There has recently been an increased attention focused on the importance of reducing time without blood flow from chest compressions (no flow time, NFT) during cardiopulmonary resuscitation (CPR). In this study we have analyzed and quantified the NFTs during external automatic defibrillation in 105 cardiac arrest patients. We found that for around half of the time (about 10 min), these patients were not perfused. We have proposed methods to reduce NFT in connection with analyses and shocks. The key factors were rhythm analysis during ongoing CPR, capacitor charging during analysis, 1 min of CPR immediately after a shock (with rhythm analysis during CPR at the end of the 1 min), and distinguishing between asystole and organized rhythm in analyses to skip pulse check if asystole. The potential reduction in NFT using these methods was calculated theoretically and we found a reduction in the total NFT of about 4.5 and 1 min, respectively, in the subgroups of patients having at least one shock and patients having received no shocks. In the present study, the median NFT ratio could theoretically be reduced from 51% to 34% or 49% to 39% depending on if the patient would have a shockable rhythm or not. By introducing the proposed methods into an AED, the NFT would be significantly reduced, hopefully increasing the survival.