receiving a chest X-ray image of a patient;

detecting rib bones in the chest X-ray image;

identifying a plurality of intercostal spaces each representing a space between adjacent detected rib bones;

detecting a diaphragm in the chest X-ray image and generating a diaphragm line comprising a plurality of points representing a path of a diaphragm in the chest X-ray image;

assigning a point score to each point of the diaphragm line using a score assigning rule, wherein the score assigning rule defines a correspondence in the image between a point of the diaphragm line and an intercoastal space; and

determining an inhalation index based on the point scores of the points of the diaphragm line.