Heating-cooling effects on airway resistance measurement in rats.
Reynolds-JS; Frazer-DG; Stolarik-BM; McKinney-WG; Goldsmith-WT; Fedan-JS
Am J Respir Crit Care Med 1999 Mar; 159(3)(Suppl):A490
Effects of thermal artifacts due to heating/cooling of air on airway resistance-compliance (RawCg) measurements for rats by a two chamber plethysmograph have been studied. A simple RC model of the airways of a rat was coupled with an additional first order model of thermal flow. This system of equations is solved by a routine employing a Kalman gain for noise modeling. Four Sprague-Dawley rats were exposed to an aerosolized solution (15 mg/m3) of methacholine (300 mg/mL) for approximately six minutes. Measurements were taken pre- and post-exposure. RawCg and a thermal time constant (9) were found for inspiration and expiration. These were compared to RawCg calculated by a technique employed by Buxco using a double chamber plethysmograph which measures phase shift at the zero crossings after inspiration. Theta is smaller for inspiration because air heats faster during inspiration than it cools during expiration. The zero crossing method overestimates RawCg by not accounting for thermal effects. F or baseline measurements, RawCg is twice as large using the Buxco method but as RawCg increases relative to theta the error is less pronounced.
Analytical-processes; Analytical-methods; Airway-obstruction; Animal-studies; Animals; Laboratory-animals; Pulmonary-function-tests; Respiratory-function-tests; Alveolar-cells; Aerosol-particles; Airborne-dusts; Airborne-particles; Particulate-dust; Respiratory-system-disorders; Pulmonary-system-disorders; Exposure-assessment
Abstract; Conference/Symposia Proceedings
American Journal of Respiratory and Critical Care Medicine