A catheter positioning system comprising: a processor; and non-transitory computer readable medium in communication with the processor with instructions thereon, that when executed by the processor, cause the processor to: apply a first electrical current signal between one or more electroconductive body surface patches and a probe electrode, the electroconductive body surface patches being configured for electrical conductivity through skin of a patient, and the probe electrode being affixed to a distal expandable member of a catheter configured for insertion into the patient's body, measure a first electrical voltage signal between at least one of the one or more electroconductive body surface patches and probe electrode, the first electrical voltage signal resulting from the applied first electrical current signal, determine, based at least in part on the first electrical voltage signal, a length of the distal expandable member, compare the length to a longitudinal threshold value, provide an output indicating a change in shape of the distal expandable member when the length crosses the longitudinal threshold value, and (i) compare the length to a minimum re-sheathing length, and when the length increases to exceed the minimum re-sheathing length, trigger low flow to the distal expandable member and prevent high flow being activated to inflate the distal expandable member, or: (ii) when the length decreases to below the longitudinal threshold value, allow high flow to inflate the distal expandable member. a processor; and non-transitory computer readable medium in communication with the processor with instructions thereon, that when executed by the processor, cause the processor to: apply a first electrical current signal between one or more electroconductive body surface patches and a probe electrode, the electroconductive body surface patches being configured for electrical conductivity through skin of a patient, and the probe electrode being affixed to a distal expandable member of a catheter configured for insertion into the patient's body, measure a first electrical voltage signal between at least one of the one or more electroconductive body surface patches and probe electrode, the first electrical voltage signal resulting from the applied first electrical current signal, determine, based at least in part on the first electrical voltage signal, a length of the distal expandable member, apply a first electrical current signal between one or more electroconductive body surface patches and a probe electrode, the electroconductive body surface patches being configured for electrical conductivity through skin of a patient, and the probe electrode being affixed to a distal expandable member of a catheter configured for insertion into the patient's body, measure a first electrical voltage signal between at least one of the one or more electroconductive body surface patches and probe electrode, the first electrical voltage signal resulting from the applied first electrical current signal, determine, based at least in part on the first electrical voltage signal, a length of the distal expandable member, compare the length to a longitudinal threshold value, provide an output indicating a change in shape of the distal expandable member when the length crosses the longitudinal threshold value, and (i) compare the length to a minimum re-sheathing length, and when the length increases to exceed the minimum re-sheathing length, trigger low flow to the distal expandable member and prevent high flow being activated to inflate the distal expandable member, or: (ii) when the length decreases to below the longitudinal threshold value, allow high flow to inflate the distal expandable member. (i) compare the length to a minimum re-sheathing length, and when the length increases to exceed the minimum re-sheathing length, trigger low flow to the distal expandable member and prevent high flow being activated to inflate the distal expandable member, or: (ii) when the length decreases to below the longitudinal threshold value, allow high flow to inflate the distal expandable member.