Search results for "Pulmonary ventilation"
showing 10 items of 37 documents
Sputum metalloproteinase-9/tissue inhibitor of metalloproteinase-1 ratio correlates with airflow obstruction in asthma and chronic bronchitis
1998
Asthma and chronic bronchitis are inflammatory diseases with extracellular matrix (ECM) remodeling and collagen deposition. Collagen homeostasis is controlled by metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). We evaluated MMP and TIMP balance in induced sputum of 10 control, 31 untreated asthmatic, and 16 chronic bronchitic subjects. We first performed zymographic analysis to identify the profile of MMPs. Zymography revealed a similar MMPs profile in all populations studied and that MMP-9 was the major enzyme released. We then measured, using enzyme immunoassay, the concentrations of MMP-9 and of its inhibitor TIMP-1 and evaluated whether airflow limitation m…
Autonomic regulation of nasal vessels during changes in body position
1994
The effects of postural changes on nasal airflow and nasal capillary blood flow were investigated in 15 healthy volunteers. Measurements were performed following nasal application of saline solution (control), the alpha-1 receptor antagonist prazosin, the alpha-2 receptor antagonist yohimbine, and after application of both prazosin and yohimbine. Nasal airflow in the control experiments did not significantly differ in the upright (362 +/- 166 ml/s), dorsally recumbent (350 +/- 167 ml/s) and 70 degrees head down position (311 +/- 167 ml/s). Following application of prazosin, nasal airflow was reduced to 223 +/- 121 ml/s in the upright position. Prazosin treatment significantly reduced nasal …
Airways Hyperresponsiveness and the Effects of Lung Inflation
2001
Lung inflation has a beneficial effect on the airways of healthy subjects. It acts as a bronchoprotector, that is to prevent bronchoconstriction, and as a bronchodilator, in that it reverses bronchial obstruction. The bronchoprotective effect of deep inspiration is more potent than the bronchodilatory one, and the two phenomena appear to advocte different mechanisms. Asthmatics and rhinitics with airways hyperresponsiveness show an impairment in bronchoprotection induced by deep breaths, whereas the bronchodilatory effect, although reduced, is still effective. The lack of the bronchoprotective effect of deep inspiration may contribute to the development of airways hyperresponsiveness. The m…
Dynamic computed tomography: a novel technique to study lung aeration and atelectasis formation during experimental CPR
2002
Objective: To develop an image based technique to study the effect of different ventilatory strategies on lung ventilation and alveolar recruitment during cardiopulmonary resuscitation (CPR). Design: (1) Technical development of the following components: (a) construction of an external chest compression device, which does not interfere with CT imaging, and (b) development of a software tool to detect lung parenchyma automatically and to calculate radiological density parameters. (2) Feasibility studies: three strategies of CPR ventilation were performed and imaged in one animal each (pigs, 25 kg): volume-constant ventilation (VCV), no ventilation, or continuous airway pressure (CPAP). One m…
Differential contribution of dead space ventilation and low arterial pCO2 to exercise hyperpnea in patients with chronic heart failure secondary to i…
2003
In chronic heart failure (CHF), the abnormally large ventilatory response to exercise (VE/VCO(2) slope) has 2 conceptual elements: the requirement of restraining arterial partial pressure of carbon dioxide (pCO(2)) from increasing (because of an increased ratio between increased physiologic dead space and tidal volume [VD/VT]) and the depression of arterial pCO(2) by further increased ventilation, which necessarily implies an important non-carbon dioxide stimulus to ventilation. We aimed to assess the contribution of these 2 factors in determining the elevated VE/VCO(2) slope in CHF. Thirty patients with CHF underwent cardiopulmonary exercise testing (age 65 +/- 11 years, left ventricular e…
Assessment of a single-acquisition imaging sequence for oxygen-sensitive (3)He-MRI.
2001
MRI of the lungs using hyperpolarized helium-3 (3He) allows the determination of intrapulmonary oxygen partial pressures (pO2). The need to separate competing processes of signal loss has hitherto required two different imaging series during two different breathing maneuvers. In this work, a new imaging strategy to measure pO2 by a single series of consecutive scans is presented. The feasibility of the method is demonstrated in three healthy human volunteers. Maps and histograms of intrapulmonary pO2 are calculated. Changes in the oxygen concentration of the inhaled gas mixture are well reproduced in the histograms. Monte Carlo (MC) simulations of the temporal evolution of 3He hyperpolariza…
Assessment of regional ventilation distribution: comparison of vibration response imaging (VRI) with electrical impedance tomography (EIT)
2013
BACKGROUND: Vibration response imaging (VRI) is a bedside technology to monitor ventilation by detecting lung sound vibrations. It is currently unknown whether VRI is able to accurately monitor the local distribution of ventilation within the lungs. We therefore compared VRI to electrical impedance tomography (EIT), an established technique used for the assessment of regional ventilation. METHODOLOGY/PRINCIPAL FINDINGS: Simultaneous EIT and VRI measurements were performed in the healthy and injured lungs (ALI; induced by saline lavage) at different PEEP levels (0, 5, 10, 15 mbar) in nine piglets. Vibration energy amplitude (VEA) by VRI, and amplitudes of relative impedance changes (rel.ΔZ) …
Contrast-enhanced MRI of the lung
2000
The lung has long been neglected by MR imaging. This is due to unique intrinsic difficulties: (1) signal loss due to cardiac pulsation and respiration; (2) susceptibility artifacts caused by multiple air-tissue interfaces; (3) low proton density. There are many MR strategies to overcome these problems. They consist of breath-hold imaging, respiratory and cardiac gating procedures, use of short repetition and echo times, increase of the relaxivity of existing spins by administration of intravenous contrast agents, and enrichment of spin density by hyperpolarized noble gases or oxygen. Improvements in scanner performance and frequent use of contrast media have increased the interest in MR ima…
Effect of lung mechanics on mechanically assisted flows and volumes.
2004
To correlate the air flows generated by mechanical insufflation-exsufflation as a function of pressure delivery in a lung model at two pulmonary compliance and three airway resistance settings.With each combination of pulmonary compliances of 25 and 50 ml/cm H2O and airway resistances of 6, 11, and 17 cm H2O/liter/sec, ten cycles of mechanical insufflation-exsufflation were applied using pressure deliveries of 40 to -40, 50 to -50, 60 to -60, and 70 to -70 cm H2O. The resulting peak exsufflation flows and volumes were recorded.In a multivariate analysis, the pulmonary compliance, airway resistance, and pressure delivery were all found to significantly affect exsufflation flows and volumes s…
Bronchial hyperresponsiveness in children with atopic rhinitis: a 7-year follow-up
2004
Background: A high prevalence of bronchial hyperresponsiveness (BHR) was found in atopic subjects with rhinitis. Those subjects may be at higher risk for developing bronchial asthma. We evaluated, in a 7-year follow-up, BHR and atopy in a homogeneous population of nonasthmatic children with allergic rhinitis (AR), and their role in asthma development. Methods: Twenty-eight children (6–15 years) with AR were studied. At enrollment (T0), skin tests, total serum IgE assay, peak expiratory flow (PEF) monitoring and methacholine (Mch) bronchial challenge were performed. BHR was computed as the Mch dose causing a 20% forced expiratory volume (FEV)1 fall (PD20FEV1) and as dose–response slope (DR…