Dynamic Mechanical Interactions Between Neighboring Airspaces Determine Cyclic Opening and Closure in Injured Lung

OBJECTIVES:: Positive pressure ventilation exposes the lung to mechanical stresses that can exacerbate injury. The exact mechanism of this pathologic process remains elusive. The goal of this study was to describe recruitment/derecruitment at acinar length scales over short-time frames and test the hypothesis that mechanical interdependence between neighboring lung units determines the spatial and temporal distributions of recruitment/derecruitment, using a computational model. DESIGN:: Experimental animal study. SETTING:: International synchrotron radiation laboratory. SUBJECTS:: Four anesthetized rabbits, ventilated in pressure controlled mode. INTERVENTIONS:: The lung was consecutively imaged at ~ 1.5-minute intervals using phase-contrast synchrotron imaging, at positive end-expiratory pressures of 12, 9, 6, 3, and 0 cm H2O before and after lavage and mechanical ventilation induced injury. The extent and spatial distribution of recruitment/derecruitment was analyzed by subtracting subsequent images. In a realistic lung structure, we implemented a mechanistic model in which each unit has individual pressures and speeds of opening and closing. Derecruited and recruited lung fractions (Fderecruited, Frecruited) were computed based on the comparison of the aerated volumes at successive time points. MEASUREMENTS AND MAIN RESULTS:: Alternative recruitment/derecruitment occurred in neighboring alveoli over short-time scales in all tested positive end-expiratory pressure levels and despite stable pressure controlled mode. The computational model reproduced this behavior only when parenchymal interdependence between neighboring acini was accounted for. Simulations closely mimicked the experimental magnitude of Fderecruited and Frecruited when mechanical interdependence was included, while its exclusion gave Frecruited values of zero at positive end-expiratory pressure greater than or equal to 3 cm H2O. CONCLUSIONS:: These findings give further insight into the microscopic behavior of the injured lung and provide a means of testing protective-ventilation strategies to prevent recruitment/derecruitment and subsequent lung damage

A mean body temperature of 37 degrees C for incubated preterm infants is associated with lower energy costs in the first 11days of life

International audienceAimThis randomised trial compared the energy costs of providing incubated preterm infants born before 32weeks of gestation with homeothermia using either air temperature control (ATC) or skin servocontrol (SSC). MethodsWe studied 38 incubated preterm infants for the first 11days of life, calculating the frequency of hypothermia (37.5 degrees C) and thermal challenge, together with energy costs, based on a change in incubator air temperature of 2 degrees C above or below thermoneutrality. ResultsThe daily mean incubator air temperature was higher in ATC than SSC (p<0.05) for the first 6days, and the mean body temperature was higher in ATC (37.00.03 degrees C) than SSC (36.8 +/- 0.02; p<0.01) over the whole study period. The frequency of moderate hyperthermia was higher in ATC (p<0.001), whereas warm and cold thermal challenges were higher in SSC (p<0.001). The two groups did not differ in terms of energy costs. The time to recover birthweight was shorter in ATC (p<0.05). ConclusionIn incubators using ATC, a body temperature of 37 degrees C was associated with lower energy costs and greater weight gain at 11days of life for preterm infants. Future studies should test SSC shielded abdominal skin temperature set to 37 degrees C

Intracranial suppurative complications of ear, nose and throat infections: A single-centre cohort study of 65 patients

International audienc

Imaging Intra-Breath Cyclic Changes In Regional Pulmonary Blood Volume: Effect Of Peep, Tidal Volume And Gravity Gravity

International Conference of the American-Thoracic-Society (ATS), Washington, DC, MAY 19-24, 2017International audienc

Diffusion-Convection Interaction As A Cause Of Uneven Gas Distribution In Rabbit Lung

International Conference of the American-Thoracic-Society (ATS), Denver, CO, MAY 15-20, 2015International audienc

Oscillatory Measurements Of Upper Airway Casts Reconstructed From CT Images

International Conference of the American-Thoracic-Society (ATS), San Francisco, CA, MAY 13-18, 2016International audienc

Oscillatory Measurements Of Upper Airway Casts Reconstructed From CT Images

International Conference of the American-Thoracic-Society (ATS), San Francisco, CA, MAY 13-18, 2016International audienc