Ventilator-associated lung injury superposed to oleic acid infusion or surfactant depletion: histopathological characteristics of two porcine models of acute lung injury.

BACKGROUND: The pathophysiological concept of acute lung injury (ALI) in combination with ventilator-associated lung injury (VALI) is still unclear. We characterized the histopathological features of intravenous injection of oleic acid (OAI) and lung lavage (LAV) combined with VALI. METHODS: Pigs were randomized to the control, LAV or OAI group and ventilated by pressure-controlled ventilation. MEASUREMENTS INCLUDED: haemodynamics, spirometry, blood gas analysis, lung wet-to-dry weight ratio (W/D), total protein content in broncho-alveolar lavage fluid (BALF), and lung pathological description and scoring. RESULTS: Five hours after lung injury induction, gas exchange was significantly impaired in both the OAI and the LAV groups. Compared to controls, we found an increase in W/D and histopathological total injury scores in both the LAV and OAI groups and an increase in BALF total protein content in the OAI group. In contrast to the LAV group, the OAI group showed septal necrosis and alveolar oedema. Both groups exhibited dorsal and caudal atelectasis and interstitial oedema. In addition, the OAI group demonstrated a propensity to dorsal necrosis and congestion whereas the LAV group tended to develop ventral overdistension and barotrauma. CONCLUSIONS: This study presents a comparison of porcine OAI and LAV models combined with VALI, providing information for study design in research on ALI.

The impact of vessel and catheter position on the measurement accuracy in catheter-based quantitative coronary angiography.

BACKGROUND: The calculation of absolute artery dimensions in quantitative coronary angiography is usually carried out by catheter calibration. It is based on the proportional comparison of the dimension of the imaged artery segment to the dimension of the imaged angiographic catheter of known size. This calibration method presumes an identical radiographic magnification between angiographic catheter and artery segment of interest. However, due to the different intrathoracic location of both objects the radiographic magnification or calibration factor is often not identical for a given angiographic projection. The aim of this study was to quantify the magnification error (out-of-plane magnification error) for the major coronary artery segments imaged in frequently used angiographic projections. METHODS: The intrathoracic spatial location of 468 coronary segments (RCA 196, LAD 156, LCX 116) and their respective coronary catheters were established with biplane angiography and known imaging geometry data. The error in the radiographic magnification or calibration factor was then calculated for all 936 monoplane projections using the spatial coordinates and imaging geometry data. RESULTS: The mean magnitude of magnification error was 4% within all 936 measurements. The magnitude and direction of error varied with the lesion localization and the angiographic projection angle (range -12.6% to +10.6%). The error characteristics could be described with six typical error groups by stratifying the data according to the three main coronaries and two angiographic planes. In 24% of measurements, the magnification error exceeded the 5.2% error limit acceptable for reference vessel sizing. Measurements of left coronary arteries were mainly affected by it. CONCLUSION: The magnification error contributes to the calibration error in measuring arterial dimensions by quantitative angiography. This error may affect the reliability of clinical studies and the proper sizing of interventional devices. These findings could be used to improve current error correction algorithms in order to reduce the effect of the magnification error in measuring arterial dimensions.

Neurotrophic influence on lobster skeletal muscle.

The correlation between histochemical properties of muscle fibers and the pattern of innervation by the two motor neurons was studied in the asymmetric claw closer muscles of the lobster. The closer muscle of the cutter claw is composed of 65 percent fast muscle fibers and 35 percent slow muscle fibers, whereas that in the crusher claw has all slow muscle fibers. In both claws, myofibrillar adenosinetriphosphatase activity was independent of the pattern of innervation. Oxidative capacity, as measured by reduced nicotinamide adenine dinucleotide activity, was correlated with motor axon presence: Muscle fibers innervated solely by the "fast" motor axon had low oxidative capacity, muscle fibers receiving only the slow motor axon had very high oxidative capacity, and fibers innervated by both axons had intermediate properties. The data suggest that the motor neurons may exert trophic influences that control certain muscle fiber properties but not others.