Optical measurement of isolated canine lung filtration coefficients at normal hematocrits

Klaesner, Joseph W., N. Adrienne Pou, Richard E. Parker,Charlene Finney, and Robert J. Roselli. Optical measurement ofisolated canine lung filtration coefficients at normal hematocrits. J. Appl. Physiol. 83(6):1976-1985, 1997.In this study, lung filtration coefficient(K_fc) valueswere measured in eight isolated canine lung preparations at normalhematocrit values using three methods: gravimetric, blood-correctedgravimetric, and optical. The lungs were kept in zone 3 conditions andsubjected to an average venous pressure increase of 10.24 ± 0.27 (SE) cmH₂O. The resulting K_fc(ml · min¹ · cmH₂O¹ · 100 g dry lung wt¹) measuredwith the gravimetric technique was 0.420 ± 0.017, which wasstatistically different from theK_fc measured bythe blood-corrected gravimetric method (0.273 ± 0.018) or theproduct of the reflection coefficient(_f) andK_fc measuredoptically (0.272 ± 0.018). The optical method involved the use of aCellco filter cartridge to separate red blood cells from plasma, whichallowed measurement of the concentration of the tracer in plasma atnormal hematocrits (34 ± 1.5). The permeability-surface areaproduct was measured using radioactive multiple indicator-dilutionmethods before, during, and after venous pressure elevations. Resultsshowed that the surface area of the lung did not change significantlyduring the measurement ofK_fc. Thesestudies suggest that_fK_fccan be measured optically at normal hematocrits, that this measurement is not influenced by blood volume changes that occur during the measurement, and that the optical_fK_fcagrees with theK_fc obtained viathe blood-corrected gravimetric method.

     

Optical measurement of isolated canine lung filtration coefficients after alloxan infusion

In this study, lung filtration coefficient(K_fc) wasmeasured in eight isolated canine lung preparations by using threemethods: standard gravimetric (Std), blood-corrected gravimetric (BC), and optical. The lungs were held in zone III conditions and were subjected to an average venous pressure increase of 8.79 ± 0.93 (mean ± SD) cmH₂O. Thepermeability of the lungs was increased with an infusion of alloxan (75 mg/kg). The resultingK_fc values (inmilliliters · min¹ · cmH₂O¹ · 100 g dry lung weight¹)measured by using Std and BC gravimetric techniques before vs. afteralloxan infusion were statistically different: Std, 0.527 ± 0.290 vs. 1.966 ± 0.283; BC, 0.313 ± 0.290 vs. 1.384 ± 0.290. However, the optical technique did not show any statisticaldifference between pre- and postinjury with alloxan, 0.280 ± 0.305 vs. 0.483 ± 0.297, respectively. The alloxan injury, quantified byusing multiple-indicator techniques, showed an increase in permeability and a corresponding decrease in reflection coefficient for albumin (_f). Because the opticalmethod measures the product ofK_fc and _f, this study shows thatalbumin should not be used as an intravascular optical filtrationmarker when permeability is elevated. However, the optical technique,along with another means of measuringK_fc (such as BC),can be used to calculate the _fof a tracer (in this study, _fof 0.894 at baseline and 0.348 after injury). Another important findingof this study was that the ratio of baseline-to-injury K_fc values wasnot statistically different for Std and BC techniques, indicating thatthe percent contribution of slow blood-volume increases does not changebecause of injury.

     

An Accelerometry-Based Methodology for Assessment of Real-World Bilateral Upper Extremity Activity

Background

The use of both upper extremities (UE) is necessary for the completion of many everyday tasks. Few clinical assessments measure the abilities of the UEs to work together; rather, they assess unilateral function and compare it between affected and unaffected UEs. Furthermore, clinical assessments are unable to measure function that occurs in the real-world, outside the clinic. This study examines the validity of an innovative approach to assess real-world bilateral UE activity using accelerometry.

Methods

Seventy-four neurologically intact adults completed ten tasks (donning/doffing shoes, grooming, stacking boxes, cutting playdough, folding towels, writing, unilateral sorting, bilateral sorting, unilateral typing, and bilateral typing) while wearing accelerometers on both wrists. Two variables, the Bilateral Magnitude and Magnitude Ratio, were derived from accelerometry data to distinguish between high- and low-intensity tasks, and between bilateral and unilateral tasks. Estimated energy expenditure and time spent in simultaneous UE activity for each task were also calculated.

Results

The Bilateral Magnitude distinguished between high- and low-intensity tasks, and the Magnitude Ratio distinguished between unilateral and bilateral UE tasks. The Bilateral Magnitude was strongly correlated with estimated energy expenditure (ρ = 0.74, p<0.02), and the Magnitude Ratio was strongly correlated with time spent in simultaneous UE activity (ρ = 0.93, p<0.01) across tasks.

Conclusions

These results demonstrate face validity and construct validity of this methodology to quantify bilateral UE activity during the performance of everyday tasks performed in a laboratory setting, and can now be used to assess bilateral UE activity in real-world environments.