Computer-assisted rheological evaluation of microsamples of mucus

Dynamic viscoelasticity measurements are required in many studies on biological fluids and they can be performed by determining the corresponding strain when a sinusoidal shear stress is applied to a sample. In several circumstances the amount of fluid that can be obtained for analysis in physiological conditions does not exceed microliters. In this context, the microrheometer technique is a useful approach to determine the dynamic rheological profile of the samples. However, the manual calculation of the desired parameters is tedious and time-consuming. This paper describes a menu-oriented program in order to facilitate its use by non-experts. The comparison between manual and computer-aided calculations demonstrated that the program reduced the time of measurement, and reduced intra- and interobserver variations. The program was developed on an IBM compatible PC in Microsoft C 5.1, and tested in a blind study to check the advantages in terms of time and reproducibility of the system verified by the concordance of two independent observers (interobserver influence) in two different occasions (intraobserver influence).