Distribution Of Pulmonary Blood Flow Research Articles

Intra-Amniotic Sildenafil and Rosiglitazone Late in Gestation Ameliorate the Pulmonary Hypertension Phenotype in Congenital Diaphragmatic Hernia

BackgroundPulmonary hypertension remains difficult to manage in congenital diaphragmatic hernia (CDH). Prenatal therapy may ameliorate postnatal pulmonary hypertension. We hypothesized that intra-amniotic (IA) injection of either sildenafil, a phosphodiesterase 5 inhibitor, or rosiglitazone, a PPAR-γ agonist, or both late in gestation would decrease the detrimental pulmonary vascular remodeling seen in CDH and improve peripheral pulmonary blood flow. MethodsPregnant rats were gavaged with nitrogen on embryonic day (E) 9.5 to induce fetal CDH. Sildenafil and/or rosiglitazone were administered to each fetus via an intra-amniotic injection after laparotomy on the pregnant dam at E19.5, and fetuses delivered at E21.5. Efficacy measures were gross necropsy, histology, peripheral blood flow assessment using intra-cardiac injection of a vascular tracer after delivery, and protein expression analysis. ResultsIntra-amniotic injections did not affect fetal survival, the incidence of CDH, or lung weight-to-body weight ratio in CDH fetuses. IA sildenafil injection decreased pulmonary vascular muscularization, and rosiglitazone produced an increase in peripheral pulmonary blood flow distribution. The combination of sildenafil and rosiglitazone decreased pulmonary artery smooth muscle cell proliferation. These intra-amniotic treatments did not show any negative effects in either CDH fetuses or control fetuses. ConclusionIA injection of sildenafil and rosiglitazone late in gestation ameliorates the pulmonary hypertensive phenotype of CDH and may have utility in clinical translation. Level of EvidenceNot applicable.

Calculating Relative Lung Perfusion Using Fluoroscopic Sequences and Image Analysis: The Fluoroscopic Flow Calculator.

Maldistribution of pulmonary blood flow in patients with congenital heart disease impacts exertional performance and pulmonary artery growth. Currently, measurement of relative pulmonary perfusion can only be performed outside the catheterization laboratory. We sought to develop a tool for measuring relative lung perfusion using readily available fluoroscopy sequences. A retrospective cohort study was conducted on patients with conotruncal anomalies who underwent lung perfusion scans and subsequent cardiac catheterizations between 2011 and 2022. Inclusion criteria were nonselective angiogram of pulmonary vasculature, oblique angulation ≤20°, and an adequate view of both lung fields. A method was developed and implemented in 3D Slicer's SlicerHeart extension to calculate the amount of contrast that entered each lung field from the start of contrast injection and until the onset of levophase. The predicted perfusion distribution was compared with the measured distribution of pulmonary blood flow and evaluated for correlation, accuracy, and bias. In total, 32% (79/249) of screened studies met the inclusion criteria. A strong correlation between the predicted flow split and the measured flow split was found (R2=0.83; P<0.001). The median absolute error was 6%, and 72% of predictions were within 10% of the true value. Bias was not systematically worse at either extreme of the flow distribution. The prediction was found to be more accurate for either smaller and younger patients (age 0-2 years), for right ventricle injections, or when less cranial angulations were used (≤20°). In these cases (n=40), the prediction achieved R2=0.87, median absolute error of 5.5%, and 78% of predictions were within 10% of the true flow. The current study demonstrates the feasibility of a novel method for measuring relative lung perfusion using conventional angiograms. Real-time measurement of lung perfusion at the catheterization laboratory has the potential to reduce unnecessary testing, associated costs, and radiation exposure. Further optimization and validation is warranted.

Pulmonary artery wave reflection and right ventricular function after lung resection

BackgroundLung resection has been shown to impair right ventricular function. Although conventional measures of afterload do not change, surgical ligation of a pulmonary artery branch, as occurs during lobectomy, can create a unilateral proximal reflection site, increasing wave reflection (pulsatile component of afterload) and diverting blood flow through the contralateral pulmonary artery. We present a cardiovascular magnetic resonance imaging (MRI) observational cohort study of changes in wave reflection and right ventricular function after lung resection. MethodsTwenty-seven patients scheduled for open lobectomy for suspected lung cancer underwent cardiovascular MRI preoperatively, on postoperative Day 2, and at 2 months. Wave reflection was assessed in the left and right pulmonary arteries (operative and non-operative, as appropriate) by wave intensity analysis and calculation of wave reflection index. Pulmonary artery blood flow distribution was calculated as percentage of total blood flow travelling in the non-operative pulmonary artery. Right ventricular function was assessed by ejection fraction and strain analysis. ResultsOperative pulmonary artery wave reflection increased from 4.3 (2.1–8.8) % preoperatively to 9.5 (4.9–14.9) % on postoperative Day 2 and 8.0 (2.3–11.7) % at 2 months (P<0.001) with an associated redistribution of blood flow towards the nonoperative pulmonary artery (r>0.523; P<0.010). On postoperative Day 2, impaired right ventricular ejection fraction was associated with increased operative pulmonary artery wave reflection (r=–0.480; P=0.028) and pulmonary artery blood flow redistribution (r=–0.545; P=0.011). At 2 months, impaired right ventricular ejection fraction and right ventricular strain were associated with pulmonary artery blood flow redistribution (r=–0.634, P=0.002; r=0.540, P=0.017). ConclusionsPulsatile afterload increased after lung resection. The unilateral increase in operative pulmonary artery wave reflection resulted in redistribution of blood flow through the nonoperative pulmonary artery and was associated with right ventricular dysfunction. Clinical trial registrationNCT01892800.

Automated analysis method to assess pulmonary blood flow distribution using conventional X-ray angiography

Quantitative assessment of the right-to-left ratio of pulmonary blood flow distribution is important for determining the clinical indications for treating pulmonary arterial branch stenosis. A novel theory was recently proposed that can be used to quantitatively assess the right-to-left ratio on conventional X-ray angiography images. In the proposal, further developments were indicated, especially automated calculation. In this study, a new automated algorithm was developed. In the X-ray image, regions of interest were set in right and left lung, and time-signal intensity curves were measured. The new automated algorithm is applied to determine the optimal time window for the analysis of the time-signal intensity curve and to calculate the slope of the curve in the optimized time window. The right-to-left ratios in seven consecutive patients calculated by the new automated algorithm were compared to those calculated by lung perfusion scintigraphy. The ratios were in good agreement with linear regression with a slope of 1.27 and a Pearson correlation coefficient of 0.95. The processing time was less than 10 s, which is one-eighth of the manual processing time. The new automated algorithm is accurate, stable, and fast enough for clinical use in the real world.

Expert consensus on the diagnosis and treatment of severe and critical coronavirus disease 2019.

Expert consensus on the diagnosis and treatment of severe and critical coronavirus disease 2019.

Non-invasive MRI Derived Hemodynamic Simulation to Predict Successful vs. Unsuccessful Catheter Interventions for Branch Pulmonary Artery Stenosis: Proof-of-Concept and Experimental Validation in Swine.

This study assessed the ability of hemodynamic simulations to predict the success of catheter interventions in a swine model of branch pulmonary artery stenosis (bPAS). bPAS commonly occurs in congenital heart disease and is often managed with catheter based interventions. However, despite technical success, bPAS interventions do not lead to improved distal pulmonary blood flow (PBF) distribution in approximately 1/3rd of patients. New tools are needed to better identify which patients with bPAS would most benefit from catheter interventions. For 13 catheter intervention cases in swine with surgically created left PAS (LPAS), PA pressures from right heart catheterization (RHC) and PBF distributions from MRI were measured before and after catheter interventions. Hemodynamic simulations with a reduced order computational fluid dynamics (CFD) model were performed using non-invasive PBF measurements derived from MRI, and then correlated with changes in invasive measures of hemodynamics and PBF distributions before and after catheter intervention to relieve bPAS. Compared to experimentally measured changes in left PBF distribution, simulations had a small bias (3.4 ± 11.1%), moderate agreement (ICC = 0.69 [0.24-0.90], 0.71 [0.23-0.91]), and good diagnostic capability to predict successful interventions (> 20% PBF increase) (AUC 0.83 [0.59-1.0]). Simulations had poorer prediction of changes in stenotic pressure gradient (ICC = 0.28 [- 0.33 to 0.73], r = 0.57 [- 0.04 to 0.87]) and MPA systolic pressure (ICC = 0.00 [- 0.52 to 0.53], r = 0.29 [- 0.32 to 0.72]). While there was only weak to moderate agreement between predicted and measured changes in PA pressures and pulmonary blood flow distributions, hemodynamic simulations did show good diagnostic value for predicting successful versus unsuccessful catheter based interventions to relieve bPAS. The results of this proof of concept study are promising and should encourage future development for using hemodynamic models in planning interventions for patients with bPAS.

Roles of Electrical Impedance Tomography in Determining a Lung Protective Strategy for Acute Respiratory Distress Syndrome in the Era of Coronavirus Disease 2019.

Electrical impedance tomography (EIT) is noninvasive and can be used at the bedside for real-time evaluation to identify ventilation distribution of infected lungs. This review briefly describes the basic principle of EIT and summarizes the latest findings on its potential contribution to lung protective strategies in coronavirus disease 2019 patients. Additionally, experimental approaches for detecting the distribution of pulmonary blood flow in coronavirus disease 2019 patients are presented. The findings underscore the role of EIT in determining lung protective strategies for coronavirus disease 2019-associated acute respiratory distress syndrome.

Awake prone positioning in COVID-19

In the absence of effective targeted therapies for COVID-19, optimisation of supportive care is essential. Lung injury with features of acute respiratory distress syndrome (ARDS) appears to be the principal...

Red Bull Increases Heart Rate at Near Sea Level and Pulmonary Shunt Fraction at High Altitude in a Porcine Model.

Red Bull energy drink is popular among athletes, students and drivers for stimulating effects or enhancing physical performance. In previous work, Red Bull has been shown to exert manifold cardiovascular effects at rest and during exercise. Red Bull with caffeine as the main ingredient increases blood pressure in resting individuals, probably due to an increased release of (nor)-epinephrine. Red Bull has been shown to alter heart rate or leaving it unchanged. Little is known about possible effects of caffeinated energy drinks on pulmonary ventilation/perfusion distribution at sea level or at altitude. Here, we hypothesized a possible alteration of pulmonary blood flow in ambient air and in hypoxia after Red Bull consumption. We subjected eight anesthetized piglets in normoxia (FiO2 = 0.21) and in hypoxia (FiO2 = 0.13), respectively, to 10 mL/kg Red Bull ingestion. Another eight animals served as controls receiving an equivalent amount of saline. In addition to cardiovascular data, ventilation/perfusion distribution of the lung was assessed by using the multiple inert gas elimination technique (MIGET). Heart rate increased in normoxic conditions but was not different from controls in acute short-term hypoxia after oral Red Bull ingestion in piglets. For the first time, we demonstrate an increased fraction of pulmonary shunt with unchanged distribution of pulmonary blood flow after Red Bull administration in acute short-term hypoxia. In summary, these findings do not oppose moderate consumption of caffeinated energy drinks even at altitude at rest and during exercise.

P2742Right ventricular stroke volume during dobutamine stress magnetic resonance compared to lung perfusion and peak oxygen uptake after arterial switch operation for transposition of the great arteries

Abstract Objectives Abnormal pulmonary perfusion due to stenosis of the central pulmonary arteries is common after neonatal arterial switch operation (ASO) for transposition of the great arteries (TGA). We conducted a monocentric prospective study in young adults after neonatal ASO for TGA to evaluate the effects of abnormal pulmonary perfusion on the increase of the right ventricular stroke volume (RVSV) during dobutamine stress magnetic resonance (DSMR) and on cardiopulmonary exercise capacity. Methods 68 unselected patients (age 18–29 years) underwent CMR at rest and under dobutamine stress (10 to 40 μg/kg/min). RVSV, pulmonary blood flow distribution (PBFD) and peak flow velocity were derived from phase contrast mapping in the main, right and left pulmonary artery (PA) at rest and each stress level. A cardiopulmonary exercise test (CPET) was performed at the same day. All patients reached maximal exercise effort according to heart rate and respiratory exchange rate. Results PBFD at rest: 9/68 patients (13%, ASO-S) had abnormal pulmonary perfusion at rest, defined as PBFD &gt;2:1 (right/left or left/right) and/or relevant stenosis of the main PA (Vmax &gt;2.5 m/s). 59/68 patients (87%, ASO-N) had normal pulmonary perfusion. PBFD under DSMR: (1) In the whole patient group, there was no increase of PBFD under stress compared to PBFD at rest. On an individual patient level, no relevant worsening of abnormal PBFD was found. (2) Under low dose dobutamine, ASO-S had a significantly lower RVSV-increase (RVSVstress/RVSVrest) compared to ASO-N (see figure). However, under high dose dobutamine, this effect was no longer significant (see figure). (3) The RVSV-increase under low and high dose dobutamine did not correlate with peak oxygen uptake during CPET, neither in the total group nor in the subgroups (see table). Peak oxygen uptake was not significantly different between ASO-N and ASO-S (p=0,72). RVSV-increase compared to CPET peak VO2% ASO-total ASO-S ASO-N RVSV-increase/peak VO2% RVSV-increase/peak VO2% RVSV-increase/peak VO2% low dose dobu high dose dobu low dose dobu high dose dobu low dose dobu high dose dobu Pearson correlation coefficient −0.02 −0.05 0.01 −0.22 −0.05 −0.04 p-value 0.90 0.71 0.98 0.56 0.71 0.78 Figure 1 Conclusion (1) Patients with relevant stenosis of main PA and/or abnormal peripheral blood flow distribution (ASO-S) exhibit a reduced RVSV-increase under low dose dobutamine compared to patients without stenosis (ASO-N). This effect was not present under high dose dobutamine stress. (2) These findings did not correlate with peak oxygen uptake during CPET, an objective parameter of cardiopulmonary exercise capacity. (3) Therefore, a conservative proceeding rather than surgery or catheter intervention should be considered, especially in asymptomatic adult patients. Acknowledgement/Funding Supported by Kinderherzen, Fördergemeinschaft Deutsche Kinderherzzentren e.V.

Assessment of the Reconstructed Pulmonary Circulation With Lung Perfusion Scintigraphy After Unifocalization and Repair of Tetralogy of Fallot With Major Aortopulmonary Collaterals.

Pulmonary vascular supply in tetralogy of Fallot (TOF) with major aortopulmonary collaterals (MAPCAs) is highly variable. Our approach to surgical management of this condition emphasizes early repair including unifocalization and reconstruction of the pulmonary circulation, incorporating all lung segments and addressing stenoses both proximal to and within the lung, in addition to ventricular septal defect closure. At our institution, we have over 15 years of experience using lung perfusion scintigraphy (LPS) to assess the distribution of pulmonary blood flow after complete unifocalization and repair. We reviewed clinical and quantitative LPS data in 310 patients who underwent complete unifocalization and repair of TOF/MAPCAs from 2003 to 2018 at our institution. Postrepair relative lung perfusion distributions were determined from LPS initially obtained at our institution within 60 days after repair and thereafter. Total lung perfusion to the right and left lungs was 58.0% ± 14.2% and 42.0% ± 14.2%, respectively. Perfusion was balanced in 75% of patients and unbalanced in 25%, including 11% in whom it was extremely unbalanced. On multivariable analysis, older age at repair, surgery other than a single-stage complete unifocalization, and native anatomy consisting of unilateral pulmonary blood supply through a ductus arteriosus were associated with unbalanced perfusion. We present our experience using LPS as an outcome measure after surgical repair of TOF/MAPCAs. Balanced lung perfusion was present in the majority of patients who had complete repair of TOF/MAPCAs performed at our center.

Supine, prone, right and left gravitational effects on human pulmonary circulation

BackgroundBody position can be optimized for pulmonary ventilation/perfusion matching during surgery and intensive care. However, positional effects upon distribution of pulmonary blood flow and vascular distensibility measured as the pulmonary blood volume variation have not been quantitatively characterized. In order to explore the potential clinical utility of body position as a modulator of pulmonary hemodynamics, we aimed to characterize gravitational effects upon distribution of pulmonary blood flow, pulmonary vascular distension, and pulmonary vascular distensibility.MethodsHealthy subjects (n = 10) underwent phase contrast cardiovascular magnetic resonance (CMR) pulmonary artery and vein flow measurements in the supine, prone, and right/left lateral decubitus positions. For each lung, blood volume variation was calculated by subtracting venous from arterial flow per time frame.ResultsBody position did not change cardiac output (p = 0.84). There was no difference in blood flow between the superior and inferior pulmonary veins in the supine (p = 0.92) or prone body positions (p = 0.43). Compared to supine, pulmonary blood flow increased to the dependent lung in the lateral positions (16–33%, p = 0.002 for both). Venous but not arterial cross-sectional vessel area increased in both lungs when dependent compared to when non-dependent in the lateral positions (22–27%, p ≤ 0.01 for both). In contrast, compared to supine, distensibility increased in the non-dependent lung in the lateral positions (68–113%, p = 0.002 for both).ConclusionsCMR demonstrates that in the lateral position, there is a shift in blood flow distribution, and venous but not arterial blood volume, from the non-dependent to the dependent lung. The non-dependent lung has a sizable pulmonary vascular distensibility reserve, possibly related to left atrial pressure. These results support the physiological basis for positioning patients with unilateral pulmonary pathology with the “good lung down” in the context of intensive care. Future studies are warranted to evaluate the diagnostic potential of these physiological insights into pulmonary hemodynamics, particularly in the context of non-invasively characterizing pulmonary hypertension.

Repair of Ductus or Hemi-Truncus to One Lung and Major Aortopulmonary Collaterals to the Other Lung

There are patients born with pulmonary atresia and a ductus arteriosus or hemi-truncus to one lung and major aortopulmonary collateral arteries (MAPCAs) to the contralateral lung. The purpose of this study was to review our surgical results for this relatively rare subset of patients. This was a retrospective review of 35 patients with ductus/hemi-truncus in association with pulmonary atresia with ventricular septal defect and MAPCAs. Our surgical algorithm is bifurcated into two strategies: (1)patients with "favorable" MAPCAs are candidates for single stage complete repair, and (2) patients with "unfavorable"MAPCAs undergo a staged approach. The median age at surgery was 3 months (range, 1 to 7 months), and the mean number of MAPCAs was 3.1 ± 1.3. Twenty patients underwent a single stage complete repair. All 20 of these patients are alive with a right ventricle to aortic pressure ratio of 0.34 ± 0.07. The distribution of pulmonary blood flow by lung perfusion scan was 44% to the right and 56% to the left lung. Fifteen patients underwent a staged approach, including unifocalization of the MAPCAs to a central shunt. There were 2 interim deaths. Twelve patients have undergone complete repair with a right ventricle to aortic pressure ratio of 0.38 ± 0.07. There was 1 late death after complete repair. The distribution of pulmonary blood flow was 39% to the right and 61% to the left lung. The data demonstrate that 32 of 35 patients with ductus/hemi-truncus and MAPCAs ultimately achieved complete repair with relatively low pulmonary artery pressures.

Experimental investigation of the effect of non-Newtonian behavior of blood flow in the Fontan circulation

The Fontan procedure for univentricular heart defects creates a unique circulation where all pulmonary blood flow is passively supplied directly from systemic veins. Computational simulations, aimed at optimizing the surgery, have assumed blood to be a Newtonian fluid without evaluating the potential error introduced by this assumption. We compared flow behavior between a non-Newtonian blood analog (0.04% xanthan gum) and a control Newtonian fluid (45% glycerol) in a simplified model of the Fontan circulation. Particle image velocimetry was used to examine flow behavior at two different cardiac outputs and two caval blood flow distributions. Pressure and flow rates were measured at each inlet and outlet. Velocity, shear strain, and shear stress maps were derived from velocity data. Power loss was calculated from pressure, flow, and velocity data. Power loss was increased in all test conditions with xanthan gum vs. glycerol (mean 10 ± 2.9% vs. 5.6 ± 1.3%, p=0.032). Pulmonary blood flow distribution differed in all conditions, more so at low cardiac output. Caval blood flow mixing patterns and shear stress were also qualitatively different between the solutions in all conditions. We conclude that assuming blood to be a Newtonian fluid introduces considerable error into simulations of the Fontan circulation, where low-shear flow predominates.

Quantitative pulmonary blood flow measurement using 15O-H2O PET with and without tissue fraction correction: a comparison study

BackgroundPhysiological measures per lung parenchyma, rather than per lung volume, sometimes reflect the disease status. PET images of the lung, which are usually expressed per lung volume, could confound the interpretation of the disease status, especially in cases with a prominent heterogeneity in aeration. The aim of the present study was to develop a method for measuring pulmonary blood flow (PBF) with aeration correction using 15O-H2O PET and to compare the results with those obtained using a conventional method. We obtained the voxel-based tissue fraction (TF) derived from density images converted from transmission images obtained using an external 137Cs point source. Quantitative PBF values with and without the TF were calculated using 15O-H2O PET to examine contralateral lung tissue in 9 patients with unilateral lung cancer. The heterogeneity in PBF before and after TF correction was then evaluated and compared. As a measure of PBF heterogeneity, we used the skewness and kurtosis of the PBF distribution.ResultsThe mean PBF of contralateral lung was 1.4 ± 0.3 mL/min per mL of lung. The TF-corrected PBF was 5.0 ± 0.6 mL/min per mL of lung parenchyma. After TF correction, the skewness and kurtosis of the PBF decreased significantly.ConclusionsThe present PBF calculation method using TF correction demonstrated that the normal PBF increased significantly and the PBF distribution became uniform. The proposed TF correction method is a promising technique to account for variations in density when interpreting PBF in PET studies.

Assessment of Transcapillary Water Exchange in the Lungs by Active Radiometry

The possibility of noninvasive assessment of transcapillary water exchange in the lungs using stimulated microwave emission of the chest organs is discussed. The results of the study showed that the distribution of 1 GHz microwave emission of tissues probed using low-intensity electromagnetic waves at 65 GHz corresponded to the distribution of pulmonary blood flow. Calculations showed that the intensity of transcapillary water exchange in the lungs was distributed exponentially from the apices to the basal parts of the lungs. The distribution of the transcapillary water exchange was shown to vary according to the pulmonary perfusion gradient, which is indicative of a correlation between the parameters of pulmonary perfusion and the intensity of stimulated microwave emission of tissues at the frequency of 1 GHz. This correlation can be used for noninvasive assessment of pulmonary perfusion by active radiometry.

The effect of lung deformation on the spatial distribution of pulmonary blood flow.

Pulmonary perfusion measurement using magnetic resonance imaging combined with deformable image registration enabled us to quantify the change in the spatial distribution of pulmonary perfusion at different lung volumes. The current study elucidated the effects of tidal volume lung inflation [functional residual capacity (FRC)+500ml and FRC+1litre] on the change in pulmonary perfusion distribution. Changes in hydrostatic pressure distribution as well as transmural pressure distribution due to the change in lung height with tidal volume inflation are probably bigger contributors to the redistribution of pulmonary perfusion than the changes in pulmonary vasculature resistance caused by lung tissue stretch. Tidal volume lung inflation results in structural changes in the pulmonary circulation, potentially affecting pulmonary perfusion. We hypothesized that perfusion is recruited to regions receiving the greatest deformation from a tidal breath, thus ensuring ventilation-perfusion matching. Density-normalized perfusion (DNP) magnetic resonance imaging data were obtained in healthy subjects (n=7) in the right lung at functional residual capacity (FRC), FRC+500ml, and FRC+1.0l. Using deformable image registration, the displacement of a sagittal lung slice acquired at FRC to the larger volumes was calculated. Registered DNP images were normalized by the mean to estimate perfusion redistribution (nDNP). Data were evaluated across gravitational regions (dependent, middle, non-dependent) and by lobes (upper, RUL; middle, RML; lower, RLL). Lung inflation did not alter mean DNP within the slice (P=0.10). The greatest expansion was seen in the dependent region (P<0.0001: dependent vs non-dependent, P<0.0001: dependent vs middle) and RLL (P=0.0015: RLL vs RUL, P<0.0001: RLL vs RML). Neither nDNP recruitment to RLL [+500ml=-0.047(0.145), +1litre=0.018(0.096)] nor to dependent lung [+500ml=-0.058(0.126), +1litre=-0.023(0.106)] were found. Instead, redistribution was seen in decreased nDNP in the non-dependent [+500ml=-0.075(0.152), +1litre=-0.137(0.167)) and increased nDNP in the gravitational middle lung [+500ml=0.098(0.058), +1litre=0.093(0.081)] (P=0.01). However, there was no significant lobar redistribution (P<0.89). Contrary to our hypothesis, based on the comparison between gravitational and lobar perfusion data, perfusion was not redistributed to the regions of the most inflation. This suggests that either changes in hydrostatic pressure or transmural pressure distribution in the gravitational direction are implicated in the redistribution of perfusion away from the non-dependent lung.

Main pulmonary artery area limits exercise capacity in patients long-term after arterial switch operation

ObjectivesDespite excellent survival in patients after the arterial switch operation, reintervention is frequently required and exercise capacity is decreased in a substantial number of patients. This study relates right-sided imaging features in patients long-term after the arterial switch operation to exercise capacity and ventilatory efficiency to investigate which lesions are functionally important. MethodsPatients operated in the UMC Utrecht, the Netherlands (1976-2001) and healthy controls underwent cardiac magnetic resonance imaging and cardiopulmonary exercise testing within 1 week. We measured main, left, and right pulmonary artery cross-sectional areas, pulmonary blood flow distribution, peak oxygen uptake, and minute ventilation relative to carbon dioxide elimination. ResultsA total of 71 patients (median age, 20 [12-35] years, 73% were male) and 21 healthy controls (median age, 26 [21-35] years, 48% were male) were included. Main, left, and right pulmonary artery areas were decreased compared with controls (190 vs 269 mm2/m2, 59 vs 157 mm2/m2, 98 vs 139 mm2/m2, respectively, all P < .001); however, pulmonary blood flow distribution was comparable (P = .722). Peak oxygen uptake and minute ventilation relative to carbon dioxide elimination were 88% ± 20% and 23.7 ± 3.8, respectively, with 42% and 1% of patients demonstrating abnormal results (≤84% and ≥34, respectively). The main pulmonary artery area significantly correlated with peak oxygen uptake (r = 0.401, P = .001) and pulmonary blood flow distribution with minute ventilation relative to carbon dioxide elimination (r = −0.329, P = .008). Subanalysis (<18, 18-25, >25 years) showed that the main pulmonary artery area was smaller in older age groups. In multivariable analysis, the main pulmonary artery area was independently associated with peak oxygen uptake (P = .032). ConclusionsIn adult patients after the arterial switch operation, narrowing of the main pulmonary artery is a common finding and is the main determinant of limitation in functional capacity, rather than pulmonary branch stenosis.

Effects of pulmonary acid aspiration on the regional pulmonary blood flow within the first hour after injury: An observational study in rats.

Gastric aspiration events are recognized as a major cause of pneumonitis and the development of acute respiratory distress syndrome. The first peak in the inflammatory response has been observed one hour after acid-induced lung injury in rats. The spatial pulmonary blood flow (PBF) distribution after an acid aspiration event within this time frame has not been adequately studied. We determined therefore PBF pattern within the first hour after acid aspiration. Anesthetized, spontaneous breathing rats (n = 8) underwent unilateral endobronchial hydrochlorid acid instillation so that the PBF distributions between the injured and non-injured lungs could be compared. The signal intensity of the lung parenchyma after injury was measured by magnetic resonance tomography. PBF distribution was determined by measuring the concentration of [68Ga]-radiolabeled microspheres using positron emission tomography. Following acid aspiration, magnetic resonance images revealed increased signal intensity in the injured regions accompanied by reduced oxygenation. PBF was increased in all injured lungs (171 [150; 196], median [25%; 75%]) compared to the blood flow in all uninjured lungs (141 [122; 159], P = 0.0078). From the first minute until fifty minutes after acid-induced acute lung injury, the PBF was consistently increased in the injured lung. These blood flow elevation was accompanied by significant hypoxemia.

Acute respiratory distress syndrome: we can't miss regional lung perfusion!

In adult respiratory distress syndrome (ARDS), life-threatening hypoxemia may occur, dictating the need for differentiated ventilator strategies. Pronounced consolidation and/or atelectasis have been well documented in ARDS, but the contribution of regional perfusion to oxygenation has been poorly addressed. Evidence has accumulated that, in ARDS, regional perfusion is extremely variable and may affect oxygenation, independently from the amount of atelectatic-consolidated lung regions. Thus, the response in oxygenation to different ventilatory settings, both during controlled and assisted mechanical ventilation, should be interpreted with caution. In fact, gas exchange may be not determined solely by changes in aeration, but also redistribution of perfusion. Furthermore, regional perfusion can play an important role in worsening of lung injury due to increased transmural pressures. In addition, distribution of perfusion in lungs might affect the delivery of drugs through the pulmonary circulation, including antibiotics. In recent years, several techniques have been developed to determine pulmonary blood flow with increasing level of spatial resolution, allowing a better understanding of normal physiology and various pathophysiological conditions, but most of them are restricted to experimental or clinical research. Lung ultrasound and novel algorithms for electrical impedance tomography represent new promising techniques that could enable physicians to assess the distribution of pulmonary blood flow at the bedside. In ARDS, we cannot afford missing regional lung perfusion!Please see related article: http://dx.doi.org/10.1186/s12871-015-0013-0.