The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

PORTABLE OXYGEN CONCENTRATOR (POC) FUNCTION DURING HIGH ALTITUDE SIMULATION TEST (HAST)

Michael Czervinske, Bethene L. Gregg; Dept of Respiratory Care Education, University of Kansas Medical Center, Kansas City, KS

Background: Most HAST use 15% oxygen to simulate an altitude of 8,000 feet and a barometric pressure of approximately 567 torr. Patients with pulmonary problems breathe in a 15% oxygen environment with supplemental oxygen supplied via a nasal cannula to determine if arterial oxyhemoglobin saturation levels can be maintained during flight. Typically the cannula is supplied with 2 LPM of 100% oxygen. Several brands of POCs were recently approved for air travel. A POC delivers >90% oxygen concentration at sea level will not function as specified at altitude. We hypothesized that a POC would not deliver a similar oxygen concentration when 15% oxygen was created by a drop in pressure as compared to 15% oxygen at sea level. Methods: We measured the FIO2 produced from a POC for eleven minutes for each of two test conditions: 1) 15% oxygen at sea level and 2) 15% oxygen from reducing the ambient (box) pressure to approximately 564 torr. For condition 1, a body box was flushed with nitrogen to lower the box FIO2 to 15% and maintained by mixing N2 and compressed air. A leak in the box prevented any increase in pressure. For test condition 2, the pressure inside the body box was reduced by applying vacuum to the box until the FIO2 inside the box dropped to 15%. A leak in the box was adjusted to maintain a pressure of -3.68 to -3.72 psi (569.7 to 567.7 torr) subambient pressure measured by a Timeter RT-200 Gas Analyzer. The highest and lowest FIO2 were recorded each minute at both test conditions. One oxygen analyzer measured the FIO2 from the POC and a second oxygen analyzer measured body box FIO2. Breaths were simulated using a Harvard pump to trigger the pulsed dose delivery from the POC. The exhaust gas was isolated by collection in a Tissot bag to prevent changes in body box FIO2. The POC was triggered at 15 bpm and a VT of 380(+/- 13%)mL. All three POC settings (1,2,3) were tested. Each POC setting is the equivalent of its continuous liter flow. Data were analyzed using a paired samples t-test, SPSS 16.0. Results: Table 1 shows the mean differences in FIO2 at each test condition. Conclusions: There was a significant difference in POC performance when tested with 15% oxygen at sea level as compared to 15% oxygen created by dropping the pressure to 567 torr. HAST testing should use an air/oxygen blender set at 71% to simulate a POC to determine which setting maintains the patient’s oxygen saturation at altitude. Sponsored Research - None

Table 1. Mean Differences In FIO2 Delivered By POC.

*p<0.001

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