Comparison between neurally-assisted, controlled, and physiologically variable ventilation in healthy rabbits.

BACKGROUND: Various ventilation strategies have been proposed to reduce ventilation-induced lung injury that occurs even in individuals with healthy lungs. We compared new modalities based on an individualised physiological variable ventilation model to a conventional pressure-controlled mode. METHODS: Rabbits were anaesthetised and ventilated for up to 7 h using pressure-controlled ventilation with (Group PCS, n=10), and without (Group PC, n=10) regular sighs. Variable ventilation in the other two groups was achieved via a pre-recorded spontaneous breathing pattern [Group physiologically variable ventilation (PVV), n=10] or triggered by the electrical activity of the diaphragm [Group neurally adjusted ventilation assist (NAVA), n=9]. Respiratory elastance, haemodynamic profile, and gas exchange were assessed throughout the ventilation period. Cellular profile, cytokine content of bronchoalveolar lavage fluid, and wet-to-dry lung weight ratio (W/D) were determined after protocol completion. Lung injury scores were obtained from histological analysis. RESULTS: Marked deteriorations in elastance were observed (median and 95% confidence interval) in Group PC [48.6 (22)% increase from baseline], while no changes were detected in Groups PCS [3.6 (8.1)%], PVV [18.7 (13.2)%], and NAVA [-1.4 (12.2)%]. In comparison with Group PC, Group PVV had a lower lung injury score [0.29 (0.02) compared with 0.36 (0.05), P<0.05] and W/D ratio [5.6 (0.1) compared with 6.2 (0.3), P<0.05]. There was no difference in blood gas, haemodynamic, or inflammatory parameters between the groups. CONCLUSIONS: Individualised PVV based on a pre-recorded spontaneous breathing pattern provides adequate gas exchange and promotes a level of lung protection. This ventilation modality could be of benefit during prolonged anaesthesia, in which assisted ventilation is not possible because of the absence of a respiratory drive.

Quantitative Imaging of Regional Aerosol Deposition, Lung Ventilation and Morphology by Synchrotron Radiation CT.

To understand the determinants of inhaled aerosol particle distribution and targeting in the lung, knowledge of regional deposition, lung morphology and regional ventilation, is crucial. No single imaging modality allows the acquisition of all such data together. Here we assessed the feasibility of dual-energy synchrotron radiation imaging to this end in anesthetized rabbits; both in normal lung (n = 6) and following methacholine (MCH)-induced bronchoconstriction (n = 6), a model of asthma. We used K-edge subtraction CT (KES) imaging to quantitatively map the regional deposition of iodine-containing aerosol particles. Morphological and regional ventilation images were obtained, followed by quantitative regional iodine deposition maps, after 5 and 10 minutes of aerosol administration. Iodine deposition was markedly inhomogeneous both in normal lung and after induced bronchoconstrition. Deposition was significantly reduced in the MCH group at both time points, with a strong dependency on inspiratory flow in both conditions (R2 = 0.71; p < 0.0001). We demonstrate for the first time, the feasibility of KES CT for quantitative imaging of lung deposition of aerosol particles, regional ventilation and morphology. Since these are among the main factors determining lung aerosol deposition, we expect this imaging approach to bring new contributions to the understanding of lung aerosol delivery, targeting, and ultimately biological efficacy.

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.

[Fibro-osseous lesion of the central nervous system]. / A központi idegrendszer fibroosseosus laesiója.

The case of a 53-year-old woman with headache and progressive right sided decline of visual acuity is reported. Computed tomography scans of the brain revealed multiple circumscribed foci of mineralization located over the left frontal and parietal, as well as the right central brain parenchyma. Surgical sampling of the left frontal lesion yielded a conglomerate composed of mineralized vessels, myriad of psammoma bodies, and metaplastic lamellar bone entangled within poorly cellular collagen fibers. No evidence was found of an underlying vascular malformation or tumor, nor was there evidence of parenchymal necrosis of infectious origin. On account of the organoid association of the mesenchymal elements and the mineralized moiety, the lesion was consistent with fibro-osseous lesion of the central nervous system. Also known as "calcifying pseudotumor" of the brain, the origin of this exceedingly rare condition is, as yet, unknown. By analogy, its pathogenesis is likely to involve mechanisms underlying tumoral calcinosis of soft tissues.