Red blood cell aggregation as measured with the LORCA.
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Coronary Artery Bypass↗
Biomedical subjects
J G G Dobbe
Publications and source records attributed to J G G Dobbe.
Validation and application of an automated rheoscope for measuring red blood cell deformability distributions in different species.
BACKGROUND: The deformability of red blood cells (RBCs) is of great importance for the conservation of oxygen delivery in the microcirculation. Even a small fraction of rigid cells is considered to harm the exchange of respiratory gases. Techniques that measure RBC deformability often provide an indication of the mean deformability. It may not be possible, however, to assess whether this mean value is reduced by the presence of a small rigid cell fraction or by a slight overall reduction in RBC deformability. A technique that provides a deformability distribution would be of great value to study diseases that are marked by subpopulations with a reduced deformability. METHODS: This paper describes a rheoscope system that uses advanced image analysis techniques to quickly quantify the deformability of many individual cells in shear flow, in order to find the RBC-deformability distribution. Since variations in the shear stress are responsible for variations in cell elongation, and hence introduce an additional spread in the cell deformability distribution, we first determined the spread caused by instrumental error. We then utilized the technique to investigate the relation between cell deformability and cell size of single blood samples of different species (human, pig, rat and rabbit). RESULTS: The spread caused by instrumental error was small compared to the actual RBC-deformability spread in blood samples. The deformability distribution of human and pig cells are alike although their cell sizes are different. Rat and rabbit cells show comparable deformability and size distributions. With this technique no correlation was found between cell deformability and cell size in animal RBCs. In the human sample a minor correlation was found between cell deformability and cell size. CONCLUSIONS: The automated rheoscope enables us to study the mechanical properties of RBCs more thoroughly by their deformability distribution. These deformability distributions are hardly influenced by the technique or by cell size.
Animals↗
Measurement of the distribution of red blood cell deformability using an automated rheoscope.
BACKGROUND: Red blood cells (RBCs) have to deform markedly to pass through the smallest capillaries of the microcirculation. Techniques for measuring RBC deformability often result in an indication of the mean value. A deformability distribution would be more useful for studying diseases that are marked by subpopulations of less deformable cells because even small fractions of rigid cells can cause circulatory problems. METHODS: We present an automated rheoscope that uses advanced image analysis techniques to determine a RBC deformability distribution (RBC-DD) by analyzing a large number of individual cells in shear flow. The sensitivity was measured from density-separated fractions of one blood sample and from cells rendered less deformable by heat treatment. A preliminary experiment included the RBC-DDs of a patient with sickle cell anemia, one on dialysis and being treated with erythropoietin, and one with elliptocytosis. RESULTS: Measurement of the RBC-DD was highly reproducible. The sensitivity test showed markedly different deformability distributions of density-separated cells and yielded distinct RBC-DDs after each additional minute of heat treatment. CONCLUSION: The automated rheoscope enabled the determination of RBC-DDs from which less deformable subpopulations can be established. The shape of an RBC-DD may be valuable in assessing cell fractions with normal and anomalous deformability within pathologic blood samples.
Erythrocyte Deformability↗
Analyzing red blood cell-deformability distributions.
BACKGROUND: Red blood cells (RBCs) must deform to pass the smallest capillaries of the microcirculation. Available techniques for measuring RBC deformability often provide an indication of the mean deformability. The latter may be decreased either by a slight overall deformability reduction or by the presence of a small fraction of rigid cells. A distinction between these two cases can be made with a RBC-deformability distribution (RBC-DD). METHODS: This paper explores RBC-DDs of healthy individuals and of cells with anomalous mechanical properties (sickle cell disease, dialysis patients, elliptocytosis, and cultivated malaria tropica). The distributions were measured with an automated rheoscope, which uses advanced image analysis techniques to obtain the deformability index of a large number of individual cells subjected to simple shear flow. RESULTS: The RBC-DD of healthy volunteers is close to a normal distribution. In the investigated patients, distributions were markedly different and yielded significant changes in the mean, in the standard deviation, or in both. The presence of hypodeformable and hyperdeformable cell fractions can qualitatively and quantitatively be assessed from the deformability distribution (DD). In elliptocytosis, cells orient differently with respect to the streamlines, compared to normal cells. This causes the DD to be biased. CONCLUSIONS: The RBC-DD is a powerful representation to establish subpopulations with anomalous deformability. Fractions of hypodeformable and hyperdeformable cells and the standard deviation of the DD are new and excellent quantitative parameters to assess alterations in RBC deformability.
Anemia, Sickle Cell↗
Patient compliance with a rehabilitation program after flexor tendon repair in zone II of the hand.
The use of early mobilization during rehabilitation of a finger after flexor tendon repair in zone II has achieved worldwide acceptance. Different exercise instructions are given to patients in different clinics, however. When using Kleinert dynamic splinting, some hand therapists instruct patients to exercise 10 times an hour, while others tell their patients to exercise as many times as possible. How often a patient should exercise to achieve optimal results has never, to the authors' knowledge, been investigated. To identify a relationship between exercise behavior and range of motion achieved at 6 months postoperatively, the authors started a pilot study of the compliance of 15 patients with a rehabilitation program following flexor tendon repair in zone II. A portable rehabilitation device was used to deliver an isotonic tensile force and to record when (during the day) a patient exercises and how many exercises the patient performs. Patients were instructed to perform at least ten exercises per hour. The average count per hour was 69 exercises (range, 14-213). In this small group study, no strong correlation was found between exercise count and the total active or total passive motion achieved.
Adult↗