An optical imaging system for use with an infusion tube having a drip chamber and an output tube. The drip chamber includes a first portion with a drip tube, a second portion with an exit port, and a third portion between the first and second portions. The optical imaging system includes: an illumination system with at least one light source for emitting light, an optical system, and a memory element storing computer executable instructions. The optical system receives the light transmitted by the output tube or the second portion and transmits data characterizing the received light. The system includes at least one processor configured to execute the computer executable instructions to: detect, using the data, an air bubble in the output tube or the second portion; and determine a volume of the detected air bubble.