Pulmonary Impedance Research Articles

The pulsatile component of left atrial pressure has little effect on pulmonary artery impedance estimation in normal rats.

Pulmonary artery impedance (PAZ) that measures the pulsatile properties of the vasculature provides diagnostic and prognostic information in patients with pulmonary vascular diseases. While downstream pressure [i.e., left atrial (LA) pressure] should be considered when calculating static properties of pulmonary vasculature, PAZ is commonly estimated without taking into account the pulsatile component of LA pressure. We examined whether PAZ can be estimated with reasonable accuracy without using LA pressure. Pulmonary artery (PA) flow, PA pressure, and LA pressure were measured under irregular pacing in eight normal Sprague‐Dawley rats. PAZ was estimated by analyzing a one‐input, one‐output system (I1O1 analysis) that does not include LA pressure, and a two‐input, one‐output system (I2O1 analysis) that includes LA pressure. Using a tube and 3‐element Windkessel model, PAZ was parameterized as peripheral resistance (RP), arterial compliance (CP), characteristic impedance (ZC), and transmission time to the reflection site (TD). These parameters were not significantly different between the I1O1 and I2O1 analyses (RP: 0.286 ± 0.040 vs. 0.274 ± 0.038 mmHg·min/mL, CP: 0.352 ± 0.049 vs. 0.343 ± 0.041 mL/mmHg, ZC: 0.115 ± 0.005 vs. 0.117 ± 0.005 mmHg·min/mL, TD: 13.2 ± 1.8 vs. 12.9 ± 1.7 msec). In conclusion, the I1O1 analysis that does not use LA pressure estimates PAZ with reasonable accuracy compared with the I2O1 analysis that uses LA pressure in normal rats. Our finding that the pulsatile component of LA pressure contributes little to PAZ estimation may justify the clinical use of the I1O1 analysis.

Pulmonary arterial input impedance reflects the mechanical properties of pulmonary arterial remodeling in rats with pulmonary hypertension

AimsAlthough pulmonary arterial remolding in pulmonary hypertension (PH) changes the mechanical properties of the pulmonary artery, most clinical studies have focused on static mechanical properties (resistance), and dynamic mechanical properties (compliance) have not attracted much attention. As arterial compliance plays a significant role in determining afterload of the right ventricle, we evaluated how PH changes the dynamic mechanical properties of the pulmonary artery using high-resolution, wideband input impedance (ZPA). We then examined how changes in ZPA account for arterial remodeling. Clarification of the relationship between arterial remodeling and ZPA could help evaluate arterial remodeling according to hemodynamics. Main methodsPH was induced in Sprague–Dawley rats with an injection of Sugen5416 (20 mg/kg) and 3-week exposure to hypoxia (10% oxygen) (SuHx). ZPA was evaluated from pulmonary artery pressure and flow under irregular pacing. Pulmonary histology was examined at baseline and 1, 3, and 8 weeks (n = 7, each) after Sugen5416 injection. Key findingsSuHx progressively increased pulmonary arterial pressure. ZPA findings indicated that SuHx progressively increased resistance (baseline: 9.3 ± 3.6, SuHx1W: 20.7 ± 7.9, SuHx3W: 48.8 ± 6.9, SuHx8W: 62.9 ± 17.8 mm Hg/mL/s, p < 0.01) and decreased compliance (baseline: 11.9 ± 2.1, SuHx1W: 5.3 ± 1.7, SuHx3W: 2.1 ± 0.7, SuHx8W: 1.9 ± 0.6 × 10−3 mL/mm Hg, p < 0.01). The time constant did not significantly change. The progressive reduction in compliance was closely associated with wall thickening of small pulmonary arteries. SignificanceThe finding that changes in resistance were reciprocally associated with those in compliance indicates that resistant and compliant vessels are anatomically inseparable. The analysis of ZPA might help evaluate arterial remodeling in PH according to hemodynamics.

Noninvasive determination of the pulmonary artery input impedance

A reliable noninvasive method for the estimation of pulmonary function in healthy and diseased subjects should be of great importance in the prognosis, diagnosis, and treatment of pulmonary hypertension. Here we propose such a method, which is based on the parameter identification of the five-element Windkessel model of pulmonary circulation. The method requires the following input variables: the heart rate, the stroke volume, the Doppler echocardiographic measurements of the tricuspid regurgitation and the pulmonary valve velocity profiles, and estimations of the right atrium and the pulmonary vein pressure. The stroke volume is calculated as a product of the left ventricle outflow tract area and the velocity-time integral measured at the same place. The model parameter identification procedure is based on minimization of the root mean square error between the pulmonary artery root pressure calculated from the aforementioned Doppler velocity profiles (from the Bernoulli equation applied during the ejection phase) and the pressure from the Windkessel model during the same period. The output from the model contains the calculated pulmonary artery input impedance (i.e. the model parameters: pulmonary vascular resistance, pulmonary artery proximal and distal compliances, inertance, and characteristic impedance) and the pulmonary artery pressure profile during the whole heart period. Our method is applied to a subject with pulmonary hypertension. The right heart Swan-Ganz catheterization has been performed in this subject. The results obtained by using this method show that the five-element Windkessel model reconstructs the main features of the pulmonary artery input impedance very well: its modulus shows the minimum where the phase angle changes its sign. The pulmonary vascular resistance, the systolic, diastolic and mean pulmonary artery pressures obtained from the method are in good agreement with the values obtained invasively from the catheterization. Sensitivity analysis shows that the mean pulmonary pressure is fairly insensitive to slight overestimation/ underestimation of all input parameters, except for the right atrium pressure. The absolute error in the mean pulmonary artery pressure is nearly the same as the error in the right atrium pressure. Since the proposed method offers a deeper insight into the pulmonary circulation than the catheterization itself because it provides the proximal and distal compliance, the inertance and the characteristic impedance, it seems that it can serve in clinical practice as a good substitute for catheterization.

Terapias intervencionistas en hipertensión pulmonar

Despite advances in drug therapy, pulmonary hypertension—particularly arterial hypertension (PAH)—remains a fatal disease. Untreatable right heart failure (RHF) from PAH eventually ensues and remains a significant cause of death in these patients. Lowering pulmonary input impedance with different PAH-specific drugs is the obvious therapeutic target in RHF due to chronically increased afterload. However, potential clinical gain can also be expected from attempts to unload the right heart and increase systemic output. Atrial septostomy, Potts anastomosis, and pulmonary artery denervation are interventional procedures serving this purpose. Percutaneous balloon pulmonary angioplasty, another interventional therapy, has re-emerged in the last few years as a clear alternative for the management of patients with distal, inoperable, chronic thromboembolic pulmonary hypertension. The current review discusses the physiological background, experimental evidence, and potential clinical and hemodynamic benefits of all these interventional therapies regarding their use in the setting of RHF due to severe pulmonary hypertension.

Computational Fluid Dynamics Modeling of the Human Pulmonary Arteries with Experimental Validation.

Pulmonary hypertension (PH) is a chronic progressive disease characterized by elevated pulmonary arterial pressure, caused by an increase in pulmonary arterial impedance. Computational fluid dynamics (CFD) can be used to identify metrics representative of the stage of PH disease. However, experimental validation of CFD models is often not pursued due to the geometric complexity of the model or uncertainties in the reproduction of the required flow conditions. The goal of this work is to validate experimentally a CFD model of a pulmonary artery phantom using a particle image velocimetry (PIV) technique. Rapid prototyping was used for the construction of the patient-specific pulmonary geometry, derived from chest computed tomography angiography images. CFD simulations were performed with the pulmonary model with a Reynolds number matching those of the experiments. Flow rates, the velocity field, and shear stress distributions obtained with the CFD simulations were compared to their counterparts from the PIV flow visualization experiments. Computationally predicted flow rates were within 1% of the experimental measurements for three of the four branches of the CFD model. The mean velocities in four transversal planes of study were within 5.9 to 13.1% of the experimental mean velocities. Shear stresses were qualitatively similar between the two methods with some discrepancies in the regions of high velocity gradients. The fluid flow differences between the CFD model and the PIV phantom are attributed to experimental inaccuracies and the relative compliance of the phantom. This comparative analysis yielded valuable information on the accuracy of CFD predicted hemodynamics in pulmonary circulation models.

Interventional Therapies in Pulmonary Hypertension

Despite advances in drug therapy, pulmonary hypertension—particularly arterial hypertension (PAH)—remains a fatal disease. Untreatable right heart failure (RHF) from PAH eventually ensues and remains a significant cause of death in these patients. Lowering pulmonary input impedance with different PAH-specific drugs is the obvious therapeutic target in RHF due to chronically increased afterload. However, potential clinical gain can also be expected from attempts to unload the right heart and increase systemic output. Atrial septostomy, Potts anastomosis, and pulmonary artery denervation are interventional procedures serving this purpose. Percutaneous balloon pulmonary angioplasty, another interventional therapy, has re-emerged in the last few years as a clear alternative for the management of patients with distal, inoperable, chronic thromboembolic pulmonary hypertension. The current review discusses the physiological background, experimental evidence, and potential clinical and hemodynamic benefits of all these interventional therapies regarding their use in the setting of RHF due to severe pulmonary hypertension.

Analysis of the levels of Th9 cells and cytokines in the peripheral blood of mice with bronchial asthma.

The purpose of the study was to detect the level of T-helper type 9 (Th9) cells and the cytokine interleukin-9 (IL-9) in peripheral blood of mice with bronchial asthma, and to explore the relationship between the expression of Th9 cells and the pathogenesis of asthma. Thirty female-specific pathogen-free (SPF) Bagg' albino (BALB)/c mice were selected and randomly divided into the control group (n=15) and the bronchial observation group (n=15). Mice in the bronchial observation group were treated with ovalbumin (OVA) for sensitization and induction of a mouse model of asthma. The airway reactivity of mice was measured by a mouse pulmonary function apparatus using the non-invasive pulmonary impedance method. The proportions of Th9 cells in peripheral blood of mice in the two groups were detected using flow cytometry. Digital polymerase chain reaction (dPCR), enzyme-linked immunosorbent assay (ELISA) and western blot analysis were applied to detect the levels of IL-9 messenger ribonucleic acid (mRNA) and proteins in peripheral blood and lung tissues of mice in the two groups, respectively. Compared with that in the control group, the expression level of Th9 cells in the peripheral blood of mice in the observation group was significantly elevated (P<0.05), the expression level of IL-9 proteins in the peripheral blood was significantly increased (P<0.05), and the levels of IL-9 mRNA and proteins in lung tissues were significantly increased (P<0.05). The results show that the levels of Th9 cells and their cytokine IL-9 in the peripheral blood of mice with bronchial asthma are significantly increased, suggesting that Th9 cells play important roles in the pathogenesis of asthma.

Air pollution and pulmonary health: Effects of short-term indoor air quality intervention with portable air purifier

Introduction: Chronic ambient air pollution exposure is known to adversely affect health outcomes. While it will take a long time to improve the outdoor air quality in China, using an indoor air purifier can produce immediate reductions in indoor air pollution. This study aims to investigate the impacts of overnight use of an indoor air purifier on cardiopulmonary health. Methods: Seventy-two healthy non-smoking students were recruited into a randomized, double-blind crossover study. Between November to December 2015, each subject received 2 overnight 13-19-hour interventions consisting of a True filtration and a Sham filtration (purifiers with or without a HEPA filter and an active carbon filter) with a 2-week washout period in-between. Cardiopulmonary health parameters were assessed through spirometry for lung function, impulse oscillometry (IOS) for airway resistance and elastance, Vicorder for arterial stiffness, and biomarkers of inflammation, oxidative stress, and hemostasis. Results: The median outdoor PM2.5 level during the study was 47 µg/m3 (Q1-Q3 range: 30.7 µg/m3, 70.0 µg/m3). A preliminary analysis was done using a mixed effect linear model with the subject as the random effect. Pulmonary health impacts of True and Sham filtrations were compared as reflected in the change of each biomarker from “before” to “after” intervention. Compared to Sham filtration, True filtration was shown to significantly lower pulmonary impedance (Z5) by 0.16 (P=0.048) and airway resistance R10 by 0.138 (P=0.043). No significant changes in other impulse oscillometry measurements (R5-R20, X5, Fres), exhaled nitric oxide, and spirometry parameters (including FEV1, FVC, FEV1/FVC, and PEF) were observed. Conclusion: Under a moderate level of ambient air pollution, overnight use of an air purifier significantly reduces pulmonary impedance and airway resistance at 10Hz. Further analysis of the targeted molecular biomarkers is underway.

Early recovery of tricuspid annular isovolumic acceleration after mitral valve surgery - an observational study.

Patients undergoing mitral valve surgery are at risk for right ventricular (RV) dysfunction resulting from increased left atrial pressure and increased pulmonary artery impedance. Measures of longitudinal measures of RV function, such as displacement, are commonly performed but have been shown to be depressed after cardiac surgery despite good patient recovery. The aim of this observational study was to assess the early perioperative time course of longitudinal transthoracic echocardiographic (TTE) markers of RV function in a patient population undergoing mitral valve surgery. Twenty patients undergoing mitral valve surgery were enrolled in this observational study. Right ventricular longitudinal measurements (tricuspid annular plane systolic excursion [TAPSE], strain, annular velocity [S'], and isovolumic acceleration [IVA]) were performed using TTE and colour Doppler imaging preoperatively (day 1) and postoperatively (days 2 and 6). Comparisons were made between the preoperative and postoperative measurements. Adequate echocardiographic imaging was obtained for all 20 patients. The TAPSE, strain, and S' measures remained depressed for up to one week (i.e., day 6) after surgery compared to preoperative values. The IVA was depressed on the first postoperative day (P > 0.001), but by day 6 it was no different from the preoperative value (P = 0.37). The median [interquartile range] time to discharge from hospital was 7 [6-9] days. Persistent, significant depression of longitudinal markers of RV function despite functional improvement (discharge from hospital) make it difficult to assess recovery during the early perioperative period. Isovolumic acceleration, a load-independent measure of contractility, might be a more reliable measure of early recovery in RV function in this patient population.

NOVEL NON-INVASIVE ASSESSMENT OF PULMONARY ARTERIAL IMPEDANCE USING CARDIAC MAGNETIC RESONANCE IMAGING

The ability to assess pulmonary artery impedance (PAI) non-invasively will help detect early pulmonary artery (PA) remodeling as it takes into account pulsatility of PA. We describe a novel surrogate of invasive PAI, velocity transfer function (VTF), measured on cardiac magnetic resonance (CMR) and

Ultrasound-Guided Parasternal Block Allows Optimal Pain Relief and Ventilation Improvement After a Sternal Fracture.

IntroductionSternal fractures are a painful condition which can result in pulmonary morbidity if not treated promptly. The management of isolated fractures has changed from hospital to home-based treatment, provided other major injuries have been excluded. Pain management is the mainstay of treatment. In this case report, we describe how a parasternal block under ultrasound guidance for sternal fracture provided better analgesia thereby improving ventilation.Case reportA 26-year-old man was admitted to the emergency department following a road traffic accident. His initial evaluation revealed a radio-cubital displaced fracture at the elbow level with severe tenderness over the sternum. Chest X-ray on admission did not reveal any abnormality. On preoperative checkup he was found to have altered chest mechanics with severe pain and tenderness over the sternum. Arterial blood gas (ABG) analysis showed respiratory acidosis. Pulmonary electrical impedance tomography showed hypoventilation of anterior portions of both lungs. An ultrasound examination of the sternum showed a fractured sternum with complete disjunction. An ultrasound-guided bilateral parasternal block was performed which resulted in efficient analgesia and thereby improved his ventilation as indicated by the improvement in ABG.ConclusionTimely and proper analgesia can reduce the pulmonary morbidity in sternal fractures. Of the various analgesic techniques, parasternal block under ultrasound guidance is a relatively simple, safe, and target-specific procedure that can provide efficient pain relief.Electronic supplementary materialThe online version of this article (doi:10.1007/s40122-016-0050-5) contains supplementary material, which is available to authorized users.

Development of a servo pump system for in vivo loading of pathological pulmonary artery impedance on the right ventricle of normal rats.

Pulmonary artery (PA) impedance provides detailed information on right ventricular (RV) afterload in pulmonary hypertension (PH). This study aimed to examine PA impedance in a rat model of monocrotaline-induced PH (MCT-PH) and to develop an experimental system for in vivo loading of pathological PA impedance on the RV of normal rats. PA impedance was quantified in normal (n= 10) and MCT-PH rats (n= 10) using a three-element Windkessel (3-WK) model. Compared with normal rats, MCT-PH rats had higher characteristic impedance (ZC) and peripheral pulmonary resistance (RP) (ZC: 0.121 ± 0.039 vs. 0.053 ± 0.017 mmHg·min·ml(-1), P< 0.001; RP: 0.581 ± 0.334 vs. 0.252 ± 0.105 mmHg·min·ml(-1), P= 0.013) and lower pulmonary artery compliance (CP) (0.242 ± 0.131 vs. 0.700 ± 0.186 ml/mmHg, P< 0.001). In another group of 10 normal rats, a computer-controlled servo pump was connected to the left PA for loading PA impedance with parameters in pathological ranges designed by the 3-WK model. Activation of the servo pump decreased the error of measured vs. target PA impedance (modulus: from 0.047 ± 0.020 without pump activation to 0.019 ± 0.007 with pump activation,P< 0.001; phase: 0.085 ± 0.028 to 0.043 ± 0.012 radians,P< 0.001). In conclusion, MCT-PH increases ZC and RP and decreases CP Our servo pump system, which is capable of imposing arbitrary PA impedance with pathological parameters, may offer a unique opportunity to delineate the pathological significance of PA impedance in PH.

A pulmonary artery loading system to impose pathological pulmonary artery impedance in rats

A pulmonary artery loading system to impose pathological pulmonary artery impedance in rats

Abstract 17109: Input Impedance Analysis of Pulmonary Hypertension Models Indicates That Monocrotaline and Sugen/hypoxia Induce Mechanically Different Vascular Remodeling

Introduction: Although complex pulmonary arterial remolding characterizes pulmonary hypertension (PH), the vascular mechanics has been evaluated by the static pressure-flow relationship (resistance, R) ignoring dynamic mechanical properties (compliance, C). We therefore evaluated pulmonary arterial input impedance (Z) capable of identifying not only resistance but also compliance in monocrotaline (MCT) and Sugen/Hypoxia (SuHx) PH models. Methods: In 6 weeks Sprague-Dawley rats, we induced PH by the subcutaneous injection of MCT (60 mg/kg) or Sugen5416 (20 mg/kg) with 3 weeks hypoxia. In anesthetized PH rats, we measured pulmonary artery flow (PAF) and pressure (PAP) at 1000 Hz for 107.52 seconds under irregular pacing. We Fourier transformed both PAF and PAP to derive ensembled power spectra and crosspower spectra and taking their ratio yielded Z. We fitted the 2-element Windkessel model to Z and estimated R and C. Results: MCT and SuHx significantly increased mean PAP (Control: 19.4±2.0, MCT: 31.3±4.0, SuHx: 39.4±6.5 mmHg, p &lt;0.01) and shifted Z upward indicating the increased R (Control: 17.8±3.3, MCT: 71.4±16.3, SuHx: 81.8±18.4 mmHg/ml/sec, p &lt;0.01). MCT and SuHx both decreased C (Control: 2.6±0.4, MCT: 1.5±0.6, SuHx: 0.9±0.2 х10 -3 ml/mmHg, p &lt;0.01). However, the time constant was higher in MCT than in SuHx (Control: 90.7±8.6, MCT: 130.0±21.5, SuHx: 92.6±2.0 msec, p &lt;0.05) (Figure). MCT predominantly remodeled resistance vessels while SuHx remodeled both resistance and compliance vessels. Conclusions: We conclude that the impedance analysis is capable of characterizing how remodeling affects vascular mechanical properties, which are not identifiable if we analyze resistance alone. Hence the impedance analysis is applicable in patients, it may serve as a new tool in functionally analyzing vascular remodeling in PH patients.

Pulmonary Impedance and Pulmonary Doppler Trace in the Perioperative Period.

Pulmonary hypertension and associated vascular changes may frequently accompany left-sided heart disease in the adult cardiac surgical population. Perioperative assessment of right ventricular function using echocardiography is well established. In general, understanding the constraints upon which the right ventricle must work is mostly limited to invasive monitoring consisting of pulmonary artery pressures, cardiac output, and pulmonary vascular resistance. The latter 2 measurements assume constant (mean) flows and pressures. The systolic and diastolic pressures offer a limited understanding of the pulsatile constraints, which may become significant in disease. In normal physiology, pressure and flow waves display near-similar contours. When left atrial pressure and pulmonary vascular resistance are increased, changes in pulmonary arterial compliance will result in elevated impedance to right ventricular ejection. Pressure reflections, the result of strong reflectors, return more quickly in a noncompliant system. They augment pulmonary artery pressure causing a premature reduction in flow. As a result, pressure and flow waves will now be dissimilar. The impact of vascular changes on right ventricular ejection can be assessed using pulmonary artery Doppler spectral imaging. The normal flow velocity profile is rounded at its peak. Earlier peaks and premature reductions in flow will make it appear more triangular. In some cases, the flow pattern may appear notched. The measurement of acceleration time, the time from onset to peak flow velocity is an indicator of constraint to ejection; shortened times have been associated with increased pulmonary vascular resistance and pressure. Understanding the changes in the pulmonary arterial system in disease and the physics of the hemodynamic alterations are essential in interpreting pulmonary artery Doppler data. Analyzing pulmonary artery Doppler flow signals may assist in the evaluation of right ventricular function in patients with pulmonary vascular disease.

Comparison of Non-invasive Methods – Impedance Cardiography and 2-dimentional Transthoracic Echocardiography Applied for Diagnostics of Pulmonary Artery Hypertension

By using an original policardiosignal analysis system developed in the Kaunas Institute of Cardiology, the method based on impedance cardiography for evaluation of blood pressure in pulmonary artery is presented. This method was tested by using data of 181 patients with various cardiac and pulmonary diseases, and for all of them two-dimentional transtoracic cardioechoscopy was performed in aim to confirm or exclude pulmonary artery hypertension Impedance cardiography is sensitive and specific method in diagnostics of pulmonary artery hypertension: the pulmonary artery hypertension was diagnosed by computed mean blood pressure in pulmonary with sensitivity of 72%, specificity – 90 %, and by systolic blood pressure in pulmonary artery – with sensitivity of 96 %, specificity – 90 %. The impedance cardiography is statistically trusted method and it strongly and significantly correlates with cardioechoscopy method when separating patients with or without pulmonary artery hypertension: the values of mean blood pressure obtained by impedance cardiogram and cardioechoscopy correlate in level of r = 0.755, p<0.001, and values of systolic blood pressure – in level of r = 0.893, p<0.001. These results permit to assume, that impedance cardiography, as non-invasive, inexpensive and user-friendliness method could be used for blood pressure evaluation in aim to detect the hypertension of pulmonary artery.

Feasibility Study of Pulsatile Left Ventricular Assist Device for Prolonged Ex Vivo Lung Perfusion

Exvivo lung perfusion (EVLP) has the potential to increase the donor pool for lung transplantation by facilitating resuscitation and extended evaluation of marginal organs. Current EVLP methodology employs continuous flow (CF) pumps that produce non-pulsatile EVLP hemodynamics. In this feasibility study, we tested the hypothesis that a pulsatile flow (PF) pump will provide better EVLP support than a CF pump through delivery of physiologic hemodynamics. Porcine lungs were supported in an EVLP model by centrifugal CF (n= 3) or PF (n= 4) left ventricular assist devices. Lungs were ventilated at 4 to 5 mL/kg, 0.21 fraction of inspired oxygen (FiO2), and perfused with an acellular, albumin-based solution corrected for osmolarity, acid-base balance, and carbon dioxide pressure (≤20 hours at 30°C) for a minimum of 12 hours support. Prostaglandin E1 and 30% albumin were infused continuously. Hemodynamic, respiratory, and blood gas parameters were continuously monitored and digitally recorded hourly. Parenchymal biopsies were used for quantification of wet to dry weight ratio. All lungs maintained function in the EVLP circuit for a minimum of 12 hours (mean 14.7 ± 1 hours) and demonstrated minimal edema formation. The PF EVLP produced higher pulsatility as demonstrated by greater energy equivalent pressure and surplus hemodynamic energy compared with CF EVLP (p < 0.05). There were no statistically significant differences in pulmonary impedance, arterial partial pressure of oxygen/fraction of inspired oxygen, wet to dry weight ratio, and peak airway pressure between CF and PF EVLP. The CF and PF EVLP systems successfully maintained lungs 12+ hours using a modified Steenperfusate (XVIVO Perfusion, Inc, Goteborg, Sweden); however, there were no statistically significantdifferences between CF and PF groups despite higher pulsatility, suggesting that PF may not offer immediate benefits over CF for prolonged exvivo lung preservation.

A servo-control system to impose desired pulmonary artery impedance in rats

A servo-control system to impose desired pulmonary artery impedance in rats

Measurement of the pulmonary input impedance for development of a sophisticated pulmonary vascular resistance model

Measurement of the pulmonary input impedance for development of a sophisticated pulmonary vascular resistance model

Determinants of right ventricular afterload (2013 Grover Conference series).

Right ventricular (RV) afterload consists of both resistive and capacitive (pulsatile) components. Total afterload can be measured directly with pulmonary artery input impedance spectra or estimated, either with lumped-parameter modeling or by pressure-volume analysis. However, the inverse, hyperbolic relationship between resistance and compliance in the lung would suggest that the pulsatile components are a predictable and constant proportion of the resistive load in most situations, meaning that total RV load can be estimated from mean resistive load alone. Exceptions include elevations in left atrial pressures and, to a lesser extent, chronic thromboembolic disease. The pulsatile components may also play a more significant role at normal or near-normal pulmonary artery pressures. Measures of coupling between RV afterload and RV contractility may provide important information not apparent by other clinical and hemodynamic measures. Future research should be aimed at development of noninvasive measures of coupling.