The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

ASSESSMENT OF OXYGEN AND CARBON DIOXIDE LEVELS IN A NEGATIVE PRESSURE INDIVIDUAL ISOLATION SYSTEM, ISO-POD

T. Michael Luethge, RRT; Frank Freihaut, BS RRT. John M. Hauser, CHSP,The Nebraska Medical Center, Omaha, NE.

Background: Our facility has opened a Bio-Containment unit to support Homeland Security and to prepare for highly infectious diseases, e.g. SARS. We evaluated a new product designed to isolate an infectious individual for transport within the hospital or from the field to the hospital. This new product, the Iso-Pod T system, is a portable negative pressure HEPA filtered plastic enclosure. We sought to determine if there could be excessive Oxygen (O2) or Carbon Dioxide (CO2) accumulation inside this device under clinical use.

Methods: The Iso-Pod T was set up and tested in three conditions. O2 and CO2 levels were measured in the Iso-Pod T using a Critcare Poet IQ gas analyzer. First, with an individual breathing room air spontaneously, O2 and CO2 levels were assessed at the nares. In the second and third tests, O2 and CO2 concentrations were measured in four quadrants and at three levels within the Iso-Pod T. In these two tests with the enclosure unoccupied, 15 lpm of O2 and then 2.5 lpm of CO2 was added at the head level. The intent of the study design was to evaluate whether there is sufficient flow through the Iso-Pod T air filtration system to clear CO2 and prevent excess accumulation of O2. The flow of O2 added was considered typical for O2 administration with mask. The CO2 added to the enclosure was at a rate 10 times normal adult CO2 minute production.

Results: For the spontaneous breathing individual test, Inspiratory and Expiratory O2 and CO2 levels remained unchanged. In the O2 test the average measured O2 was 29% (range 25% to 60%). In the CO2 test the average measured CO2 was 2.1% (range 0.8% to 3.5%.

Conclusion: The clearance of CO2 by the Iso-Pod T air filtration system during the spontaneous breathing test was adequate. In the areas tested, when adding O2 or CO2, the concentration of these gases within the Iso-pod was not excessive. As expected, the highest levels of O2 and CO2 were found at the test gas introduction site. CO2 levels were higher in the bottom and middle areas of the Iso-Pod.

Iso-Pod T Spontaneous Breathing Test
  INSPIRATION EXPIRATION
Time Minutes CO2 mmHg O2 % CO2 mmHg O2 %
Baseline 0 21 43 16
5 0 21 44 16
15 2 21 44 16
25 2 21 45 16
30 0 21 42 16

Iso-Pod T CO2 environment test (2.5 lpm CO2) and O2 administration test (15 lpm O2)
  Bottom Middle Top
Quadrant CO2 % O2 % CO2 % O2 % CO2 % O2 %
Head 2.1 27 3.5 60 0.8 25
Torso 2.6 26 2.3 27 1.0 29
Thigh 2.6 27 2.3 26 2.4 26
Foot 2.5 26 2.3 26 1.0 25
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