2002 OPEN FORUM Abstracts
THE EFFECT OF FLOW MANIPULATION ON FIO2 DELIVERY WITH AN AIR-ENTRAINMENT MASK
Nicole Giudici, Youngstown State University, Youngstown Ohio, Teresa A. Volsko, BS, RRT, FAARC, University Hospital Health System Cleveland, Ohio
Background: Clinicians commonly believe that FIO2 changes on an air-entrainment mask are accomplished similarly to those of a simple mask or nasal cannula, adjusting only the flow on the flow meter. However, with an air-entrainment mask, changes in delivered FIO2 are two-prongedÑadjusting the entrainment port on the mask and setting the manufacturerÕs recommended flow rate. The purpose of this study was to evaluate the effect flow manipulation alone had on FIO2 delivered by an air-entrainment mask. We hypothesized that changes in flow only would not significantly change delivered FIO2.
Methods: A face was simulated using a clay model. A Mini Ox III¨ oxygen analyzer was calibrated and placed on the model where the nose is anatomically located (unoccluded). An air-entrainment mask (Hudson RCL¨) was then applied firmly to the clay, assuring no leaks. The entrainment port was adjusted to deliver the desired FIO2 settings (24, 26, 26, 28, 30, 35, 40, and 50%). The FIO2 was analyzed and recorded after a two-minute stabilization time for the recommended flow. Flow was set at -1, -2, +1, and +2 L/min (relative to the manufacturerÕs recommended flow) for each FIO2 setting. FIO2 was analyzed at each flow variation at each FIO2 setting after a two-minute stabilization time. The experimental conditions were repeated three times. Change in FIO2 was calculated as desired FIO2 measured FIO2. Data were analyzed using two-way repeated measures ANOVA. Significance was established at p ² 0.05.
Results: As flow increased or decreased, there was a concomitant statistically significant change in FIO2 across the range of desired FIO2 settings, p < 0.001. The greatest change in FIO2 (1.5%) is seen with the 30% and 35% settings. Mean values (± SD) for the combination of FIO2 settings across all flow variations are represented as summary data in the graph below;
CONCLUSION: Although statistically relevant, the changes made in flow for each desired FIO2 were within the error specifications of the analyzer (± 2%) and would not be clinically significant. FIO2 cannot be reliably adjusted by changing the flow on an entrainment mask.