Medicament delivery system and method therefor

A medicament delivery system comprising:

• a cassette comprising a medicament bag in an interior thereof;
• and
• a pump unit separable from the cassette, wherein an air flow connection is provided between the pump unit and the interior of the cassette,
• wherein the pump unit comprises a pump and an air valve,
• wherein the pump is configured to pressurise the interior of the cassette to exert a pressure on the medicament bag, and
• wherein the air valve is configured to de-pressurise the cassette by releasing the pressure from the interior of the cassette,
• wherein the pump unit comprises a processing unit and wherein the processing unit is configured to control the pump and the air valve to periodically pressurise and de-pressurise the interior of the cassette,
• wherein the processing unit is configured to perform the periodic pressurising and de-pressurising based on a difference of the ambient air temperature and the temperature of the interior of the cassette.