Measurement of aggregate size distribution by inversion of angular light scattering

The aim of this work is to propose a new method for determining the size distribution of submicronic particles by inversion of the measured angular scattering of light. This method relies on the determination of a function Rg*. by angular scattering. The variation of this function informs us about the polydispersity of the aggregates size. We show that, by supposing the nature of the size distributions (lognormal), it is possible to determine the governing parameters of these distributions

Relationships between respiratory and airway resistances and activity-related dyspnea in patients with chronic obstructive pulmonary disease

Bruno Mahut1,2, Aurore Caumont-Prim3,4, Laurent Plantier1,5, Karine Gillet-Juvin1,6, Etienne Callens1, Olivier Sanchez5,6, Brigitte Chevalier-Bidaud3, Plamen Bokov1, Christophe Delclaux1,5,71Assistance Publique – Hôpitaux de Paris (AP-HP), Hôpital Européen Georges Pompidou, Service de Physiologie – Clinique de la Dyspnée, F-75015 Paris, France; 2Cabinet La Berma, 4 avenue de la Providence; F-92160 Antony, France; 3AP-HP, Hôpital Européen Georges Pompidou, Unité d'Épidémiologie et de Recherche Clinique, F-75015 Paris, France; 4INSERM, Centre d'Investigation Épidémiologique 4, F-75015 Paris, France; 5Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, F-75015 Paris, France; 6AP-HP, Hôpital Européen Georges Pompidou, Service de Pneumologie; F-75015 Paris, France; 7CIC 9201 Plurithématique, Hôpital Européen Georges Pompidou, F-75015 Paris, FranceBackground: The aims of the study were: (1) to compare numerical parameters of specific airway resistance (total, sRawtot, effective, sRaweff and at 0.5 L • s-1, sRaw0.5) and indices obtained from the forced oscillation technique (FOT: resistance extrapolated at 0 Hz [Rrs0 Hz], mean resistance [Rrsmean], and resistance/frequency slope [Rrsslope]) and (2) to assess their relationships with dyspnea in chronic obstructive pulmonary disease (COPD).Methods: A specific statistical approach, principal component analysis that also allows graphic representation of all correlations between functional parameters was used. A total of 108 patients (mean ± SD age: 65 ± 9 years, 31 women; GOLD stages: I, 14; II, 47; III, 39 and IV, 8) underwent spirometry, body plethysmography, FOT, and Medical Research Council (MRC) scale assessments.Results: Principal component analysis determined that the functional parameters were described by three independent dimensions (airway caliber, lung volumes and their combination, specific resistance) and that resistance parameters of the two techniques were not equivalent, obviously. Correlative analyses further showed that Rawtot and Raweff (and their specific resistances) can be considered as equivalent and correlated with indices that are considered to explore peripheral airways (residual volume (RV), RV/ total lung capacity (TLC), Rrsslope), while Rrsmean and Raw0.5 explored more central airways. Only specific resistances taking into account the specific resistance loop area (sRawtot and sRaweff) and Rrsslope were statistically linked to dyspnea.Conclusion: Parameters obtained from both body plethysmography and FOT can explore peripheral airways, and some of these parameters (sRawtot, sRaweff, and Rrsslope) are linked to activity-related dyspnea in moderate to severe COPD patients.Keywords: body plethysmography, forced oscillation technique, principal component analysi

Granulocytic myeloid-derived suppressor cells inversely correlate with plasma arginine and overall survival in critically ill patients

Summary Critically ill patients display a state of immunosuppression that has been attributed in part to decreased plasma arginine concentrations. However, we and other authors have failed to demonstrate a clinical benefit of L-arginine supplementation. We hypothesize that, in these critically ill patients, these low plasma arginine levels may be secondary to the presence of granulocytic myeloid-derived suppressor cells (gMDSC), which express arginase known to convert arginine into nitric oxide (NO) and citrulline. Indeed, in a series of 28 non-surgical critically ill patients, we showed a dramatic increase in gMDSC compared to healthy subjects (P = 0·0002). A significant inverse correlation was observed between arginine levels and gMDSC (P = 0·01). As expected, gMDSC expressed arginase preferentially in these patients. Patients with high gMDSC levels on admission to the medical intensive care unit (MICU) presented an increased risk of death at day 7 after admission (P = 0·02). In contrast, neither plasma arginine levels, monocytic MDSC levels nor neutrophil levels were associated with overall survival at day 7. No relationship was found between body mass index (BMI) or simplified acute physiology score (SAPS) score, sequential organ failure assessment (SOFA) score or gMDSC levels, eliminating a possible bias concerning the direct prognostic role of these cells. As gMDSC exert their immunosuppressive activity via multiple mechanisms [production of prostaglandin E2 (PGE2), interleukin (IL)-10, arginase, etc.], it may be more relevant to target these cells, rather than simply supplementing with L-arginine to improve immunosuppression and its clinical consequences observed in critically ill patients.</jats:p

Assessment of five screening strategies for optimal detection of carriers of third-generation cephalosporin-resistant Enterobacteriaceae in intensive care units using daily sampling

AbstractThere is no consensus on optimal screening procedures for multidrug-resistant Enterobacteriaceae (MDRE) in intensive care units (ICUs). Therefore, we assessed five strategies for the detection of extended-spectrum beta-lactamase (ESBL) and high-level expressed AmpC cephalosporinase (HL-CASE) producers. During a 3-month period, a rectal screening swab sample was collected daily from every ICU patient, from the first 24 h to the last day of ICU stay. Samples were plated on MDRE-selective media. Bacteria were identified using MALDI-TOF mass spectrometry and antibiograms were performed using disk diffusion. MDREs were isolated from 682/2348 (29.0%) screening samples collected from 93/269 (34.6%) patients. Incidences of patients with ESBL and HL-CASE producers were 17.8 and 19.3 per 100 admissions, respectively. In 48/93 patients, MDRE carriage was intermittent. Compared with systematic screening at admission, systematic screening at discharge did not significantly increase the rate of MDRE detection among the 93 patients (62% vs. 70%). In contrast, screening at admission and discharge, screening at admission and weekly thereafter, and screening at admission and weekly thereafter and at discharge significantly increased MDRE detection (77%, p 0.02; 76%, p 0.01; 86%, p <0.001, respectively). The difference in MDRE detection between these strategies relies essentially on the levels of detection of patients with HL-CASE producers. The most reasonable strategy would be to collect two samples, one at admission and one at discharge, which would detect 87.5% of the ESBL strains, 67.3% of the HL-CASE strains and 77.4% of all MDRE strains. This study should facilitate decision-making concerning the most suitable screening policy for MDRE detection in a given ICU setting