INTRODUCTION: A pneumatic tube system (PTS) is a cost-effective, rapid transport modality that utilizes induced pressure changes. We evaluated the clinical importance of 2 transport modalities, human courier and PTS, for blood gas specimens. METHODS: Following open heart surgery, 35 simultaneous pairs of arterial and venous blood gas specimens were analyzed from 20 subjects. Of each pair, one specimen was transported to the blood gas laboratory via a human courier and the other via a SwissLog PTS. Transport modalities were compared using the BlandAltman limits of agreement method. RESULTS: Compared with the walked specimen, the bias for P aCO 2 was ؊8.0 mm Hg (95% CI, ؊40.0 to 24.5 mm Hg); P aCO 2