[Routine bedside measurement of arterio-alveolar CO2 difference (author's transl)]

Deficiencies in pulmonary circulation can economically be demonstrated at the patient's bedside by measuring the difference in CO2 between arterial blood and alveolar air, which reflects the air flow in non-perfused ventilated lung areas. The method does not inform on the cause of the deficiency, but normal values (i.e. lower than 10 %) indicate that pulmonary circulation is unimpaired, whereas high values suggest that it is reduced (emboli, capillary obstruction by leukocytes). That the method is valid is shown by the parallelism observed between the percentage air flow in non-perfused ventilated areas and the angiographic and anatomical findings.