The Collaborative International Dictionary of English v.0.48:

Spirograph \Spi"ro*graph\, n. [L. spirare to breathe + -graph.]
   (Physiol.)
   An instrument for recording the respiratory movements, as the
   sphygmograph does those of the pulse.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spirograph
    n 1: a measuring instrument for recording the depth and rapidity
         of breathing movements