Testing of the AVL OPTI 1 portable blood gas analyzer during inflight conditions

The "AVL OPTI 1" (AVL Medical Instruments, Saint-Ouen l'Aumone, France), a completely automated portable blood gas analyzer, was chosen because of its accuracy under usual sea-level conditions and because of its new technology which broadens the possibilities for in-flight blood determinations: a) a single use cassette made of plexyglass containing the measurement chamber and the aligned sensors required for pO2, pcO2 and pH determination; b) calibration coefficients memorized in a bar code label fixed on the packing material; c) a quality control of each individual cassette prior to the measurement and at least once a day by two standard reference cassettes simulating high and low levels of pH, pcO2 and pO2; and d) a fully automatic introduction of the blood sample. The complete analytical cycle requires about 3 min with a sample volume of 80 microL of whole blood. After the measurement, the cassette containing blood sample is destroyed. Moreover, this device uses optical electrodes or "optodes" (fluorescence sensors). We tested the accuracy and imprecision of pO2 and pcO2 sensors on fresh blood which was equilibrated with four different gas mixtures at four different altitudes (250, 8000, 10,000 and 13,000 ft), simulated in a decompression chamber. Gas measurement optodes had linear responses and were accurate for all measured pO2 and pco2 values (n = 66), except for at high values of PO2 (>150 mmHg) and pco2 (>65 mmHg). The pressure value given by the AVL OPTI 1 was controlled before the experiment began and during the different depression levels. Barometric pressure results showed: a) concordance of pressure values with those of ground instrumentation; b) stable response; and c) absence of hysteresis. We conclude that the performance of the AVL OPTI 1 is satisfactory during inflight conditions.