Optical clearing: impact of optical and dielectric properties of clearing solutions on pulmonary tissue mechanics.

Optical clearing allows tissue visualization under preservation of organ integrity. Optical clearing of organs with a physiological change in three-dimensional geometry (such as the lung) would additionally allow visualization of macroscopic and microscopic tissue geometry. A prerequisite, however, is the preservation of the native tissue mechanics of the optically cleared lung tissue.

The Equilibration of PCO2 in Pigs Is Independent of Lung Injury and Hemodynamics.

Objectives: In mechanical ventilation, normoventilation in terms of PCO2 can be achieved by titration of the respiratory rate and/or tidal volume. Although a linear relationship has been found between changes in respiratory rate and resulting changes in end-tidal cO2 (△PetCO2) as well as between changes in respiratory rate and equilibration time (teq) for mechanically ventilated patients without lung injury, it is unclear whether a similar relationship holds for acute lung injury or altered hemodynamics.

Design: We performed a prospective randomized controlled animal study of the change in PetCO2 with changes in respiratory rate in a lung-healthy, lung-injury, lung-healthy + altered hemodynamics, and lung-injury + altered hemodynamics pig model.

Endomicroscopic analysis of time- and pressure-dependent area of subpleural alveoli in mechanically ventilated rats.

We investigated the effects of recruitment maneuvers on subpleural alveolar area in healthy rats. 36 mechanically ventilated rats were allocated to either ZEEP-group or PEEP - 5cmH2O - group. The subpleural alveoli were observed using a transthoracal endoscopic imaging technique.

Time and volume dependence of dead space in healthy and surfactant-depleted rat lungs during spontaneous breathing and mechanical ventilation.

Volumetric capnography is a standard method to determine pulmonary dead space. Hereby, measured carbon dioxide (CO2) in exhaled gas volume is analyzed using the single-breath diagram for CO2. Unfortunately, most existing CO2 sensors do not work with the low tidal volumes found in small animals.

Endoscopic imaging to assess alveolar mechanics during quasi-static and dynamic ventilatory conditions in rats with noninjured and injured lungs.

Objectives: Although global respiratory mechanics are usually used to determine the settings of mechanical ventilation, this approach does not adequately take into account alveolar mechanics. However, it should be expected that the ventilatory condition (quasi-static vs. dynamic) and lung condition (noninjured vs.

Time-dependent recruitment effects in ventilated healthy and lung-injured rats: "recruitment-memory".

We investigated the sustained effects of recruitment manoeuvres in terms of "recruitment memory" in healthy and lung injured rats. 46 ventilated rats were allocated to either the control (sham) or the lavage group. Two consecutive low-flow manoeuvres were performed before sham/lavage and hourly during a 2-h-observation period.

Locally measured shear moduli of pulmonary tissue and global lung mechanics in mechanically ventilated rats.

This study was aimed at measuring shear moduli in vivo in mechanically ventilated rats and comparing them to global lung mechanics. Wistar rats (n = 28) were anesthetized, tracheally intubated, and mechanically ventilated in supine position. The animals were randomly assigned to the healthy control or the lung injury group where lung injury was induced by bronchoalveolar lavage.

Effects of intra-abdominal pressure on respiratory system mechanics in mechanically ventilated rats.

We investigated the effects of intra-abdominal pressure on respiratory system compliance at different PEEP levels. 20 ventilated rats underwent four pressure levels (7, 9, 11, 13 mm Hg) of helium pneumoperitoneum and were allocated to one of the four PEEP groups (0, 3, 6 and 9 cm H(2)O). From the expiratory pressure-volume curve the mathematical inflection point (MIP) was calculated.

Morphometry of subpleural alveoli may be greatly biased by local pressure changes induced by the microscopic device.

Microscopy of subpleural alveoli has become an important technique to analyze alveolar morphology during mechanical ventilation. Mere contact of a microscope with the lung, however, may alter the local pressure at the pleural surface and thus the transmural pressure of the alveoli under view. The effect of local pleural pressure changes on alveolar morphology during microscopy has not been systematically evaluated hitherto.

Intravital microscopy of subpleural alveoli via transthoracic endoscopy.

Transfer of too high mechanical energy from the ventilator to the lung's alveolar tissue is the main cause for ventilator-induced lung injury (VILI). To investigate the effects of cyclic energy transfer to the alveoli, we introduce a new method of transthoracic endoscopy that provides morphological as well as functional information about alveolar geometry and mechanics. We evaluate the new endoscopic method to continuously record images of focused subpleural alveoli.