Frequency distribution of viscoelastic properties of sputum studied by the raised cosine pulse method: The effects of mucolytic agents 1

Abstract

We studies the frequency dependence of viscoelastic behavior of human sputum using our newly developed Raised Cosine Pulse (RCP) method. This method needs only 1.5 ml sputum, and allows us to estimate the responses of storage modulus ( ${\mathrm{G}}^{\prime }$ ) and loss modulus ( ${\mathrm{G}}^{″}$ ) to the change of angular frequency $\mathit{\omega }={10}^{-3}-{10}^0$ rad.sec⁻¹ in only 2–3 minutes by applying one small pulse strain. Measurements were made at 37°C and within 2 hours of expulsion. The results obtained by the RCP method and by a conventional method were compared and were roughly in agreement. From the behavior of ${\mathrm{G}}^{\prime }$ and ${\mathrm{G}}^{″}$ , the presence of a relaxation region at $\mathit{\omega }=3\times {10}^{-2}-3\times {10}^{-1}$ rad.sec⁻¹ could be deduced. The magnitude of relaxation increased and relaxation frequencies decreased, as the purulence of sputum increased. We also observed differences in viscoelastic behavior of sputum resulting from the application of mucolytic agents in vivo, which suggest corresponding changes of mechanical structures to the different pharmacological actions of these drugs.