1996 OPEN FORUM Abstracts
AMBIENT AIR SCRUBBER FOR EXHALED NITRIC OXIDE STUDIES.
John Newhart RCP., F. Wayne Johnson RCP., Richard N. Channick MD. UCSD Medical Center, San Diego Ca.
INTRODUCTION:We recently embarked on a study at our institution to analyze endogenous exhaled nitric oxide (ENO). ENO is being studied for a variety of implications including its concentration relative to asthma and other pulmonary illnesses. To eliminate error in our studies due to ambient levels of nitric oxide (NO), a scrubber was fabricated to remove NO from inspired gas. It is worth noting that the ambient NO in the laboratory was 25 parts per billion (ppb). This level of background NO could easily influence ENO studies if not scrubbed. Methods: We fabricated the scrubber from a six inch long four inch I.D. clear plastic tube. We filled four inches of the tube with potassium permanganate pellets (Purafill) and two inches with activated charcoal (walnut charcoal). Ambient air is passed through the tube where Purafill converts the NO into nitrogen dioxide (NO2) and in this reaction most of the NO2 is absorbed. The gas then flows through the charcoal which absorbs the balance of the NO2. To evaluate the effectiveness of the scrubber 100ppb and 400ppb respectively were flowed through the scrubber at 81pm. Gas exiting the scrubber was analyzed with an API 200A nitrogen oxides analyzer (Advanced Pollution Instrumentation, San Diego Ca.). The analyzer's NO range was set on 0 to 500ppb. The analyzer was first calibrated with an API 700 Dynamic Dilution Calibrator for span. Zero calibration was done with a API 701 Zero Air Module. Results: Data collection utilizing a source of 100ppb NO resulted in 0ppb at the outlet of the scrubber. A source of 400ppb resulted in .1ppb. CONCLUSION: NO free air (less than 1ppb) can be easily made with a properly assembled plastic canister containing potassium permanganate and activated charcoal.