Red cell distortion and conceptual basis of diffusing capacity estimates: finite element analysis |
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Authors: | Hsia C CW; Chuong C JC; Johnson R L Jr |
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Abstract: | Hsia, C. C. W., C. J. C. Chuong, and R. L. Johnson, Jr.Red cell distortion and conceptual basis of diffusing capacity estimates: finite element analysis. J. Appl.Physiol. 83(4): 1397-1404, 1997. To understandthe effects of dynamic shape distortion of red blood cells (RBCs) as itdevelops under high-flow conditions on the standard physiological andmorphometric methods of estimating pulmonary diffusing capacity, wecomputed the uptake of CO across a two-dimensional geometric capillarymodel containing a variable number of equally spaced RBCs. RBCs arecircular or parachute shaped, with the same perimeter length. Total COdiffusing capacity (DLCO)and membrane diffusing capacity(DMCO)were calculated by a finite element method.DLCOcalculated at two levels of alveolar PO2 were used to estimateDMCO by theRoughton-Forster (RF) technique. The same capillary model was subjectedto morphometric analysis by the random linear intercept method toobtain morphometric estimates ofDMCO. Results show thatshape distortion of RBCs significantly reduces capillary diffusive gasuptake. Shape distortion exaggerates the conceptual errors inherent inthe RF technique (J. Appl. Physiol.79: 1039-1047, 1995); errors are exaggerated at a high capillaryhematocrit. Shape distortion also introduces additional error inmorphometric estimates ofDMCO causedby a biased sampling distribution of random linear intercepts; errors are exaggerated at a low capillary hematocrit. |
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