This study has been conducted in compliance with the Animal Research Committee, Hamamatsu University School of Medicine, and the principles of the Guide for the Care and Use of Laboratory Animals: 8-week-old ICR female mice, weighing 29 to 31 g, were obtained from Japan SLC Inc. (Hamamatsu, Japan) for this study. They were housed individually in a specific pathogen-free facility. The hair on the forehead of the mice was cut short to decrease the influence of hair in oximetry measurement. At first, every mouse was measured at the craniofacial site by the oximetry at 21% of oxygen concentration (indoor oxygen content) and in the range of 24.0°C to 24.5°C. One mouse was placed in a cage (CL-0113-4; width 136 mm, depth 208 mm, height 115 mm, CLEA Japan Inc., Tokyo, Japan), with some blocks of dry ice (solidified carbon dioxide), and an oxygen concentration meter (XP-3180E, New Cosmos Electric Co., Ltd., Osaka, Japan) was enclosed in a polyethylene bag (width 65 cm and depth 80 cm). Examiners detected the decrease in the oxygen concentration and measured the and total hemoglobin index (T-HbI) at the craniofacial site in the polyethylene bag, preventing the entry of any outside air as much as possible. After a mouse was measured one to four times in the polyethylene bag, examiners immediately cut the facial vessel using a lancet and collected the blood using a capillary tube (at least three drops). Immediately after blood collection, a sample for pH measurement was evaluated using the handheld i-STAT®1 Analyzer (Abbot Laboratories, East Windsor, New Jersey) and EG6+ cartridge (Abbott Laboratories, East Windsor, New Jersey). Examiners did not investigate the and T-HbI using oximetry again once the blood sample was collected. The value of the and T-HbI was investigated three times until the numeric data stabilized. A median value from all the measurement data was selected as a numeric value for the data under the conditions of oxygen concentration. Statistical significance was calculated using a Spearman’s correlation coefficient. A value of was considered statistically significant.