The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts


Stephanic S. Diehl, RRT, Kent L. Christopher, MD, RRT. Denver, CO.

BACKGROUND: A new demand oxygen delivery system (DODS) has recently been introduced. The demand oxygen controller (DOC2000-Transtracheal Systems, Inc., Englewood, CO) uses a pressure transducer to sense inspiratory effort. A bolus of 18 to 20 ml of O2 is administered per breath over a selectable inspiratory time (TT) of .5 to 1.5 seconds. A toggle switch selects continuous or demand flow. In contrast, the Oxymatic (CHAD Therapeutics, Inc., Chatsworth, CA) DODS delivers a constant volume of 16.5 ml with an adjustable pulse delivery/breath ratio (1:1, 1:2, 1:3, 1:4). The purpose of this study was to evaluate the adequacy of SpO2 utilizing the DOC2000 with both nasal cannula (NC) and transtracheal oxygen (TTO) during rest (R) and exertion (E). Methods: Ten subjects with chronic hypoxemia secondary to COPD(9) or ILD(1) were studied. All subjects had a mature TTO tract, and R flows of 1 to 4 L/min with a mean TTO duration of 22.1 months. Baseline studies included spirometry and room air (RA) SpO2 measurements. TESTING: Individuals were initially placed on continuous flow(CF)NC and titrated to an SpO2 of 92-94% (Ohmeda Biox 3740, Lousville, CO) and SpO2 results were downloaded to a strip chart recorder (B. Braun Melsungen AG, Germany). ABG's wer simultaneously obtained to assess the SpO2 and SaO2 relationship. Each subject was tested on a different DOC2000 unit connected to a single liquid system (Companion T, Puritan Bennett, Indianapolis, IN). The system was filled at least 15 minutes prior to use and t he accuracy of flow rates was documented with the use of a calibrated rotameter (Fisher-Porter, Warminster, PA). The subjects were then ambulated at their normal pace on level ground for 180 feet. E CFNC rates was titrated in an effort to maintain an SaO2 90-92%. Similarly, R and E titrations with DOC2000 (IT of. 5, .9 and 1.5) were done with NC and TTO. In the event that an adequate SpO2 (>=90% at rest and >=88% with E) was not achieved with maximum flow settings (8 L/min) on the DOC2000, protocol was repeated using the Oxymatic at miximum delivery (1 :1). As per manufacturer's recommendations, the Oxymatic was used with compressed gas O2 and22 psi regulator. EXPERIENCE: Both authors have extensive clinical and research experience with O2 dependent patients as well as several pulse devices. Results: Results (X±SD) showed severe hypoxemia (RA SpO2 x 87%±2.2). The group's mean age was 73.2 years and included 4 women and 6 men. The SpO2 correlated within 1-2% of the measured SaO2. Spirometry showed severe impairment of FEV1 (1.10L±.5) and FVC (1.97L±.6). During R conditions, SaO2 was adequate with CFNC (94%±2), CFTTO (97%±2), and DODS IT of .5 (NC 93%±1.5, TTO 95%±1.5), .9(NC 94%±1.1, TTO 96%±1.5), and 1.5 (NC 94%±1.6, TTO 95%±1.6). Of note, R flow settings with DOC2000 did not need to be increased. Throughout E. SaO2 was adequate (>=88%) in 9 of 10 subjects: CFNC (91%±2), CFTTO (95%±2.2), and DODS .5 (NC 91%±2.3, TTO 93%±2.2), .9 (NC 92%±1.8, TTO 93%±1.9), and 1.5 (NC 92%±2.5, TTO 93%±2.8). Flow settings generally needed to be increased. In the 10th subject, SaO2 was adequate with CFTTO but inadequate with CFNC, DOC2000 and Oxymatic. CONCLUSION: During R conditions, SaO2 achieved with DOC2000, with a variety of IT, was equivalent to CF settings with both NC and TTO. Generally (9 of 10 subjects) adequate SpO2 was achieved with the DOC2000 but flow rates were increased 1-2 L/min. One patient without adequate E SpO2 values on CFNC (1 of 10) was not adequately oxygenated with either DOC2000 or Oxymatic. We suggest that R and E SpO2 titration should be performed when considering a DODS.

Reference: OF-96-124

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