A flow-through pressure spike absorbing system for intravenous therapy tubing (110, 112), comprising: a housing comprising a cavity, a ventilation passage that extends from the cavity to an outer surface of the housing, a first retaining bore, a first tubing passage, a second retaining bore, and a second tubing passage, wherein the first retaining bore extends from the cavity toward a first portion of the housing, and the first tubing passage extends through the first portion of the housing, from the first retaining bore to the outer surface of the housing, and wherein the second retaining bore extends from the cavity toward a second portion of the housing, and the second tubing passage extends through the second portion of the housing, from the second retaining bore to the outer surface of the housing; an expandable reservoir comprising a first portion having a first opening, a second portion having a second opening, and an inner surface forming a passage that extends between the first and second openings (302, 304), wherein the expandable reservoir is positioned within the cavity with the first portion of the expandable reservoir within the first retaining bore such that a first tubing can be inserted into the first opening to be coupled to the expandable reservoir and with the second portion of the expandable reservoir within the second retaining bore such that a second tubing can be inserted into the second opening to be coupled to the expandable reservoir wherein, when a fluid is injected through the first tubing, the fluid is directed into the passage to move the expandable reservoir from an unrestrained orientation toward an expanded orientation, and wherein the ventilation passage is configured to permit a gas to move out of the cavity when the expandable reservoir moves from the unrestrained orientation toward the expanded orientation, and to permit a gas to move into the cavity when the expandable reservoir moves from the expanded orientation toward the unrestrained orientation. a housing comprising a cavity, a ventilation passage that extends from the cavity to an outer surface of the housing, a first retaining bore, a first tubing passage, a second retaining bore, and a second tubing passage, wherein the first retaining bore extends from the cavity toward a first portion of the housing, and the first tubing passage extends through the first portion of the housing, from the first retaining bore to the outer surface of the housing, and wherein the second retaining bore extends from the cavity toward a second portion of the housing, and the second tubing passage extends through the second portion of the housing, from the second retaining bore to the outer surface of the housing; an expandable reservoir comprising a first portion having a first opening, a second portion having a second opening, and an inner surface forming a passage that extends between the first and second openings (302, 304), wherein the expandable reservoir is positioned within the cavity with the first portion of the expandable reservoir within the first retaining bore such that a first tubing can be inserted into the first opening to be coupled to the expandable reservoir and with the second portion of the expandable reservoir within the second retaining bore such that a second tubing can be inserted into the second opening to be coupled to the expandable reservoir wherein, when a fluid is injected through the first tubing, the fluid is directed into the passage to move the expandable reservoir from an unrestrained orientation toward an expanded orientation, and wherein the ventilation passage is configured to permit a gas to move out of the cavity when the expandable reservoir moves from the unrestrained orientation toward the expanded orientation, and to permit a gas to move into the cavity when the expandable reservoir moves from the expanded orientation toward the unrestrained orientation.