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Strain dependance of microvascular failure and alveolar epithelium disruption during mechanical ventilation in normal open chest rats
No full textEffects of Heliox in Stable COPD Patients at Rest and during Exercise
Get PDFHeliox has been administered to stable chronic obstructive pulmonary disease (COPD) patients at rest and during exercise on the assumption that this low density mixture would have reduced work of breathing, dynamic hyperinflation, and, consequently, dyspnea sensation. Contrary to these expectations, beneficial effects of heliox in these patients at rest have been reported only sporadically, and the majority of the studies performed until now suggests that heliox is not a therapeutic option in spontaneously breathing resting COPD patients. On the other hand, when it is administered to COPD patients exercising at a constant work rate, heliox systematically decreases dyspnea sensation, and, often but not always, increases exercise tolerance. For these reasons, heliox has been evaluated as a non pharmacological tool to power rehabilitation programs. The conflicting results provided by the published trials probably point at a substantial heterogeneity of the COPD patients population in terms of respiratory mechanics and gas exchange. Therefore, further studies, aimed to the identification of mechanisms conditioning the response of exercising COPD patients to heliox, are warranted, before heliox administration, which is costly and cumbersome, can be routinely used in rehabilitation programs
Esophageal pressure as an estimate of average pleural pressure with lung or chest distortion in rats
Get PDFPressure-volume curves of the lungs and chest wall require knowledge of an effective ‘average’ pleural pressure (Pplav), and are usually estimated using esophageal pressure as PLes-V and PWes-V curves. Such estimates could be misleading when Ppl becomes spatially non-uniform with lung lavage or shape distortion of the chest. We therefore measured PLes-V and PWes-V curves in conditions causing spatial non-uniformity of Ppl in rats. PLes-V curves of normal lungs were unchanged by chest removal. Lung lavage depressed PLes-V but not PWes-V curves to lower volumes, and chest removal after lavage increased volumes at PL≥15 cmH2O by relieving distortion of the mechanically heterogeneous lungs. Chest wall distortion by ribcage compression or abdominal distension depressed PWes-V curves and PLes-V curves of normal lungs only at PL≥3 cmH2O. In conclusion, Pes reflects Pplav with normal and mechanically heterogeneous lungs. With chest wall distortion and dependent deformation of the normal lung, changes of PLes-V curves are qualitatively consistent with greater work of inflatio
Acute effects of long acting bronchodilators on small airways detected in COPD patients by single breath N2 test and lung P-V curve
Get PDFSmall airways represent the key factor of chronic obstructive pulmonary disease (COPD) pathophysiology. The effect of different classes of bronchodilators on small airways is still poorly understood and difficult to assess. Hence, the acute effects of tiotropium (18 μg) and indacaterol (150 μg) on closing volume (CV) and ventilation inhomogeneity were investigated and compared in 51 stable patients (mean age (SD): 70±7 years; 82% males) with moderate to very severe COPD. Patients underwent body-plethysmography, arterial blood gas-analysis, tidal expiratory flow limitation (EFL), dyspnea assessment, and simultaneous recording of single breath nitrogen test (SBN) and transpulmonary pressure-volume curve (PL-V), before and one hour after drug administration. The effects produced by indacaterol on each variable did not differ from those caused by tiotropium, independent of the severity of disease, assessed according to the GOLD scale, and the presence of EFL. Bronchodilators significantly decreased the slope of phase III and CV (-5±4% and -2.5±2.1%, both P<0.001), with an increase in both slope and height of phase IV, and of the anatomical dead space. Arterial oxygen pressure and saturation significantly improved (3±3 mmHg and 2±2%, both P<0.001); their changes negatively correlated with those of phase III slope (r=-0.659 and r=-0.454, both P<0.01). The vital capacity (VC) increased substantially but the PL-V/VC curve above CV was unaffected. In conclusion, bronchodilators reduce the heterogeneity of peripheral airway mechanical properties and the extent of their closure, with minor effects on critical closing pressure. This should lessen the risk of small airways damage and positively affect gas exchange
Mixed lubrication after rewetting of blotted pleural mesothelium
Get PDFCoefficient of kinetic friction (μ) of pleural mesothelium blotted with filter paper, and rewetted with Ringer solution markedly increases; this increase is removed if a sufficient amount of sialomucin or hyaluronan is added to Ringer (Bodega et al., 2012. Respiratory Physiology and Neurobiology 180, 34–39). In this research we found that μ of pleural mesothelium blotted, rewetted, and sliding at physiological velocities and loads, decreased with increase of velocity, mainly at low velocities. Despite this decrease, μ at highest velocity was still double that before blotting. With small concentration of sialomucin or hyaluronan μ was markedly smaller at each velocity, decreased less with increase of velocity, and at highest velocity approached preblotting value. These findings indicate a regime of mixed lubrication in post-blotting Ringer, at variance with boundary lubrication occurring before blotting or postblotting with sufficient macromolecule addition. Greater roughness of mesothelial surface, caused by blotting, likely induces zones of elastohydrodynamic lubrication, which increase with velocity, while contact area decrease
Positive -versus negative- pressure ventilation in healthy rats
No full textBackground
Observations in healthy rats and mice (Moriondo, A. et al. J Appl Physiol 2007; 103: 747-756; Vaneker, M. et al. Anesthesiology 2007; 107: 419-426) suggest that conventional positive-pressure ventilation with normal tidal volumes worsens lung mechanics and induces cytokine release.
Aims
To assess whether in normal rats, different kinds of mechanical ventilation produce adverse effects as compared to spontaneous ventilation.
Methods
Anesthetized, tracheotomized rats were randomly assigned to 3 groups of 6 animals each: spontaneous breathing, positive-pressure ventilation, and negative-pressure ventilation group. Duration of ventilation (4 h) and mean tidal volume (6.8 ml/kg) were the same for all groups. Dynamic lung elastance (E) and resistance (R) were assessed throughout the test period. The left lung was used for the measure of the wet-to-dry (W/D) ratio and collection of bronchoalveolar lavage fluid (BALF), while the right lung was fixed for histologic assessment (mean linear intercept, bronchiolar injury score, lesioned bronchiolar-alveolar attachments). Cytokines (TNF- IL-1, IL-6, MIP-2, and IL-10) were measured in BALF and serum. Six additional animals, killed immediately, served as control.
Results
During the test period, E moderately increased (+16%), independent of the type of ventilation, while R remained unchanged. W/D ratio and cytokine levels in serum and BALF did not differ among groups. Relative to control, only serum levels of IL-6 and IL-10 were increased. Histologic indexes were similar to control in all groups.
Conclusion
No deleterious effect of mechanical ventilation was found in comparison to spontaneous breathing, independent of the modality with which mechanical ventilation was performed
Cost of breathing during exercise
No full textIn healthy subjects, the metabolic cost of ventilation is small during rest or moderate exercise, but increases during heavy exercise, reaching ~10% of the total energy expenditure at peak exercise. Moreover, activation of metaboreceptors in the respiratory muscles during heavy exercise may trigger an increase of the sympathetic outflow to the locomotor muscles, blunting the increase of the bloodflow and limiting the performance. The cost of ventilation may become substantial in the presence of a pulmonary pathology, as chronic obstructive pulmonary disease.
Despite its importance in physiological and pathological conditions, the measurement of the cost of breathing remains a challenge, as suggested by the wide range of values reported in the literature. To measure the cost of breathing via indirect calorimetry, ventilation should be increased while maintaining non-respiratory oxygen consumption constant. As the fraction of expired oxygen increases, measurement of oxygen consumption becomes problematic, because the relation between alveolar ventilation and alveolar partial pressure of oxygen becomes almost flat, and small errors in measuring expired gas composition produce big errors in the calculation of oxygen consumption. Additionally, the modality of ventilation may be strikingly different according to the stimulus which elicited the increase of ventilation, namely exercise or the addition of a dead space or of hypercapnic mixtures. Mimicking at rest the breathing pattern recorded at various levels of exercise may improve the accuracy of the estimation of the cost of breathing, but this method is technically difficult and requires a high level of cooperation from the experimental subject
Biochemical and physiological principles on CO2
No full textThe patholophysiological mechanism related to the decap application have been discussed
Il Fisiologo e la ventilazione non invasiva: un punto di vista differente?
No full textUtilizzando dati acquisiti su un modello animale, sono stati discussi gli effetti della ventilazione meccanica a pressione positiva e negativi, rispetto a quelli della ventilazione spontanea
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