BACKGROUND The rheological properties of sputum may influence lung function and become modified in disease. OBJECTIVE This study aimed to correlate the viscoelastic properties of sputum with clinical data on the severity of disease in patients with chronic obstructive pulmonary disease (COPD). METHODS Sputum samples from COPD patients were investigated using rheology, simple mathematical modelling and Scanning Electron Microscopy (SEM). The samples were all collected from patients within two days of their admission to Prince Philip Hospital due to an exacerbation of their COPD. Oscillatory and creep rheological techniques were used to measure changes in viscoelastic properties at different frequencies over time. RESULTS COPD sputum was observed to behave as a viscoelastic solid at all frequencies studied. Comparing the rheology of exacerbated COPD sputum with healthy sputum (not diagnosed with a respiratory disease) revealed significant differences in response to oscillatory shear and creep-recovery experiments, which highlights the potential clinical benefits of better understanding sputum viscoelasticity. A common power law model G(t)=G0(tτ0)-m was successfully fitted to experimental rheology data over the range of frequencies studied. CONCLUSIONS A comparison between clinical data and the power law index m obtained from rheology, suggested that an important possible future application of this parameter is as a potential biomarker for COPD severity.

中文翻译：

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线性流变学作为慢性阻塞性肺疾病（COPD）患者痰液的潜在监测工具。

背景技术痰液的流变特性可能会影响肺功能并在疾病中发生改变。目的本研究旨在将痰的粘弹性与慢性阻塞性肺疾病（COPD）患者疾病严重程度的临床数据相关联。方法使用流变学，简单数学模型和扫描电子显微镜（SEM）对COPD患者的痰液样本进行调查。由于慢性阻塞性肺病的恶化，所有样本均在入院后两天内从患者那里收集。振荡和蠕变流变技术用于测量随时间变化的不同频率下粘弹性的变化。结果观察到COPD痰在所有研究频率下均表现为粘弹性固体。将慢性阻塞性肺病加重痰与健康痰（未确诊为呼吸系统疾病）的流变学进行比较，发现对振荡剪切和蠕变恢复实验的反应存在显着差异，这突显了更好地了解痰粘弹性的潜在临床益处。一个通用的幂律模型G（t）= G0（tτ0）-m已成功地拟合到所研究频率范围内的实验流变数据。结论从流变学获得的临床数据和幂律指数m之间的比较表明，该参数将来可能的重要应用是作为COPD严重程度的潜在生物标记。强调了更好地了解痰粘弹性的潜在临床益处。一个通用的幂律模型G（t）= G0（tτ0）-m已成功地拟合到所研究频率范围内的实验流变数据。结论从流变学获得的临床数据和幂律指数m之间的比较表明，该参数将来可能的重要应用是作为COPD严重程度的潜在生物标记。强调了更好地了解痰粘弹性的潜在临床益处。一个通用的幂律模型G（t）= G0（tτ0）-m已成功地拟合到所研究频率范围内的实验流变数据。结论从流变学获得的临床数据和幂律指数m之间的比较表明，该参数将来可能的重要应用是作为COPD严重程度的潜在生物标记。