Electroporation is usually described as a formation of transient pores in the cell membrane in the presence of a strong electric field, which enables transport of molecules and ions across the cell membrane. Several experimental studies of electroporation showed a complex dependence of the transport on pulse parameters. In only few studies, however, the actual transport across the membrane was quantified. Current theoretical studies can describe pore formation in artificial lipid membranes but still cannot explain mechanisms of formation and properties of long-lived pores which are formed during cell electroporation. The focus of our study is to connect theoretical description of pore formation during the electric pulses with experimental observation of increased transport after the pulses. By analyzing transient increase in conductivity during the pulses in parallel with ion efflux after the pulses the relation between short-lived and long-lived pores was investigated. We present a simple model that incorporates an increase in the fraction of long-lived pores with higher electric field due to larger area of the cell membrane exposed to above-critical voltage and due to higher energy which is available for pore formation. We also show that each consecutive pulse increases the probability for the formation of long-lived pores.