We have worked closely with engineers at Laerdal Medical Corporation to develop a defibrillator that passively monitors the quality of CPR via additional external sensors (see details in the following reference: Abella BS, Alvarado JP, Myklebust H, Edelson DP, Barry A, O'Hearn N, Vanden Hoek TL, Becker LB. Quality of cardiopulmonary resuscitation during in-hospital cardiac arrest. JAMA. 2005;293:305-10).