1. An image analysis device comprising: an acquiring unit configured to acquire a moving image showing a variation of a respiratory status, the moving image being formed with frame images comprising an image of a heart; an image analyzing unit that receives the moving image from the acquiring unit, wherein the image analyzing unit is configured to generate from the moving image a first index indicating a cardiac status with respect to each of the frame images, wherein each of the first indexes is one of a heart size, and a pixel value of a region in which the heart is depicted; and an index analyzing unit that receives the first indexes for each of the frame images, wherein the index analyzing unit is configured to derive a second index indicating lung function from a change caused in the first indexes of the frame images by the respiratory status.