ULTRASONIC MEASUREMENTS OF BREATHING RATE IN RATS AND COMPUTER-ASSISTED ANALYSIS

Purpose: An ultrasound breathing rate measurement technique and a comp uter analysis algorithm have been developed to reduce the amount of ti me needed to collect and analyze animal breathing rate data, as well a s to improve the testing environment. The system is not airtight, ther efore, acclimatization and collection time is not limited, and the tec hnique makes use of a top loading apparatus to facilitate animal entry . Methods and Materials: Breathing rate is measured using two ultrasou nd transducers housed directly above the rat thorax in the plexiglass jig. The breathing rate signal is stored and evaluated by computer. Th e ultrasound technique was tested using a loud speaker driven by a sig nal generator, over a range of 30 to 450 cycles/min. In addition, the ultrasonic breathing rate method was used to record the breathing rate response of Sprague Dawley rats, treated with graded single doses of radiation, over a period of 170 days. Results: For the loud speaker te sts, the measured frequency agreed with that of the input signal with a maximum deviation of 1%. For the animal irradiations, all breathing rate data were analyzed by both user and computer selection of regular breathing. The techniques gave the same results at the 95% confidence limit. Using the computer program to assess the traces, 240 breathing rates can be determined per hour, from previously measured data. Conc lusion: A new technique for measuring breathing rate has been develope d and enhances both the collection and analysis of data.