The beating heart can be interpreted as an inborn natural oscillator generating mechanical energy. With the ventilated lung in close anatomical neighborhood the generated energy is partially transferred from the heart to the lung and further on propagated towards the airway opening inducing so called cardiogenic oscillations (CGO). During mechanical ventilation CGOs can be recognized as small fluctuations superimposed to the respiratory pattern applied by the respirator. We hypothesize that CGOs reflect the mechanical properties of the lung, especially changes in compliance. We analyzed 25 mechanically ventilated piglets during volume controlled ventilation, 13 of them healthy and 12 with pure oxygen produced initial atelectasis, at different PEEP levels (0, 5, 10 and 15 mbar). Compliances of the respiratory system (RS) were determined from CGO (CCGO) using first order polynomial fit and by SLICE method (CSLICE), both based on inspiratory pressure and flow signal. Resulting volume-compliance relationships of each method separately were utilized as supporting points for cubic spline interpolation. The resulting intratidal compliance tracks of both methods were compared to each other.