Spectroscopic data of pleural effusion

Pleural effusion is a medical condition having its etiology in various primary diseases, eg. cardiological, pulmonological, and oncological. It is a side effect of diseases such as pneumonia, tuberculosis, cancer, heart failure, and inflammation which are responsible for causing inflammatory diseases of the pleura. Late detection of pleural effusion disturbs the respiratory function, heart operation or may cause bleeding into the pleural cavity. In such a case, there is an immediate requirement for medical intervention and drainage of the pleural space or execution of pleurodesis causing pleural plaques to fuse, which is an invasive and potentially life-threatening procedure.
Therefore, patients with fluid in the pleural cavity, especially a group with recurrent pleural effusion should be continuously monitored.
In a standard clinical procedure, the presence of pleural effusion is diagnosed by a physician with the use of chest radiography, ultrasonography, or computed tomography. Although ultrasound becomes portable and handheld the diagnosis is possible only in the clinics or medical centers so far. The monitoring of pleural effusion in outpatients is still an unsolved problem.
So far, the use of near-infrared spectroscopy (NIRS) to test the amount of hydro-derivative fluids in various biomedical applications has been developed. For example, a method for assessing brain edema, water composition in rabbit meal, the water content in moisturizing creams or ceramic plasters has been published. In this work, the data form noninvasive NIRS measurement in patients with pleural effusion were collected. The method for noninvasive detection of pleural effusion using continuous-wave near-infrared spectroscopy is presented. The method has been developed based on numerical simulations of light transport in turbid media and validated on phantoms mimicking tissues and on patients with excess pleural fluid undergoing thoracocentesis.
Numerical simulations consisted in modeling light propagation in an optically turbid, non-homogeneous medium with tissue properties of peripulmonary structures and for various amounts of pleural fluid. A three-layer model depicting pleural effusion was adopted. It was assumed that the outer surface layer consists of skin, fat and muscle. Fiber optics were connected to this layer during measurements. Two fiber optics were used: one guiding the light from the source (emitter) and the second delivering to the spectrometer (detector). The second layer, present only when pleural effusion is present, is water layer. The third layer is the lung tissue layer. The NIRS measurement was performed in a reflective scenario.