A method for determining whether an organ is suitable for transplant comprising: providing a mobile perfusion apparatus comprising: a pumping chamber comprising a first portion and a second portion; a tissue chamber defined by a canister and a bottom portion of the pumping chamber; a semi-permeable membrane disposed between the first portion and the second portion, the membrane having an upper surface and a lower surface, the upper surface in contact with an oxygen-containing gas and the lower surface in contact with a preservation solution, wherein the membrane is configured to allow[[s]] oxygen from the oxygen containing gas to pass through the membrane and into the preservation solution while a pressure provided against the membrane by the oxygen-containing gas exerts a force against the preservation solution; and a fill port defining a lumen having a first opening and a second opening, wherein the first opening opens to the exterior of the tissue chamber and the second opening opens to the tissue chamber; placing an organ into the tissue chamber; pumping preservation solution through a fill port to purge trapped gas from the tissue chamber; pumping oxygen through the apparatus to perfuse the organ disposed within the preservation solution with the oxygenated solution; varying the pressure of the oxygen-containing gas at least once per minute, thereby causing a time-dependent pressure change in the preservation solution perfusing the organ; measuring an oxygen consumption rate of the organ with an oxygen sensor; and comparing the measured oxygen consumption rate to a functional oxygen consumption rate, wherein a measured oxygen consumption rate greater than or equal to the functional oxygen consumption rate indicates that the organ is suitable for transplant. providing a mobile perfusion apparatus comprising: a pumping chamber comprising a first portion and a second portion; a tissue chamber defined by a canister and a bottom portion of the pumping chamber; a semi-permeable membrane disposed between the first portion and the second portion, the membrane having an upper surface and a lower surface, the upper surface in contact with an oxygen-containing gas and the lower surface in contact with a preservation solution, wherein the membrane is configured to allow[[s]] oxygen from the oxygen containing gas to pass through the membrane and into the preservation solution while a pressure provided against the membrane by the oxygen-containing gas exerts a force against the preservation solution; and a fill port defining a lumen having a first opening and a second opening, wherein the first opening opens to the exterior of the tissue chamber and the second opening opens to the tissue chamber; a pumping chamber comprising a first portion and a second portion; a tissue chamber defined by a canister and a bottom portion of the pumping chamber; a semi-permeable membrane disposed between the first portion and the second portion, the membrane having an upper surface and a lower surface, the upper surface in contact with an oxygen-containing gas and the lower surface in contact with a preservation solution, wherein the membrane is configured to allow[[s]] oxygen from the oxygen containing gas to pass through the membrane and into the preservation solution while a pressure provided against the membrane by the oxygen-containing gas exerts a force against the preservation solution; and a fill port defining a lumen having a first opening and a second opening, wherein the first opening opens to the exterior of the tissue chamber and the second opening opens to the tissue chamber; placing an organ into the tissue chamber; pumping preservation solution through a fill port to purge trapped gas from the tissue chamber; pumping oxygen through the apparatus to perfuse the organ disposed within the preservation solution with the oxygenated solution; varying the pressure of the oxygen-containing gas at least once per minute, thereby causing a time-dependent pressure change in the preservation solution perfusing the organ; measuring an oxygen consumption rate of the organ with an oxygen sensor; and comparing the measured oxygen consumption rate to a functional oxygen consumption rate, wherein a measured oxygen consumption rate greater than or equal to the functional oxygen consumption rate indicates that the organ is suitable for transplant.