OBJECTIVETo observe temperature and pressure changes inside plethysmograph produced by body temperature of anesthetized mice.

METHODSThe temperature and pressure changes inside whole body plethysmograph generated from anesthetized mice were compared with those from dead mice. The temperature and pressure changes inside body chamber and head chamber of double-chamber with anesthetized mice in body chamber were synchronously measured. The respiratory frequencies and amplitudes of mice inside two kinds of head-out plethysmographs were synchronously measured. One of these two plethysmographs kept sealed all the time and the other was opened to the atmosphere for 1 min every 2 min.

RESULTTemperature and pressure of air in the anesthetized mice chamber increased 1.18 degree and 2.710 mmHg within 6 min, and data from dead mice were 1.17 degree and 2.671 mmHg. There were no significant differences between these two groups. The temperature inside body chamber increased 1.92 degree in 20 min and the pressure was 5.554 mmHg, which were significantly higher than those of head chamber (0.09 degree and 0.627 mmHg). The respiratory frequencies of mice in the sealed head-out plethysmograph increased from 125.04 per min to 168.45 per min, and amplitudes of pressure changes generated from mice breath decreased from 1.090 mmHg to 0.883 mmHg. Significant differences occurred between different observation time points. Meanwhile respiratory frequencies in the open head-out plethysmograph were around 120 per min and amplitude of pressure changes kept about 1 mmHg. There were no significant differences between different time points.

CONCLUSIONIncrease of temperature and pressure inside pressure whole-body plethysmograph are mainly from body temperature of mice, and the increased pressure significantly influences respiration of mice.