Repetitive measurements of enhanced pause (Penh)

• Penh values are different at different time points.
• Penh may not be closely related to airway resistance.
• Penh is not an ideal index for long time measurement.

Enhanced pause (Penh) was first proposed in allergic mice and appeared to be correlated with airway responsiveness. However, some investigators have suggested that there is no theoretical basis for a correlation between Penh and airway resistance. Because the measurement of Penh is a noninvasive procedure, this value may be useful in repetitive measurements, but few researchers have emphasized this aspect. This study aimed to assess the validity of Penh values derived through repetitive measurements of both absolute and ratio Penh values in 10 male C57BL/6 mice on days 0, 3, 7, and 15. Tests of within-subject effects revealed significant differences in both the absolute and ratio Penh values across the different time points. The administration of challenge aerosolized methacholine concentrations of 25, 50, and 100 mg/ml resulted in significant differences in the ratio Penh values across the various time points. The findings of the present study indicate that Penh is not a good index for repetitive measurement because the Penh values are significantly influenced by the time at which they are measured.