle time ratio. The optimal reaction of respiratory system in 9 year old schoolgirls in reply to dynamic physical exercise was registered both in the middle and at the end of the school year, to static physical exercise - at the end of the school year.