Acoustic impedance method for detecting lung dysfunction.
NIOSH 1990 Sep; 1:312-316
This study's focus was to determine the differences in the acoustic impedance of excised silicotic and healthy rat lungs. Long-Evans- Hooded-rats were injected intratracheally with a silica (14808607) saline solution to induce silicosis. From 4 to 6 weeks following injection, all lungs were excised and degassed. The lungs were suspended in a pressure chamber, with the trachea canula attached to the end of a tapered impedance tube. The lungs were subjected to transpulmonary pressures between minus 30 to plus 6 centimeters (cm) water (H2O) to simulate deflation and inflation. The impedance tube was excited with random noise while the transpulmonary pressure was held constant. The transfer function between the two microphones was calculated and used to determine the lung's impedance at that pressure. Typical rats in both control and exposed groups had peaks at 2000, 3500, and 5500 hertz (Hz). Significant differences were noted between the silica and control groups at the peak of 3500Hz. The silica group had significantly higher impedance at transpulmonary pressures of 20 and 8cm of H2O during deflation. The silica group also had significantly higher impedance at 3500Hz at pressures of 6 and 4cm of H2O during deflation. These results indicated that changes in the mechanical properties of lung tissue and the closure of airways occurred at higher pressures in the silica group than in the control group. The authors conclude that silicosis in rat lungs can be detected by measuring the lung input impedance.
Laboratory-animals; Respiratory-system-disorders; Lung-tissue; Lung-irritants; Pulmonary-function; Airway-obstruction; Dust-exposure; Silica-dusts; In-vivo-study
DHHS (NIOSH) Publication No. 90-108; Grant-Number-G1135142
Proceedings of the VIIth International Pneumoconioses Conference