  Asthma is becoming a very serious problem with every passing day, especially
in children. However, it is very difficult to detect this disorder in them,
since the breathing motion of children tends to change when they reach an age
of 6. This, thus makes it very difficult to monitor their respiratory state
easily. In this paper, we present a cheap non-contact alternative to the
current methods that are available. This is using a stereo camera, that
captures a video of the patient breathing at a frame rate of 30Hz. For further
processing, the captured video has to be rectified and converted into a point
cloud. The obtained point clouds need to be aligned in order to have the output
with respect to a common plane. They are then converted into a surface mesh.
The depth is further estimated by subtracting every point cloud from the
reference point cloud (the first frame). The output data, however, when plotted
with respect to real time produces a very noisy plot. This is filtered by
determining the signal frequency by taking the Fast Fourier Transform of the
breathing signal. The system was tested under 4 different breathing conditions:
deep, shallow and normal breathing and while coughing. On its success, it was
tested with mixed breathing (combination of normal and shallow breathing) and
was lastly compared with the output of the expensive 3dMD system. The
comparison showed that using the stereo camera, we can reach to similar
sensitivity for respiratory motion observation. The experimental results show
that, the proposed method provides a major step towards development of low-cost
home-based observation systems for asthma patients and care-givers.
