The Chemistry of the Higher Oxides of Nitrogen as Related to the Manufacture, Storage and Administration of Nitrous Oxide

Austin, A. T.

doi:10.1093/bja/39.5.345

Cited by 63 publications

(17 citation statements)

References 3 publications

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“…However, the reactions producing nitrous acid at these NO concentrations are very slow, as is the reaction with dissolved oxygen [7]. Moreover, we observed complete recovery of the NO signal after leading a wet gas sample through a cold trap.…”

Section: Discussionmentioning

confidence: 72%

Water vapour and carbon dioxide decrease nitric oxide readings

Mark¹,

Kort²,

Meijer³

et al. 1997

Eur Respir J

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Measurement of nitric oxide levels in exhaled air is commonly performed using a chemiluminescence detector. However, water vapour and carbon dioxide affect the chemiluminescence process. The influence of these gases at the concentrations present in exhaled air, has not yet been studied.For this in vitro study, mixtures of 50, 100 and 200 parts per billion (ppb) NO in air were prepared and fed into the NO analyser either directly or bubbled through water. Mixtures with CO 2 were prepared by adding 0-10% CO 2 to the diluent air.We found a significant decrease in NO readings in the water-saturated samples compared to the dry gas (p<0.001), strongly dependent on the partial pressure of water. NO levels in exhaled air (mean 10±2 ppb) showed a decrease of 17±3% when waer vapour was not absorbed. From the experiments with CO 2 we found a decrease in NO reading of 1.04±0.07% per volume CO 2 (%).Presence of water vapour, thus, leads to a systematic underestimation of NO levels. Insertion of a water absorber might, therefore, be advantageous. The influence of CO 2 concentrations in the normal respiratory range is negligible. With high expiratory CO 2 levels as applied in permissive hypercapnia, the effects may be substantial. Eur Respir J 1997; 10: 2120-2123 Measurement of nitric oxide levels in exhaled air is commonly performed by a chemiluminescence detector, in which NO reacts with O 3 to form high energetic NO 2 *. Only a small fraction (typically less than 1%) of the energy carried by the NO 2 * molecules is dissipated by emission of photons. The major part is dissipated by interaction with other molecules in the reaction chamber. The latter process is called third body quenching, and is dependent on sample composition and reaction chamber pressure. The effect of variations in sample composition and reaction chamber pressure follows the well-known Stern-Volmer relation [1, 2]: PNO 2 B (1+Σ aiPi) where F is the emission signal, B is a proportionality constant which is instrument dependent, PNO 2 is the partial pressure of the NO 2 formed (proportional to the NO concentration in the sample gas), Pi is the partial pressure of the i-th component in the sample gas, and ai is the corresponding quenching constant. The relative quenching (R) can then be defined as the ratio of the NO signal in the presence of the quenching gas and the NO signal without that gas. From Equation 1 it follows that the relative quenching for a single gas can be given as [3]: 1 1 + b.P in which the constant b comprises both instrumental properties and the quenching constant of the gas at the partial pressure (P) in question.Thus, gas composition influences the chemiluminescence signal. Water vapour and CO 2 have quenching constants considerably exceeding those of N 2 and O 2 [3], and may therefore decrease the NO signal. This is a well-known phenomenon in the analysis of combustion engine exhaust gases [2][3][4], where NO detector efficiency may decrease to 60% [3]. However, the composition of exhaust gases is quite different from exhale...

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Section: Discussionmentioning

confidence: 72%

Water vapour and carbon dioxide decrease nitric oxide readings

Mark¹,

Kort²,

Meijer³

et al. 1997

Eur Respir J

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“…The inhalation toxicology of inhaled NO and NO2 at high concentration has been difficult to ascertain separately because ofthe oxidation of NO to NO2 in the presence of oxygen, the oxidation rate being dependent on the temperature, the initial concentration ofNO and the FHO2. The oxidation rate of 10 ppm NO in air at 20'C is slow and 7 h is required for 50% oxidation (10). Inhaled NO diffuses through the lung and binds with hemoglobin in erythrocytes; in contrast, NO2 causes pathological changes in airways and alveoli (39,40).…”

Section: Discussionmentioning

confidence: 99%

“…Despite the widely held misconception, NO in low concentrations in air is only slowly oxidized, and so can be studied independently of the effects of its more toxic product, nitrogen dioxide (NO2) (10). NO is produced in the hot reducing atmosphere near the glowing cone of a cigarette and is inhaled in smoke in concentrations of 400-1,000 ppm (11).…”

Section: Introductionmentioning

confidence: 99%

Bronchodilator action of inhaled nitric oxide in guinea pigs.

Dupuy

Shore²,

Drazen³

et al. 1992

J. Clin. Invest.

304

129

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The effects of inhaling nitric oxide (NO) on airway mechanics were studied in anesthetized and mechanically ventilated guinea pigs. In animals without induced bronchoconstriction, breathing 300 ppm NO decreased baseline pulmonary resistance (RL) from 0.138±0.004 (mean±SE) to 0.125±0.002 cmH2O/ml s (P < 0.05). When an intravenous infusion of methacholine (3.5-12 ,ug/kg-min) was used to increase RL from 0.143±0.008 to 0.474±0.041 cmH2O/ml. s (P < 0.05), inhalation of 5-300 ppm NO-containing gas mixtures produced a dose-related, rapid, consistent, and reversible reduction of RL and an increase of dynamic lung compliance. The onset of bronchodilation was rapid, beginning within 30 s after commencing inhalation. An inhaled NO concentration of 15.0±2.1 ppm was required to reduce RL by 50% of the induced bronchoconstriction. Inhalation of 100 ppm NO for 1 h did not produce tolerance to its bronchodilator effect nor did it induce substantial methemoglobinemia (< 2%). The bronchodilating effects of NO were additive with the effects of inhaled terbutaline, irrespective of the sequence of NO and terbutaline administration. Inhaling aerosol generated from S-nitroso-N-acetylpenicillamine also induced a rapid and profound decrease of RL from 0.453±0.022 to 0.287±0.022 cmH2O/ml s, which lasted for over 15 min in guinea pigs bronchoconstricted with methacholine. Our results indicate that low levels ofinhaled gaseous NO, or an aerosolized NO-releasing compound are potent bronchodilators in guinea pigs. (J. Clin. Invest. 1992. 90:421428.)

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“…The chemiluminescence assay is highly specific for NO, and there is no interference from other nitrogen oxides (27). At an NO level of 10,000 ppb in air, containing 20% oxygen, there is an oxidation rate of 25% after 2.3 hours (28,29). The recovery rate for the silicone catheter placed for 5 minutes in a canister with NO at known concentration was 40%.…”

Section: Methodsmentioning

confidence: 99%