Ozone measurement with silica cartidges and HRGC-MS analysis.

Ozone in ambient air is collected onto silica gel cartridges impregnated with pentafluorophenylhydrazine (PFPH) and 1,2-di(4-pyridyl)ethylene (DPE), so that the pyridine-4 aldehyde formed by DPE oxidation is converted into the corresponding PFPH derivative (PPH). The latter product is determined by HRGC/MS. Since the ozonolysis reaction proceeds stoichiometrically on the cartridge, there is no need for calibration in the gas phase with a standardized ozone source. When compared with UV photometry analyzers, this active chromatographic method (ACM) demonstrates a very good accuracy (ACM/UV photometer = 0.97) and precision (12.0-14.0%) under both laboratory and field sampling conditions at ozone concentrations of 20-200 microg m(-3) and exposure times of 1-3 h. The sampling performance was found to be insensitive to relative humidity (r.h.) variations in the 25-90% range and any interference effects could not be observed from various agents, except light, which can be eliminated by using an aluminium shelter. The detection limit for ozone achievable with the ACM in air samples collected at 0.5 L min(-1) for 1 h was found better than 0.5 microg m(-3).

Dynamic system for the calibration of semi-volatile carbonyl compounds in air.

A dynamic calibration system designed for generating accurate and precise concentrations of semi-volatile carbonyls in the ppb (v/v) (ppbv)-ppt (v/v) (pptv) range has been developed and tested. Alkanals from C6 to C9 were used as test compounds. Diffusion rates of their vapours from capillary tubes were determined theoretically and with two methods whose accuracy was independently evaluated with liquid standard solutions. Methods selected for testing the calibration system were those commonly used for the selective quantification of carbonyls in air. One is based on the well-known reaction with 2,4-dinitrophenylhydrazine (DNPH), followed by the analysis of formed hydrazones by HPLC-UV. The other is based on the retention of carbonyls on graphitic carbon adsorbents, followed by MS detection of the sample injected into a capillary column by thermal desorption. A good consistency was found between the values of the diffusion rates determined by the two methods. The scatter between the two methods was in the range of +/-10% when diffusion rates of ca. 1 ng/s were attained. Experimental values closely approached those calculated by applying the equation describing the diffusion of a vapour in equilibrium with the liquid through a capillary tube.

Outcome of intensive care in patients with HIV infection.

OBJECTIVES: To examine ICU admission rates and diagnoses of patients with HIV infection and to determine the outcomes of different critical illnesses. DESIGN: Consecutive enrollment of patients admitted to the ICU with confirmed HIV infection or an AIDS-defining diagnosis. SETTING: Medical ICU of an urban teaching hospital. PATIENTS: 65 adult patients with documented HIV infection or AIDS-defining disorder. INTERVENTIONS: Standard care. RESULTS: In 1 year, there were 1,550 hospital admissions for patients with HIV infection, and 65 (4.2%) were admitted to the ICU. The mortality rate of patients admitted to the ICU was 51%; 35 (54%) were admitted with respiratory failure, 22 of whom had Pneumocystis carinii pneumonia (PCP). Sixteen patients with PCP required mechanical ventilation, and 13 (81%) died despite treatment with adjunctive corticosteroids. Other causes of respiratory failure included bacterial pneumonia, pulmonary tuberculosis, adult respiratory distress syndrome, and pulmonary Kaposi's sarcoma. Overall, 22 of 35 (63%) patients with respiratory failure died in the hospital. Thirty patients (46%) were admitted because of sepsis, neurologic disease, congestive heart failure, hypotension, or drug overdose. These patients had a mortality rate of 37%. Prior antiretroviral and anti-Pneumocystis prophylaxis did not influence outcome, but a body weight of 10% or more below ideal at the time of admission predicted poor survival. CONCLUSION: There is a diverse range of indications for critical care in patients with HIV infection. Although respiratory failure due to PCP was the most common reason for admission to the ICU, it accounted for only 34% of the cases. The prognosis of PCP in patients who require mechanical ventilation despite adjunctive corticosteroid treatment is poor.

Demographic influences on asthma hospital admission rates in New York City.

Surveillance reports describe an increase in asthma prevalence, and cite New York City as an area of excessive asthma mortality. To assess trends and the influence of geography, race, and ethnicity on hospital admission rates for asthma between 1989 and 1991, data of all admissions for asthma to New York City hospitals were reviewed. The average citywide annual hospital admission rate was 681 per 100,000 population, and the racial and ethnic distribution was 1,003 per 100,000 Hispanic patients, 810 per 100,000 for blacks, and 242 per 100,000 for whites (p < 0.0001). Bronx and Manhattan had the highest admissions rates, and contained a few zip codes with very high rates. In these zip codes, admission rates were consistently highest among Hispanics, followed by blacks and whites. New York City asthma admission rates increased 12.7 percent during the study. Very high admission rates among Hispanic patients and high rates in blacks, in specific geographic areas, are responsible for this trend. Targeted education and treatment programs could reduce hospital admissions and mortality in small geographic areas with high asthma morbidity.

Outcome of intensive care for patients with AIDS.

Data on the outcome of intensive care for patients with AIDS have been reported since 1984. Most published statistics focus on the outcome of respiratory failure due to Pneumocystis carinii pneumonia, the most frequent reason for admission to the ICU. Survival appears to be improving in recent years, partly due to the use of adjunctive corticosteroid therapy.

Characterization of a rural area in terms of dry and wet deposition.

Atmospheric gaseous pollutants (NO2, SO2, NH3, HNO3) and related ionic species in water-soluble fine particulates and rainwater were monitored from September 1986 to January 1987 with the aim of estimating the acid deposition over a rural area near Rome. A wet-only rain collector and an annular denuder-filter pack sampling system for gases and aerosols were employed to avoid chemical artifact formation. A comparison of the wet and dry deposition rates indicates that atmospheric removal by precipitation was the dominant sink for sulfate and nitrate at the sampling site. Ion balance analysis showed that the main compounds present in aerosols were (NH4)2SO4 and NH4NO3, since the ammonium neutralization factor approached 100% and the acidity content was very low. The marked enrichment of H+, SO4(2-) and NO3- in precipitation compared with NH4+ could be explained by assuming either that SO2 and NO2 are oxidized in cloud droplets or that acidic sulfate and nitrate are scavenged directly in-cloud or below-cloud.

The determination of tetraalkyl lead in air by a denuder diffusion technique.

A diffusion method for the selective determination of tetraalkyl lead (TAL) in air is proposed. Separation from inorganic lead takes place on an ICl-coated annular denuder, where only TAL is removed during sampling. A differential technique making use of two denuders in series prevents any interference from particulate lead. Analysis of denuder acid extracts by flameless atomic absorption spectrometry provides a direct measure of organic lead thus avoiding a complex solvent extraction procedure.