Validation of a portable blood gas analyzer for use in challenging field conditions

Introduction: Portable arterial blood gas analyzers (pABGA) may serve as essential diagnostic tools in remote regions, during air travel, in ambulance services or room-shared space-limited outpatient clinics but they have not been extensively validated. Methods: Accuracy of the battery driven pABGA EPOC (Siemens Healthcare GmbH, Zurich, Switzerland) was compared to a validated stationary ABGA (Rapidpoint500, Siemens). In healthy individuals and patients with chronic obstructive pulmonary disease who participated in trials of acetazolamide for prevention of altitude illness, arterial blood samples were obtained and analyzed by EPOC and Rapidpoint500. Bias (mean difference) and limits of agreement (95% CI of bias) in paired measurements were computed. Results: In 105 individuals, 108 arterial blood samples were obtained at 760m and 140 at 3’100m. Ranges of values measured by EPOC were: pH 7.241 to 7.473, PaCO2 2.87 to 7.00kPa, PaO2 6.1 to 14.3kPa. Bias (95%CI) between EPOC and RP500 were: pH 0.007 (-0.029 to 0.044), PaCO2 -0.04kPa(-0.64 to 0.56) and PaO2 -0.29kPa(-1.21 to 0.62). A trend for overestimation of pH by EPOC in the low and underestimation in the high range could be corrected by the equation pH_RP500= -1.37+pH_EPOC*1.19 (R2=0.906), corrected bias -0.007 (-0.023 to 0.009). Handling of EPOC was easy and the device worked reliably. Conclusions: The accuracy of blood gas analysis by the EPOC device in comparison to a stationary device was adequate for clinical use. Because of its portability and ease of handling, EPOC is a highly valuable diagnostic tool for use in everyday practice as well as and under challenging field conditions. Grants: Siemens Healthcare provided the devices, Lunge Zurich