HFOV (High frequency oscillatory ventilation) is an effective artificial respiration technique for the treatment of pulmonary disease patients. In HFOV, the pendelluft is one of the important factors in gas transport and mixing mechanisms. Experimental analysis of the pendelluft flow generated in a bronchial tube model of single bifurcation with different volume ratios of daughter branches has been carried out by using time-resolved micro-particle image velocimetry obtaining instantaneous velocity distributions of oscillatory flows in the bronchial tube model at a frequency range of 10-15 Hz. Based on the oscillatory velocity profiles changing with time for different frequencies, the pendelluft phenomena have been discussed.