Fast integrated flow plethysmograph for small mammals.
The accurate measurement of a forced vital capacity (FVC) maneuver in a small mammal requires that the plethysmograph in use have good response characteristics at high frequencies. We develop, on a theoretical basis, the behavior of zeroth-order (pressure type), first-order (flow type without inertance), and second-order (flow type with inertance) plethysmogrphs. The actual frequency response of a mouse-sized plethysmograph is then presented, and a technique for improving its response characteristics is described. A flat amplitude response (within 3% of a reference flow taken as truth) was obtained for sinusoidal inputs below 240 Hz. A phase lag with respect to the reference flow equivalent to a simple time delay of 1.4 ms was observed up to 150 Hz. A typical FVC curve for a mouse is shown, and criteria are provided for designing similar plethysmographs suitable for use with larger animals.
D000818:Animals; D006224:Cricetinae; D005540:Forced Expiratory Flow Rates; D006168:Guinea Pigs; D008449:Maximal Expiratory Flow-Volume Curves; D051379:Mice; D010992:Plethysmography, Impedance / Q000295:instrumentation*; D051381:Rats; D014797:Vital Capacity