Ambient Levels Of Nitric Oxide Research Articles

The impact of ambient NO on online measurements of exhaled and nasal NO: The PIAMA study

The guidelines of the American Thoracic Society (ATS) and the European Respiratory Society (ERS) for standardized measurements of exhaled nitric oxide (NO) state that for online measurements the inhaled air should be free of NO. As it is not always possible to create an NO-free environment, inhalation through an NO-scrubber is used. To describe the relationship between ambient NO and measurements of fractional exhaled NO (FENO) and nasal NO (nNO) investigated according to the ATS-ERS guidelines in a large population of children. The present work makes use of data collected during the 8-yr follow-up of the Dutch PIAMA birth cohort study. FENO and nNO were measured in three hospitals in a total of 1005 children with a NIOX chemiluminescence analyser. In two hospitals, almost half of the measured ambient NO levels exceeded 5 p.p.b. Maximum levels were >100 p.p.b. in all hospitals. Despite its large variation, ambient NO did not have an effect on FENO, but it did have a significant impact on nNO in two of the three centres. The currently recommended technique including inhalation through an NO scrubber effectively deals with variable levels of ambient NO on FENO. In contrast, ambient NO has an effect on measurements of nNO.

Weekday/Weekend Differences in Ambient Air Pollutant Concentrations in Atlanta and the Southeastern United States

The authors quantified changes between mean weekday and weekend ambient concentrations of ozone (O3) precursors (volatile organic compounds [VOC], carbon monoxide [CO], nitric oxide, and oxides of nitrogen [NOx]) in Atlanta and surrounding areas to observe how weekend precursor emission levels influenced ambient O3 levels.The authors analyzed CO, nitric oxide (NO), and NOx measurements from 1998 to 2002 and speciated VOC from 1996 to 2003. They observed a strong weekend effect in the Atlanta region, with median daytime (6:00 a.m. to 3:00 p.m. Eastern Standard Time) decreases of 62%, 57%, and 31%, respectively, in the ambient levels of NO, NOx,and CO from Wednesdays to Sundays, during the ozone season (March to October). They also observed significant decreases in ambient VOC levels between Wednesdays and Sundays, with decreases of 28% for the sum of aromatic compounds and 19% for the sum of Photochemical Assessment Monitoring Stations target compounds. Despite large reductions in O3 precursor levels on weekends, day-of-week differences in O3 mixing ratios in and near Atlanta were much smaller. Averaging overall O3-season days, the 1-hr and 8-hr mean peak daily O3 maxima on Sundays were 4.5% and 2.3% lower, respectively, than their mean levels on Wednesdays (median of 14 site differences), with no sites showing statistically significant Wednesday-to-Sunday differences. When restricted to high-O3 days (highest 3 peak O3 days per day of week per site per year), the 1-hr and 8-hr Sunday O3 mixing ratios were 11% and 10% lower, respectively, than their mean peak levels on Wednesdays (median of 14 site differences), with 6 of 14 sites showing statistically significant Wednesday-to-Sunday differences. The analyses of week-day/weekend differences in O3 precursor concentrations show that different emission reductions than normally take place each weekend will be required to achieve major reductions in ambient ozone levels in the Atlanta area.

Analysis of sources and partitioning of oxidant in the UK—Part 1: the NOX-dependence of annual mean concentrations of nitrogen dioxide and ozone

Abstract A description of the NO X -dependence of annual mean concentrations of nitrogen dioxide ( NO 2 ) is an important component of empirical policy models used to investigate the impacts of NO X emissions control measures. Consideration of nitric oxide (NO), NO 2 and ozone ( O 3 ) as a set of chemically coupled species, rather than NO and NO 2 alone, is used to gain additional insights into the factors controlling ambient levels of NO 2 (and O 3 ), and how they vary with NO X concentration. Monitoring data from 66 urban roadside, urban centre, urban background, suburban, urban industrial and rural sites in the UK are used in this analysis. Annual mean [ NO 2 ] vs. [ NO X ] and [ O 3 ] vs. [ NO X ] relationships are defined by establishing, first, how the concentration of `oxidant' ([OX], defined as [ O 3 ] + [ NO 2 ] ) varies with [ NO X ] and, secondly, how the fractional contributions of NO 2 and O 3 to OX (i.e., [ NO 2 ] / [ OX ] and [ O 3 ] / [ OX ] ) vary with [ NO X ] . This allows site-specific relationships describing the NO X -dependence of annual mean NO 2 and O 3 concentrations to be recommended for 56 non-rural sites. The results are also used to derive representative expressions for different regions of the UK, and these are compared with those currently employed in national empirical modelling activities to calculate future annual mean NO 2 concentrations. Because the present methodology decouples factors which relate to chemical partitioning from those which relate to sources of oxidant, the expressions presented here have the flexibility to enable predictions that take account of modest future changes in regional oxidant (i.e. the background ozone level), or changes in local oxidant inputs (e.g., primary NO 2 emissions) which might arise, for example, from modifications in vehicle emissions control technologies or vehicle fleet composition.

Exposure of Intensive Care Unit Nurses to Nitric Oxide and Nitrogen Dioxide During Therapeutic Use of Inhaled Nitric Oxide in Adults With Acute Respiratory Distress Syndrome

Although low concentrations of inhaled nitric oxide may by therapeutic, both nitric oxide and its oxidation product nitrogen dioxide are potentially toxic. The threshold limits for time-weighted average concentrations of nitric oxide and nitrogen dioxide issued by the American Conference of Governmental Industrial Hygienists are 25 and 3 ppm, respectively. The concentrations of these gases in the breathing space of hospital personnel during administration of nitric oxide to adult patients have not been reported. Air was sampled from the breathing zone of intensive care unit nurses via collar-mounted tubes during the nurses' routine duties attending patients who were receiving inhaled nitric oxide at 5 or 20 ppm. The exhaust ports of the mechanical ventilators were left open to the room. Nitric oxide and nitrogen dioxide were chemically assayed as nitrite from sorbent tubes by using spectrophotometry. Ambient nitric oxide levels were measured at sequential distances from the ventilator by using chemiluminescence. The time-weighted average concentrations of inspired gas for nurses during inhaled nitric oxide treatment were 0.45 ppm or less for nitric oxide and less than 0.29 ppm for nitrogen dioxide. Nitric oxide levels at the ventilator during delivery at 20 ppm were 9.2 ppm, but dropped off markedly beyond 0.6 m (2 ft), to a mean of about 30 ppb. Inhaled nitric oxide therapy at doses up to 20 ppm does not appear to pose a risk of excessive occupational exposure to nitric oxide or nitrogen dioxide to nurses during routine delivery of critical care.

Influence of Environmental Concentrations of NO on the Exhaled NO Test

Measurement of levels of exhaled nitric oxide (NO) has been proposed as a noninvasive method for evaluating the degree of airway inflammation in asthmatic patients. Some concern in the interpretation of results of such measurement may arise from possible interference by high environmental concentrations of NO inhaled by these patients. The aim of this study was to verify whether environmental concentrations of NO in the range from 0 to 150 ppb can influence levels of exhaled NO. We tested two groups of subjects. The first group, consisting of 16 subjects, was tested when environmental levels of NO were from 0 to 3 ppb and from 20 to 60 ppb, and exhaled NO mean ppb (+/- SEM) levels were 9.81 +/- 1.43 and 9.78 +/- 1.47 (p = ns) (mean +/- SEM), respectively. The second group, consisting of 30 subjects, was tested at ambient NO concentrations of 0 to 3 ppm, 80 to 100 ppm, and 120 to 150 ppb, and for 18 of these subjects who underwent testing under all three conditions investigated, the mean levels of exhaled NO were 9.23 +/- 1.51, 7.78 +/- 1.19, and 9.33 +/- 1.55 ppb (p = ns), respectively. The results of this study suggest that significantly different ambient levels of NO have no effect on levels of exhaled NO.

An Investigation into Ambient Levels of Traffic-Related Pollutants in Urban Centres: A Case Study of the Seagate, Dundee, United Kingdom

The findings of a local study, investigating the ambient levels of nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO), total organic hydrocarbons (TOC) and total suspended particulates (TSP), for an urban roadside site within the Seagate area of Dundee, United Kingdom, are presented. A 2 week study was initiated as part of a Local Air Quality Management response to results, published under the National Nitrogen Dioxide Survey, which suggested that ambient levels of NO2could be in breach of the regulatory standards for NO2as prescribed by the Expert Panel on Air Quality Standards (EPAQS) and European Community (E.C.). The results of the study clearly show that the observed levels of NO2are inconsistent with those presented within the National Nitrogen Dioxide Survey, and that the diurnal variation of NO2, observed over the 2 week monitoring period, remained well within the appropriate regulatory standard as set out by EPAQS and the E.C. The recorded levels of CO and TSP were similarly found to lie within the appropriate regulatory air quality standards. Possible traffic management measures for improving air quality in the study area have been proposed based on the findings of the study.

Endothelial Function and Oxidant Stress

Both endothelial cells and vascular smooth muscle cells are capable of producing reactive oxygen species from a variety of enzymatic sources. In disease states such as atherosclerosis and hypertension, vascular production of these reactive oxygen metabolites can increase substantially. Increases in the production of superoxide anion can lead to decreases in ambient levels of nitric oxide via a facile radical/radical reaction that occurs more rapidly than the reaction of superoxide anion with superoxide dismutase. This phenomenon alters endothelial regulation of vasomotion in a variety of disease conditions. Recent evidence suggests that the major source of vascular superoxide ion and hydrogen peroxide is a membrane-bound, reduced nicotinamide-adenine dinucleotide (NADH)-dependent oxidase. The activity of this enzyme system is regulated by angiotensin II and is elevated following prolonged exposure to nitroglycerin. Alterations of vascular oxidant state caused by angiotensin II may contribute substantially to vascular pathology and may also provide a link between hypertension and atherosclerosis.

Contamination of Hospital Compressed Air with Nitric Oxide: Unwitting Replacement Therapy

Inhaled nitric oxide (NO) at levels between 5 and 80 ppm has been used experimentally to treat a variety of conditions. NO also is a common environmental air pollutant in industrial regions. As compressed hospital air is drawn from the local environment, we speculated that it may contain NO contamination, which, if present, would provide unwitting inhaled NO therapy to all subjects respiring this compressed gas. NO levels were measured twice daily from ambient hospital air and compressed gas sources driving positive pressure ventilation from two adjacent hospitals and compared with NO levels reported daily by local Environmental Protection Agency sources. An NO chemiluminescence analyzer (Sievers 270B; Boulder, Colo) sensitive to > or =2 parts per billion was used to measure NO levels in ambient air and compressed gas. NO levels in ambient air and hospital compressed air covaried from day to day, and absolute levels of NO differed between hospitals with the difference never exceeding 1.4 ppm (range, 0 to 1.4 ppm; median, 0.07 ppm). The hospital with the highest usage level of compressed air had the highest levels of NO, which approximated ambient levels of NO. NO levels were lowest on weekends in both hospitals. We also documented inadvertent NO contamination in one hospital occurring over 5 days, which corresponded to welding activity near the intake port for fresh gas. This contamination resulted in system-wide NO levels of 5 to 8 ppm. Hospital compressed air contains highly variable levels of NO that tend to covary with ambient NO levels and to be highest when the rate of usage is high enough to preclude natural degradation of NO in 21% oxygen. Assuming that inhaled NO may alter gas exchange, pulmonary hemodynamics, and outcome from acute lung injury, the role of unwitting variable NO of hospital compressed air needs to be evaluated.