A cartridge and system involving a joint spectroscopic and biosensor blood analyzer for measurement of at least two hemoglobin species in a patient's blood sample by spectroscopy, and measurement of at least pH of the blood sample by biosensor, for assessing the patient's oxygenation and acid-base status. The cartridge comprises a housing having a first housing member and a second housing member bonded together by a gasket. The housing comprises a cartridge inlet； a blood storage conduit； an optical chamber； a biosensor conduit； a waste receptacle； a vent； an air bladder, an air bladder exit port； and, an optical window and an aligned optical member, the aligned optical member being one of a reflecting member or a second optical window, and being positioned to align with at least a portion of the optical chamber and at least a portion of the optical window.
