Endotoxemia increases relative perfusion to dorsal-caudal lung regions.

Changes in the spatial distribution of perfusion during acute lung injury and their impact on gas exchange are poorly understood. We tested whether endotoxemia caused topographical differences in perfusion and whether these differences caused meaningful changes in regional ventilation-to-perfusion ratios and gas exchange. Regional ventilation and perfusion were measured in anesthetized, mechanically ventilated pigs in the prone position before and during endotoxemia with the use of aerosolized and intravenous fluorescent microspheres. On average, relative perfusion halved in ventral and cranial lung regions, doubled in caudal lung regions, and increased 1.5-fold in dorsal lung regions during endotoxemia. In contrast, there were no topographical differences in perfusion before endotoxemia and no topographical differences in ventilation at any time point. Consequently, endotoxemia increased regional ventilation-to-perfusion ratios in the caudal-to-cranial and dorsal-to-ventral directions, resulting in end-capillary PO2 values that were significantly lower in dorsal-caudal than ventral-cranial regions. We conclude that there are topographical differences in the pulmonary vascular response to endotoxin that may have important consequences for gas exchange in acute lung injury.

Cerebral blood flow determinations using fluorescent microspheres: variations on the sedimentation method validated.

We validate a modification of the sedimentation method for measuring fluorescent microspheres (FM) that improves the determination of regional cerebral blood flow (rCBF). Our FM method for rCBF determination is compared to the radioactive microspheres (RM) method for rCBF measurement by simultaneous injection of one radioactive and two fluorescent labeled doses, at two separate time points, into the left ventricle of a pig. The pig was killed, the brain and spinal cord removed, and divided into 92 pieces averaging 0.83 g. Our modifications to FM analysis by sedimentation includes: 2 instead of 1 week of autolysis, pellet washing with 1% Triton X-100 instead of 0.25% Tween 80, phosphate buffer addition during rinse, fluorescent dye extraction using 2-ethoxyethylacetate instead of 2-(2-ethoxyethoxy)ethyl acetate and polypropylene instead of glass tubes. Comparing rCBF using Sc46 RM, to yellow-green and orange FM, yielded mean differences of 0.026 and 0.021 ml/min per piece, respectively. Sn(113) RM compared to blue-green and scarlet FM gave mean differences of -0.010 and 0.137 ml/min per piece, respectively. All RM-FM differences, except those for scarlet FM, are within acceptable limits. This assay provides a reliable method for determining rCBF.

Validation of automated spectrofluroimetry for measurement of regional organ perfusion using fluorescent microspheres.

The fluorescent microsphere (FM) method for determination of regional organ blood flow is labor intensive, requiring processing of 100 s to 1000 s of samples per organ. To save time and reduce handling errors, we developed an automated fluorescence analysis system by interfacing a commercially available spectrofluorimeter and sample delivery unit to a PC, operated by a Windows95(R)-based program, WINFAC. WINFAC allows versatile analysis setup and instrument control for fluorescent intensity acquisition at fixed wavelengths or by synchronous scanning. Data is presented on screen, in real-time, and stored in text format. Reference analyses are performed at specified intervals and the coefficient of variation is continuously updated to monitor instrument performance. The automated system was validated against radioactive microspheres (RM) for lung perfusion in a pig and sheep and evaluated for analysis reproducibility. Fluorescent and radioactive microspheres were delivered by simultaneous injection into a femoral vein. Lungs were excised, flushed, dried at total lung capacity, and cubed into approximately 2cm(3) pieces (n=833 and 1560, pig and sheep, respectively). Radioactive count rates were determined for each lung piece (corrected for decay, background and spillover). Fluorescent dyes were extracted in solvent and intensities were determined at fixed wavelengths, using the automated spectrofluorimeter (corrected for background and spillover). Multi-color reference solutions were measured every 50 samples to monitor instrument reproducibility. Blood flow estimates for each piece determined by RM and FM methods were highly correlated: R(2)=0.98+/-0.017, Slopes=1.00+/-0.007 and Intercepts=0.00+/-0.006 (mean+/-SD). The CV of repeat reference analyses was 0.71%+/-0.16, a 30% to 50% reduction relative to manual analysis. Automated spectrofluorimetry reduces measurement errors and is a reliable and time saving advancement. With this technology, use of FM to measure regional lung perfusion approaches the ease and accuracy of the RM method.

Reading? ... pah! (I got it!). Innovative Reading Technique For Successful Deaf Readers.

A reading program utilizing five components--a shortcut to phonemic awareness, Adapted Dolch words, Bridge lists and the Bridging process, reading comprehension, and American Sign Language development/language experience stories--was administered to 48 elementary school students at a residential school for the deaf. Data analyses reveal dramatic gains in students' reading levels and academic behavior, teachers' growth in reflective sign skills, and students' and teachers' overall growth in ASL skills, resulting in a more organized, consistent approach to linguistic input and usage.

Extending fluorescent microsphere methods for regional organ blood flow to 13 simultaneous colors.

Seven fluorescent microsphere colors can be used in a single experiment to estimate regional blood flow without correcting for spillover of emitted fluorescence. To extend the method to 13 colors, we compared the accuracy of three methods for spillover correction. Fixed wavelength intensities were corrected by matrix inversion, and synchronous scan spectra were corrected by least squares fit of an overdetermined system of linear equations and by least squares fit of a sum of Gaussian and Lorentzian functions. Correction methods were validated in pigs and sheep by simultaneous injections of radioactive microspheres and fluorescent microspheres of 7, 10, and 13 different colors. We induced extreme changes in flow to create regions with low fluorescent signals bound on either side by high fluorescent signals. Blood flow was determined by radioactivity and by fluorescence using both fixed excitation and emission wavelength pairs and synchronous scanning and then corrected for spillover. Correlation between fluorescent intensity and radioactivity were excellent for all three correction methods [R2 = 0.98 +/- 0.02 (mean +/- SD)]. Low-flow regions requiring large spillover correction had systematic errors for some color combinations in all methods. We conclude that for 13 fluorescent colors spillover error can be minimized so that all three correction methods provide accurate estimates of regional blood flow.

Influence of fast-track anesthetic technique on cardiovascular infusions and weight gain.

OBJECTIVE: To evaluate whether cardiac surgical patients receiving conventional versus fast-track anesthetic management are statistically significantly different with regard to cardiovascular drug infusions, weight gain, cardiac and pulmonary morbidity, length of intubation, and length of stay. DESIGN: Retrospective, (partially) sequential, cohort design. SETTING: Surgical suite and intensive care unit (ICU) at a community hospital. PARTICIPANTS: Two hundred seven patients who presented for coronary artery bypass graft and/or cardiac valve replacement. INTERVENTIONS: None MEASUREMENTS AND MAIN RESULTS: Group comparisons of the seven individual cardiovascular drug infusions showed less frequent use in the fast-track patients for lidocaine (9% v 28%; p = 0.00046) only. However, the fast-track group received fewer combinations of cardiovascular drug infusions overall for the first 24-hour postoperative period (p < 0.0005). Hourly comparisons of inotropes showed significantly fewer combinations of dobutamine, norepinephrine, and epinephrine for the first postoperative hour and for postoperative hours 7 through 12 (p < 0.01 for each hour). Fast-track patients had less postoperative weight gain for days 1 through 4 (p < 0.01 for each day), shorter length of ICU stay (p < 0.00005), and shorter total length of postoperative hospital stay (p = 0.0004). No differences were found with respect to myocardial infarction, death, pulmonary complications, rate of reintubation, or length of hospital stay once discharged from the ICU. CONCLUSIONS: Fast-track anesthetic management may be associated with decreased need for inotropic and antiarrhythmic drug infusions and decreased weight gain.

Effects of vaporized perfluorocarbon on pulmonary blood flow and ventilation/perfusion distribution in a model of acute respiratory distress syndrome.

BACKGROUND: Perfluorocarbon (PFC) liquids are known to improve gas exchange and pulmonary function in various models of acute respiratory failure. Vaporization has been recently reported as a new method of delivering PFC to the lung. Our aim was to study the effect of PFC vapor on the ventilation/perfusion (VA/Q) matching and relative pulmonary blood flow (Qrel) distribution. METHODS: In nine sheep, lung injury was induced using oleic acid. Four sheep were treated with vaporized perfluorohexane (PFX) for 30 min, whereas the remaining sheep served as control animals. Vaporization was achieved using a modified isoflurane vaporizer. The animals were studied for 90 min after vaporization. VA/Q distributions were estimated using the multiple inert gas elimination technique. Change in Qrel distribution was assessed using fluorescent-labeled microspheres. RESULTS: Treatment with PFX vapor improved oxygenation significantly and led to significantly lower shunt values (P < 0.05, repeated-measures analysis of covariance). Analysis of the multiple inert gas elimination technique data showed that animals treated with PFX vapor demonstrated a higher VA/Q heterogeneity than the control animals (P < 0.05, repeated-measures analysis of covariance). Microsphere data showed a redistribution of Qrel attributable to oleic acid injury. Qrel shifted from areas that were initially high-flow to areas that were initially low-flow, with no difference in redistribution between the groups. After established injury, Qrel was redistributed to the nondependent lung areas in control animals, whereas Qrel distribution did not change in treatment animals. CONCLUSION: In oleic acid lung injury, treatment with PFX vapor improves gas exchange by increasing VA/Q heterogeneity in the whole lung without a significant change in gravitational gradient.

Spirometry and airway reactivity in elite track and field athletes.

OBJECTIVES: To characterize spirometry and to document the incidence of exercise-induced bronchospasm (EIB) during competition in elite track and field athletes. DESIGN: Spirometry was performed in 120 men and 69 women athletes before competition and peak expiratory flows in 50 men and 23 women athletes before and after competition. SETTING: The 1991 (Randalls Island, NY, U.S.A.) and the 1993 (Eugene, OR, U.S.A.) National Track and Field Championships (World Championship team-qualifying meet). PARTICIPANTS: American track and field athletes who met World Championship qualifying standards. MEASUREMENTS: Spirometry (Cybermedic, Inc., Boulder, CO, U.S.A.) and peak expiratory flows (Personal Best, Healthscan Products, Cedar Grove, NJ, U.S.A.)--the best of three reproducible efforts. RESULTS: Male sprinters had lower vital capacities than other track athletes, whereas both male and female field (throwing) athletes had larger vital capacities than both runners and other field athletes. Decreases of 10% peak expiratory flows were found in 10% of men and 26% of women track athletes within 15 min after competition. The incidence was higher in longer-distance events. Most participants did not have a history of asthma. CONCLUSIONS: A higher-than-expected prevalence of EIB was found in high-level track athletes. The results suggest that spirometry and/or peak flows should be measured in track athletes because small decreases in airflow may impair training or performance, a condition that is easily treated.