Recently the authors have presented an unique solution for preventing clogging of microfluidic channels by gas bubbles [1]. It has been shown, that the bubble mobility can be enhanced, if two rectangular channels are nested in a T-shape. This geometrical configuration has been termed channel-in-channel (CHIC) design. In this paper the analytical approach introduced in [1] is enhanced and generalized. The extended approach, presented in this paper considers explicitly the two different equilibrium states of a gas bubble in dependence of the channel geometry and fluid parameters. The presented model allows the prediction of the bubble position and mobility. It is validated by experiments and it is demonstrated how it can be applied to optimise the channel geometry for a given cross section to achieve maximum bubble mobility.