The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts


Jonathan B. Waugh1, David L. Vines2, Donna D. Gardner3, Richard B. Wettstein3; 1Clinical and Diagnostic Sciences, University of Alabama at Birmingham, Birmingham, AL; 2Department of Respiratory Care, Rush University, Chicago, IL; 3Department of Respiratory Care, The University of Texas health science Center at San Antonio, San Antonio, TX

Background: Pulse oximetry and capnography are established, non-invasive methods of monitoring oxygenation and ventilation status respectively. A fuzzy-logic algorithm that combines the 4 variables measured by these methods, oxygen saturation (SpO2), heart rate (HR), end-tidal CO2 (EtCO2), and respiratory rate (RR), into a single variable is found in the Integrated Pulmonary Index (IPI)┬« by Oridion Capnography, Inc. (Needham, MA). Our goals were to determine which of the measured variables had the greatest influence on the calculated IPI and if the integrated measure remained stable with changing conditions (gas composition, delivered flow rates, and mouth position). Methods: 20 adult volunteers (75% female, ages 20-36 yrs.) with normal spirometry were measured. EtCO2 and RR were measured by capnography as subjects breathed heliox (20% oxygen/80% helium) via a non-rebreather mask compared to breathing room air at rest. Participants were coached to keep their frequency between 10-20 bpm as needed while watching a video to help maintain a regular breathing pattern. Each level of testing lasted six minutes and a six minute washout period occurred between each testing period. Results: Analyses used a linear mixed model to account for covariance among the repeated measures on the same subjects. The IPI scale ranges from 1-10 with normal being a high value (8-10). Bivariate analyses (tests of slope between the variables of interest and IPI) revealed that under these conditions increases in IPI were associated with increases in EtCO2 and RR (if within normal ranges for the contributing variables┬Śchanges below/above normal ranges produce a decrease in IPI). A multivariable analysis showed increases in EtCO2, RR, and SpO2 were associated with increases in IPI. A standard deviation (SD) increase in EtCO2 was associated with a 28% increase in a SD of IPI. A SD increase in RR was associated with a 20% increase in a SD of IPI. A SD increase in SpO2 was associated with a 10% increase in a SD of IPI. There was no effect from gas mixture, delivered flow rate, or mouth position (see table). Conclusions: The IPI variable was unaffected by the gas compositions, delivered flow rates, and mouth positions used with this adult sample during resting breathing. The most influential measured variables on IPI under these conditions were EtCO2, RR, and SpO2. A single, reliable variable for respiratory status has potential clinical implications for faster assessment and response. Sponsored Research - Funded by Oridion Capnography, Inc.

IPI Statistics for Effects