Slow Inflation Research Articles

Transcatheter Aortic Valve Implantation Using the Slow Balloon Inflation Technique: Making Balloon-Expandable Valves Partially Repositionable

In transcatheter aortic valve implantation procedures using balloon-expandable valves, the valve is deployed by rapid balloon inflation within a short period of rapid ventricular pacing. This system and deployment technique is generally considered to be nonrepositionable. We illustrate with two cases (transapical and transfemoral) the possibility to partially reposition the valve during its deployment if a slow balloon inflation technique were employed-a technique that may minimize the risk of valve mal-positioning and its attendant complications.

Atherotome Dislodgement and Successful Retrieval During Cutting Balloon Pulmonary Angioplasty

Cutting balloons (CBs) are beneficial for dilation of resistant branch pulmonary artery (PA) stenosis in children.1 There are rare reports of atherotome fracture2 and a Food and Drug Administration adverse event report of a fractured atherotome dislodging and remaining in the patient.3 We report CB atherotome dislodgement and embolization with successful retrieval in a patient with Alagille syndrome and branch PA stenosis. A 7-year-old girl with Alagille syndrome, systemic hypertension, branch PA stenosis, and a small patent ductus arteriosus was referred for left PA dilation and percutaneous patent ductus arteriosus closure to optimize her cardiac status before liver transplantation. Angiograms of the left PA demonstrated stenosis of the proximal left lower PA (LLPA) measuring 3.07 mm, with the distal LLPA measuring 6.2 mm. An 8-mm balloon (Sterling; Boston Scientific) was inflated to 8 atm with a 6-mm waist (Figure 1). Through a 7F long sheath (Check-Flo Performer Introducer, Mullins Design; …

Level-set-based reconstruction algorithm for EIT lung images: first clinical results

We show the first clinical results using the level-set-based reconstruction algorithm for electrical impedance tomography (EIT) data. The level-set-based reconstruction method (LSRM) allows the reconstruction of non-smooth interfaces between image regions, which are typically smoothed by traditional voxel-based reconstruction methods (VBRMs). We develop a time difference formulation of the LSRM for 2D images. The proposed reconstruction method is applied to reconstruct clinical EIT data of a slow flow inflation pressure–volume manoeuvre in lung-healthy and adult lung-injury patients. Images from the LSRM and the VBRM are compared. The results show comparable reconstructed images, but with an improved ability to reconstruct sharp conductivity changes in the distribution of lung ventilation using the LSRM.

Recurrent inflation and collapse in horizontally shaken granular materials

We report a striking effect observed experimentally in several granular materials when shaken horizontally: The material displays a recurrent alternation between a slow inflation phase, characterized by an increase in its volume, and a fast collapse phase, when the volume abruptly returns to its original value. The frequency of such phase alternations is totally decoupled from the frequency of the external drive. We argue that the inflation and collapse alternation arises from an interplay between the mechanical stability of the material and Reynolds dilatancy due to convective motion.

Functional and morphological assessment of early impairment of airway function in a rat model of emphysema

The aim of this study was to evaluate airway structure-function relations in elastase-induced emphysema in rats. Sprague-Dawley rats were treated intratracheally with 50 IU porcine pancreatic elastase (PPE, n = 8) or saline (controls, n = 6). Six weeks later, lung volumes [functional residual capacity (FRC), residual volume (RV), and total lung capacity (TLC)] and low-frequency impedance parameters (Newtonian resistance, R(N); tissue damping; tissue elastance, H) were measured, and tracheal sounds were recorded during slow inflation to TLC following in vivo degassing. The lungs were fixed and stained for standard morphometry, elastin, and collagen. In the PPE group, FRC and RV were higher [4.53 ± 0.7 (SD) vs. 3.28 ± 0.45 ml; P = 0.003 and 1.06 ± 0.35 vs. 0.69 ± 0.18 ml; P = 0.036, respectively], and H was smaller in the PPE-treated rats than in the controls (1,344 ± 216 vs. 2,178 ± 305 cmH(2)O/l; P < 0.001), whereas there was no difference in R(N). The average number of crackles per inflation was similar in the two groups; however, the crackle size distributions were different and the lower knee of the pressure-volume curves was higher in the PPE group. Microscopic images revealed different alveolar size distributions but similar bronchial diameters in the two groups. The treatment caused a slight but significant decrease in the numbers of alveolar attachments, no difference in elastin and slightly increased mean level and heterogeneity of collagen in the bronchial walls. These results suggest that tissue destruction did not affect the conventionally assessed airway resistance in this emphysema model, whereas the alterations in the recruitment dynamics can be an early manifestation of impaired airway function.

Tidal recruitment assessed by electrical impedance tomography and computed tomography in a porcine model of lung injury*

To determine the validity of electrical impedance tomography to detect and quantify the amount of tidal recruitment caused by different positive end-expiratory pressure levels in a porcine acute lung injury model. Randomized, controlled, prospective experimental study. Academic research laboratory. Twelve anesthetized and mechanically ventilated pigs. Acute lung injury was induced by central venous oleic acid injection and abdominal hypertension in seven animals. Five healthy pigs served as control group. Animals were ventilated with positive end-expiratory pressure of 0, 5, 10, 15, 20, and 25 cm H2O, respectively, in a randomized order. At any positive end-expiratory pressure level, electrical impedance tomography was obtained during a slow inflation of 12 mL/kg of body weight. Regional-ventilation-delay indices quantifying the time until a lung region reaches a certain amount of impedance change were calculated for lung quadrants and for every single electrical impedance tomography pixel, respectively. Pixel-wise calculated regional-ventilation-delay indices were plotted in a color-coded regional-ventilation-delay map. Regional-ventilation-delay inhomogeneity that quantifies heterogeneity of ventilation time courses was evaluated by calculating the scatter of all pixel-wise calculated regional-ventilation-delay indices. End-expiratory and end-inspiratory computed tomography scans were performed at each positive end-expiratory pressure level to quantify tidal recruitment of the lung. Tidal recruitment showed a moderate inter-individual (r = .54; p < .05) and intra-individual linear correlation (r = .46 up to r = .73 and p < .05, respectively) with regional-ventilation-delay obtained from lung quadrants. Regional-ventilation-delay inhomogeneity was excellently correlated with tidal recruitment intra- (r = .90 up to r = .99 and p < .05, respectively) and inter-individually (r = .90; p < .001). Regional-ventilation-delay can be noninvasively measured by electrical impedance tomography during a slow inflation of 12 mL/kg of body weight and visualized using ventilation delay maps. Our experimental data suggest that the impedance tomography-based analysis of regional-ventilation-delay inhomogeneity provides a good estimate of the amount of tidal recruitment and may be useful to individualize ventilatory settings.

Ventilation homogeneity improves with growth early in life

Some studies have suggested that lung clearance index (LCI) is age-independent among healthy subjects early in life, which implies that ventilation distribution does not vary with growth. However, other studies of older children and adolescents suggest that ventilation becomes more homogenous with somatic growth. We describe a new technique to obtain multiple breath washout (MBWO) in sedated infants and toddlers using slow augmented inflation breaths that yields an assessment of LCI and the slope of phase III, which is another index of ventilation inhomogeneity. We evaluated whether ventilation becomes more homogenous with increasing age early in life, and whether infants with chronic lung disease of infancy (CLDI) have increased ventilation inhomogeneity relative to full-term controls (FT). FT (N = 28) and CLDI (N = 22) subjects between 3 and 28 months corrected-age were evaluated. LCI decreased with increasing age; however, there was no significant difference between the two groups (9.3 vs. 9.5; P = 0.56). Phase III slopes adjusted for expired volume (S(ND)) increased with increasing breath number during the washout and decreased with increasing age. There was no significant difference in S(ND) between full-term and CLDI subjects (211 vs. 218; P = 0.77). Our findings indicate that ventilation becomes more homogenous with lung growth and maturation early in life; however, there is no evidence that ventilation inhomogeneity is a significant component of the pulmonary pathophysiology of CLDI.

Impact of blood pressure cuff inflation rates on flow-mediated dilatation and contralateral arm response

Flow-mediated dilatation (FMD) is widely used as an index of nitric oxide-mediated vasodilator function, yet its methodology has not been well established. Previous research indicates that a rapid inflation of a blood pressure cuff evokes systemic vasoconstriction, as it was observed even on non-occluded contralateral arm. This would potentially contribute to the variability of FMD readings and complicate the emerging evidence that non-occluded contralateral arm fingertip temperature responses during the FMD procedure may be an indicator of the presence of coronary artery disease. To test the hypotheses that rapid inflation of a blood pressure cuff could reduce FMD values and influence contralateral vasodilatory states, 33 apparently healthy adults (18 males and 15 females, 29±6 years) were studied in two randomized FMD trials. The blood flow-occluding cuff was inflated rapidly (<1 s) in one trial or slowly over 10 s in the other trial. Arterial diameter, fingertip temperature and infrared thermography were obtained throughout each session. FMD values were not different between the rapid and slow cuff inflation trials (5.9±0.6 vs 5.9±0.4%). There were no differences in reactive hyperaemia (6.4±1.6 vs 6.2±1.7 AU), shear stress (80±20 vs 77±17 dyn cm(-2)) and fingertip temperature rebound (TR; 1.8±1.2 vs 1.9±1.0 °C) between the rapid and slow inflation. Changes in finger temperature on the contralateral (non-occluded) arm were positively associated with those on the occluded arm (r=0.26 to 0.61, P<0.05). We concluded that rates of inflating a blood pressure cuff do not affect FMD and TR response, and that neurovascular-induced vasodilatation of the contralateral arm was not observed regardless of cuff inflation rates.

Transapical Aortic Valve Implantation in 194 Patients: Problems, Complications, and Solutions

Transapical aortic valve implantation is a novel approach for high-risk patients with severe aortic stenosis. During our learning curve, we were faced with several problems, technical difficulties, and complications, and our strategy and procedural technique evolved accordingly. We report our experience during the learning curve for establishing this new method. Between April 2008 and January 2010, 194 patients (mean age, 80 ± 9 years; range, 36 to 99 years) were treated by transapical aortic valve implantation. The mean Society of Thoracic Surgeons score was 23.5% ± 19.4% (range, 2.7% to 89.5%; logistic EuroSCORE, 41% ± 20%; range, 6% to 97%). We have established institutional guidelines on how to act in particular situations, with regard to patient selection, procedural steps, and complications concerning the procedure that have evolved according to our own experience. Mandatory angiographic visualization of the aortic root during valve deployment was introduced, combined with slow and gradual inflation of the balloon with possible correction of the valve position and its definitive position higher than we had been taught. Technical success was 99.5% with one conversion to conventional surgery (annulus rupture). One intraprocedural obstruction of the left coronary ostium was successfully treated by emergency stent implantation. The 30-day mortality was 5.7% for the whole group (11 of 194 patients), 3.8% for all patients without cardiogenic shock (7 of 182 patients), and 33% for the patients with cardiogenic shock (4 of 12 patients). There were 2 (1%) new clinical neurologic events postoperatively. A combination of patient-related evaluation and several small but precise technical modifications of the original transapical aortic valve implantation techniques reduced the rate of complications and increased success during the learning curve.

Regional lung volume changes during high-frequency oscillatory ventilation*

To investigate regional lung volume changes occurring during an inflation-deflation maneuver using high-frequency oscillatory ventilation. Prospective animal trial. Animal research laboratory. Six Yorkshire swine. Electrical impedance tomography was used to quantify regional ventilation during high-frequency oscillatory ventilation. The electrical impedance tomography-derived center of ventilation was used to describe the distribution of regional ventilation, whereas spectral analysis was used to describe regional ventilation-induced impedance changes. Lung injury was induced using surfactant lavage. Animals were transitioned to high-frequency oscillatory ventilation and a slow inflation-deflation maneuver was performed by changing mean airway pressure by 5 cm H2O every 15 mins to a maximum mean airway pressure of 40 cm H2O. The induction of lung injury was associated with a significant shift of the center of ventilation toward nondependent areas and an increase in shunt fraction (p < .001). During the following inflation-deflation maneuver using high-frequency oscillatory ventilation, inflation was associated with a shift of the center of ventilation from nondependent to dependent areas. Center of ventilation was significantly correlated with the shunt fraction (p < .001). Analyzing different lung layers along the gravitational axis separately, nondependent lung areas showed significantly decreased regional ventilation-induced impedance changes at higher pressures, suggesting overdistension, whereas dependent lung areas showed increased impedance changes, suggesting recruitment. The reverse was observed during deflation (all p < .05). The center of ventilation during high-frequency oscillatory ventilation correlated with oxygenating efficiency as measured by the shunt fraction. Lung recruitment during high-frequency oscillatory ventilation produced a significant shift of regional ventilation toward dependent areas of the lung and led to overdistension of nondependent areas.

Percutaneous Coronary Sinus Catheter Placement Aided by 3-Dimensional Transesophageal Echocardiography

Percutaneous Coronary Sinus Catheter Placement Aided by 3-Dimensional Transesophageal Echocardiography

Intermittent Positive Airway Pressure to Manage Hypoxia during One-lung Anaesthesia

The effect of intermittent positive airway pressure to the non-ventilated lung was assessed in 10 patients who desaturated during one-lung ventilation. Once their saturation fell below 95% they were given a slow inflation of 2 l/min of oxygen into the non-ventilated lung for two seconds. This was repeated every 10 seconds for five minutes or until the saturation rose to 98%, whichever was sooner. The initial mean SpO2 was 89.3% +/- 4.2%. All 10 patients had an increase in saturation. The mean saturation following intermittent positive airway pressure was 96.5% +/- 1.6% (P < 0.0001). Similarly, the mean oxygen tension rose from 67.2 +/- 12.8 mmHg to 98.9 +/- 19.8 mmHg. Intermittent positive airway pressure should be considered for patients who desaturate while undergoing one-lung ventilation.

Cannabinoid CB 1 receptors are expressed in the mouse urinary bladder and their activation modulates afferent bladder activity

Pharmacological studies have indirectly shown the possible presence of cannabinoid receptors in the urinary bladder and their potential role in reducing bladder inflammatory pain. However, the localization of cannabinoid receptors in the urinary bladder remains unknown and there are no published data on the effects of cannabinoids on the sensory system of the bladder. The present study was performed to evaluate the expression of the cannabinoid CB 1 receptors in the mouse urinary bladder and to assess their co-localization with the purinergic P2X 3 receptor, a major player in the transduction of sensory events in the bladder. Also, the effect of intravesical administration of a cannabinoid agonist on the electrical activity of bladder afferent fibers was studied. The expression of mRNA coding for CB 1 receptor was assessed by reverse transcriptase–polymerase chain reaction (RT-PCR). Immunofluorescence experiments were performed to study CB 1 and P2X 3 protein expression in the bladder. The electrical activity of bladder afferent fibers was recorded using an ex vivo bladder-nerve preparation. Mechanical stimulation of the bladder was performed by a controlled slow inflation with an external pump. A bolus of a cannabinoid agonist (AZ12646915) was administered intravesically prior to a second inflation. Afferent activity was measured before and after administration of the cannabinoid compound or its vehicle. The effects of CB 1 receptor antagonist (AM251) on the AZ12646915 response were also analyzed. Cannabinoid receptor CB 1 mRNA was detected in the urinary bladder of the mouse. The protein was found in the urothelium, as well as in nerve fibers. CB 1 and P2X 3 receptors were found to be co-expressed in urothelial cells and in some nerve fibers. In addition, intravesical administration of a cannabinoid receptor agonist reduced the mechanically-evoked activity of bladder afferents in the pelvic nerve. This effect was abolished by the previous administration of the CB 1 antagonist AM251. These data demonstrate the presence of cannabinoid CB 1 receptor mRNA and the protein in the mouse urinary bladder. CB 1 and P2X 3 protein co-localization supports the hypothesis of an interaction between the cannabinoid and the purinergic systems in the transduction of sensory information in the urinary bladder. Finally, the reduction of nerve activity induced by cannabinoid-receptor activation implicates CB 1 receptors in the peripheral modulation of bladder afferent information.

Lung volumes and respiratory mechanics in elastase-induced emphysema in mice

Absolute lung volumes such as functional residual capacity, residual volume (RV), and total lung capacity (TLC) are used to characterize emphysema in patients, whereas in animal models of emphysema, the mechanical parameters are invariably obtained as a function of transrespiratory pressure (Prs). The aim of the present study was to establish a link between the mechanical parameters including tissue elastance (H) and airway resistance (Raw), and thoracic gas volume (TGV) in addition to Prs in a mouse model of emphysema. Using low-frequency forced oscillations during slow deep inflation, we tracked H and Raw as functions of TGV and Prs in normal mice and mice treated with porcine pancreatic elastase. The presence of emphysema was confirmed by morphometric analysis of histological slices. The treatment resulted in an increase in TGV by 51 and 44% and a decrease in H by 57 and 27%, respectively, at 0 and 20 cmH(2)O of Prs. The Raw did not differ between the groups at any value of Prs, but it was significantly higher in the treated mice at comparable TGV values. In further groups of mice, tracheal sounds were recorded during inflations from RV to TLC. All lung volumes but RV were significantly elevated in the treated mice, whereas the numbers and size distributions of inspiratory crackles were not different, suggesting that the airways were not affected by the elastase treatment. These findings emphasize the importance of absolute lung volumes and indicate that tissue destruction was not associated with airway dysfunction in this mouse model of emphysema.

Large volume axionic Swiss cheese inflation

Continuing with the ideas of (Section 4 of) [A. Misra, P. Shukla, Moduli stabilization, large-volume dS minimum without anti-D3-branes, (non-)supersymmetric black hole attractors and two-parameter Swiss cheese Calabi–Yau's, arXiv: 0707.0105 [hep-th], Nucl. Phys. B, in press], after inclusion of perturbative and non-perturbative α ′ corrections to the Kähler potential and (D1- and D3-) instanton generated superpotential, we show the possibility of slow roll axionic inflation in the large volume limit of Swiss cheese Calabi–Yau orientifold compactifications of type IIB string theory. We also include one- and two-loop corrections to the Kähler potential but find the same to be subdominant to the (perturbative and non-perturbative) α ′ corrections. The NS–NS axions provide a flat direction for slow roll inflation to proceed from a saddle point to the nearest dS minimum.

Electrical impedance tomography compared with thoracic computed tomography during a slow inflation maneuver in experimental models of lung injury*

To determine the validity of functional electric impedance tomography to monitor regional ventilation distribution in experimental acute lung injury, and to develop a simple electric impedance tomography index detecting alveolar recruitment. Randomized prospective experimental study. Academic research laboratory. Sixteen anesthetized, tracheotomized, and mechanically ventilated pigs. Acute lung injury was induced either by acid aspiration (direct acute lung injury) or by abdominal hypertension plus oleic acid injection (indirect acute lung injury) in ten pigs. Six pigs with normal lungs were studied as a control group and with endotracheal suction-related atelectasis. After 4 hrs of mechanical ventilation, a slow inflation was performed. During slow inflation, simultaneous measurements of regional ventilation by electric impedance tomography and dynamic computed tomography were highly correlated in quadrants of a transversal thoracic plane (r2 = .63-.88, p < .0001, bias <5%) in both direct and indirect acute lung injury. Variability between methods was lower in direct than indirect acute lung injury (11 +/- 2% vs. 18 +/- 3%, respectively, p < .05). Electric impedance tomography indexes to detect alveolar recruitment were determined by mathematical curve analysis of regional impedance time curves. Empirical tests of different methods revealed that regional ventilation delay, that is, time delay of regional impedance time curve to reach a threshold, correlated well with recruited volume as measured by CT (r2 = .63). Correlation coefficients in subgroups were r2 = .71 and r2 = .48 in pigs with normal lungs with and without closed suction related atelectasis and r2 = .79 in pigs subject to indirect acute lung injury, respectively, whereas no significant correlation was found in pigs undergoing direct acute lung injury. Electric impedance tomography allows assessment of regional ventilation distribution and recruitment in experimental models of direct and indirect acute lung injury as well as normal lungs. Except for pigs with direct acute lung injury, regional ventilation delay determined during a slow inflation from impedance time curves appears to be a simple index for clinical monitoring of alveolar recruitment.

On the supergravity origin of the minimally supersymmetric standard modelinflation

We consider the supergravity origin of the recently proposed minimally supersymmetricstandard model (MSSM) inflation, which relies on the existence of a saddle point along adimension 6 flat direction. We derive the conditions that the Kähler potential has to satisfyfor the saddle point to exist irrespective of the hidden sector vacuum expectation values.We show that these conditions are satisfied by a simple class of Kähler potentials, which wefind to have a form like those in various string theory compactifications. For thesepotentials, slow roll MSSM inflation requires no fine-tuning of the soft supersymmetrybreaking parameters.

A stochastic measure for eternal inflation

We use the stochastic approach to investigate a measure for slow roll eternal inflation. Theprobability for the universe to have a given Hubble radius can be calculated in this framework.In a solvable model, it is shown that the probability for the universe to evolve from a statewith a smaller Hubble radius to one with a larger Hubble radius is dominated by theclassical probability without the stochastic source, while the probability for the universe toevolve from a state with a larger Hubble radius to one with a smaller one is suppressed byexp(−ΔS), where the deSitter entropy S arises naturally in this stochastic approach.

Exchange-rate-based stabilization: Imperfect competition and supply-side effects

This paper studies exchange-rate-based stabilization programs in the context of a dynamic general equilibrium model for a small open economy that incorporates imperfect competition, a backward-looking wage setting, and an endogenous labor supply. In contrast to previous results, the analysis shows that a permanent disinflation leads to a sustained expansion in the domestic sector and a slow inflation convergence. This study also shows that a temporary stabilization replicates a “boom-recession cycle”. These results suggest that a backward-looking wage setting and an endogenous labor supply are the key ingredients for reproducing the stylized facts of exchange-rate-based stabilization.

Emerging Endovascular Therapies for Symptomatic Intracranial Atherosclerotic Disease

Marc Fisher MD Section Editor Over the past 2 decades there has been an exponential growth in the scope of disease processes amenable to neuroendovascular treatment. The number and sophistication of the available devices and correspondingly the number of patients undergoing treatment has expanded accordingly. The development and implementation of these new procedures has in some cases outpaced our ability to carefully assess their merits. In comparison to peripheral and coronary vascular disease, neurovascular lesions are less common and far more heterogeneous, ranging from acquired cerebrovascular ischemic disease to hemorrhagic congenital arteriovenous malformations. Each individual disease process (eg, cerebral aneurysm) is composed of a myriad of lesions with different anatomical and pathophysiological characteristics. The natural history of these lesions and their subtypes are likewise poorly defined. For these reasons, personal bias, institutional custom, and anecdotal experience rather than scientific evidence have played a dominant role in guiding therapy. We must move toward collaborative multi-center efforts, prospective data collection and well designed randomized controlled trials to mature as a field over the coming decades. In some ways, symptomatic intracranial atherosclerotic disease (SxICAD) represents an optimal disease process with which to establish this progress toward evidenced based treatment. SxICAD is considerably less heterogeneous than other cerebrovascular disease processes and is arguably best suited as a paradigm for study. In the current article we have attempted to review the available evidence describing the natural history of medically treated SxICAD to determine those patients best suited for invasive treatment strategies. We will also discuss the available treatment modalities which may represent viable options to medical therapy. These data form the basis for the design of future prospective multicenter studies to evaluate the relative merits of interventional treatment. Any invasive treatment strategy for symptomatic intracranial atherosclerosis must satisfy two criteria to establish viability as a …