The Measure of Treatment Agreement Between Portable and Laboratory Blood Gas Measurements in Guiding Protocol-Driven Ventilator Management

Background: Portable blood gas analyzer and monitor devices are increasingly being used to direct ventilator therapy. The purpose of this study was to evaluate the "measure of treatment agreement" between portable and laboratory blood gas measurements used in guiding protocol-driven ventilator management. Materials and Methods: Using National Institutes of Health Acute Respiratory Distress Syndrome network ventilator management guidelines to manage patient care, measurements taken from the Nonin 8500 M pulse oximeter (SpO(2)), the Novametrix-610 end-tidal CO(2) (ETCO(2)) detector, and the i-STAT 1 (SaO(2), PO(2), pH, PCO(2)) were compared with the recommended treatment from paired laboratory ABL-725 (SaCO(2), PO(2), pH, PCO(2)) measurements. Results: Four hundred forty-six intubated adult intensive care unit patients were studied prospectively. Except for the ETCO(2) (R(2) = 0.460), correlation coefficients between portable and laboratory measurements were high (R(2) >= 0.755). Testing for equivalence, the Nonin-SpO(2), iSTAT-PO(2), iSTAT-pH, and iSTAT-PCO(2) were deemed "equivalent" surrogates to paired ABL measurements. Testing for the limits of agreement found only the iSTAT-PCO(2) to be an acceptable surrogate measurement. The measure of treatment agreement between the portable and paired laboratory blood gas measurements were Nonin-SPO(2) (68%), iSTAT-SaO(2) (73%), iSTAT-PO(2) (97%), iSTAT-pH (88%), iSTAT-PCO(2) (95%), and Novametrix-ETCO(2) (60%). Only the iSTAT-PO(2) and the iSTAT-PCO(2) achieved the >= 95% treatment agreement threshold to be considered as acceptable surrogates to laboratory measurements. Conclusions: The iSTAT-PO(2) and -PCO(2) were portable device measurements acceptable as surrogates to standard clinical laboratory blood gas measurements in guiding protocol-directed ventilator management. The "measure of treatment agreement," based on standardized decisions and measurement thresholds of a protocol, provides a simple method for assessing clinical validity of surrogate measurements.