British Journal of Anaesthesia, Vol 75, Issue 3 330-333, Copyright © 1995 by The Board of Management and Trustees of the British Journal of Anaesthesia
T. Ishibe, T. Sato, T. Hayashi, N. Kato and T. Hata
Inhaled nitric oxide (NO) is used for the treatment of pulmonary
hypertension as a selective pulmonary vasodilator. However, NO is oxidized
rapidly to the more toxic nitrogen dioxide (NO2). Elimination of NO2 from
inspired gas is essential for safe clinical use NO. We therefore
investigated the efficacy of soda lime in absorbing NO2 from NO2-containing
gases. Commercially available soda limes (Soda sorb and Wako lime-A), were
exposed to the following six gas mixtures containing NO and NO2 in a
hypoxic carrier gas for 20 min: No. 1: NO 40 ppm; No. 2: NO 35 ppm and NO2
5 ppm; No. 3: NO 30 ppm and NO2 10 ppm; No. 4: NO 20 ppm and NO2 20 ppm;
No. 5: NO 10 ppm and NO2 30 ppm; and No. 6: NO2 40 ppm. Both types of soda
lime completely absorbed the NO2 in all samples when it was present (Nos
2-6). NO concentration in these gas mixtures was reduced by an amount equal
to the NO2 absorbed by soda lime. NO was absorbed minimally when NO2 was
not present in the mixture. Nitrite was detected from the Wako lime-A
granules exposed to the test gas by the chemical analysis. These findings
suggest that soda lime completely absorbs NO2 by chemical neutralization,
but NO is absorbed as simultaneously absorbed NO2 only where NO and NO2
coexist. Therefore, we conclude that soda lime is useful for NO2 absorption
during NO inhalation therapy but NO monitoring from a point distal to the
soda lime is required for precise control of inspired NO concentration.
LABORATORY INVESTIGATIONS
Absorption of nitrogen dioxide and nitric oxide by soda lime
Department of Anesthesiology, Tottori University Faculty of Medicine, 36-1 Nishi-machi, Yanago, Tottori 683, Japan; Development Division, Taiyo Sanso Co., Ltd, Osaka, Japan
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