The Science Journal of the American Association for Respiratory Care

2011 OPEN FORUM Abstracts


Daniel J. Grady1, Terrence F. Smith1, Michael A. Gentile2; 1Respiratory Care, Mission Health System, Asheville, NC; 2Department of Pulmonary and Critical Care Medicine, Duke University Medical Center, Durham, NC

Background: Weaver et. al. have shown that tonometry conducted inside a multiplace hyperbaric chamber produced strong correlations (R2 = 0.98) between predicted and actual dissolved oxygen tensions when the fluid was measured outside the hyperbaric chamber. 1 The purpose of this study was to evaluate the following questions: (1) Can a novel hyperbaric tonometer create supersaturated dissolved oxygen tensions in fluid which are maintained in fluid following removal from hyperbaric conditions? (2) What are the effects of varying tonometry temperature and pressure on supersaturated dissolved oxygen solutions? Method: A novel tonometer was constructed which mixed gas and sterile water under the following 3 groups of conditions (1) equilibration with air at 37 degrees C (n =15), (2) equilibration with 100% oxygen at 37 degrees C (n = 15), and (3) equilibration with 100% oxygen at 17 degrees C (n =15). The pO2 of the supersaturated sterile water solution was immediately analyzed following equilibration, using caution to avoid exposure to ambient air bubbles during removal of the fluid from the tonometer. A Radiometer ABL 330 blood gas analyzer was used for analysis of all tonometered fluid samples. All samples were analyzed under normobaric conditions using an analyzer temperature of 37 degrees C and ambient barometric pressure of 763 mm. Hg. Descriptive statistics and a t-test (alpha =0.05) were calculated for dissolved oxygen tensions for all three experimental groups above. Results: Following equilibration with air at 37 degrees C, the mean pO2 of sterile water was 150 mm. Hg (n = 14, sd = 4.5). Following equilibration with 100% oxygen at 37 degrees C, the mean pO2 was 613 mm. Hg (n=14, sd = 12.4). Surprisingly; when sterile water was equilibrated with 100% oxygen at 17 degrees C and removed from the tonometer to normobaric conditions, the mean pO2 increased to 977 mm. Hg. (n = 14, sd = 11.6). Statistically significant increases in dissolved oxygen tension were found between fluid tonometerd with 100% oxygen at 37 degrees C and at 17 degrees C (p < .05). Conclusions: A novel tonometer, which supersaturates fluid with dissolved oxygen gas, may generate hyperbaric levels of dissolved oxygen tensions when the fluid is removed from hyperbaric conditions and analyzed under normobaric conditions. These findings are consistent with the Weaver study. Additional research is necessary to determine possible clinical applications of this technololgy.
Sponsored Research - None
Weaver L, Howe S, and Berlin S. Normobaric Measurement of O2 Tension of Blood and Saline Tonometered Under Hyperbaric O2 Conditions. Journal of Hyperbaric Medicine, Vol 5, No. 1. 1990.