The effect of co-impregnated acids on the performance of Zn-based broad spectrum respirator carbons.

Impregnated activated carbons (IACs) that are used in multi-gas respirator applications usually contain copper and/or zinc impregnants. Co-impregnating with properly selected acids can improve the distribution of the metallic impregnant on the carbon and improve the gas adsorption capacity of the IAC. In this work a comparative study of some common acids co-impregnated with a zinc nitrate (Zn(NO(3))(2)) precursor is performed. The IACs were heated in an inert atmosphere at temperatures which promoted the thermal decomposition of Zn(NO(3))(2) to zinc oxide (ZnO). The gas adsorption properties of the IACs were tested using ammonia (NH(3)), sulphur dioxide (SO(2)) and hydrogen cyanide (HCN) challenge gases. Powder X-ray diffraction (XRD) was used to identify the impregnant species present after heating and to study impregnant distribution. Gravimetric analysis was used to determine the impregnant loading, and help to identify the impregnant species after heating. The interactions between the co-impregnated acid and Zn(NO(3))(2) precursor during heating are discussed. The relationship between impregnant species and gas adsorption capacity is discussed.

The effect of heating temperature and nitric acid treatments on the performance of Cu- and Zn-based broad spectrum respirator carbons.

Impregnated activated carbons (IACs) that are used in broad spectrum gas mask applications have historically contained copper and/or zinc impregnants. The addition of an oxidizing agent, such as nitric acid (HNO(3)) can be useful in distributing the metallic impregnants uniformly on the activated carbon substrate. In this work, we study IACs prepared from copper nitrate (Cu(NO(3))(2)) and zinc nitrate (Zn(NO(3))(2)) precursors as a function of HNO(3) content present in the impregnating solution and as a function of heating temperature. The gas adsorption capacity of the IACs was determined by dynamic flow testing using sulfur dioxide (SO(2)), ammonia (NH(3)), hydrogen cyanide (HCN) and cyclohexane (C(6)H(12)) challenge gases under dry and humid conditions. The thermal decomposition and distribution of the impregnant on the activated carbon substrate is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal analysis techniques. Relationships between gas adsorption capacity, impregnant distribution and the species of surface impregnants are discussed.

A combinatorial approach to screening carbon based materials for respiratory protection.

A combinatorial materials science approach for the discovery of an impregnated activated carbon that can adsorb a wide variety of toxic gases (i.e. a multi-gas carbon) has been developed. This approach presently allows for the parallel preparation and investigation of 64-100 IAC samples at once increasing the rate of discovery of viable multi-gas carbons. Multi-gas carbons were prepared using a solutions handling robot and screened gravimetrically for their effectiveness as gas adsorbents. The method was validated using known gas adsorbent materials such as ZnCl(2), K(2)CO(3) and CuO-impregnated carbons. The calculated adsorption capacities and stoichiometric ratios of reactions for these known gas adsorbent materials, when evaluated using the combinatorial approach, was comparable to the values obtained using traditional methods of analysis. A library of samples prepared by combining various amounts of CuO and ZnO impregnants showed the expected decreasing trend in the calculated stoichiometric ratio of reaction with respect to increasing amount of impregnants added. The method is now ready to use to explore new systems of impregnated activated carbons.

The investigation of copper-based impregnated activated carbons prepared from water-soluble materials for broad spectrum respirator applications.

The preparation of impregnated activated carbons (IACs) from aqueous, copper-containing solutions for broad spectrum gas filtration applications is studied here. Several samples were studied to determine the effect that impregnant loading, impregnant distribution and impregnant recipe had on the overall performance. Dynamic flow testing was used to determine the gas filtration capacity of the IAC samples versus a variety of challenge gases. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) were used to characterize the impregnant distribution on the carbon as a function of impregnant loading. Oven tests were performed to determine the thermal stability of the IAC samples exposed to elevated temperatures. The role impregnant distribution plays in gas filtration capacity and the overall performance of the IAC samples is discussed. The IAC samples prepared in this work were found to have gas filtration capacities as good as or better than broad spectrum respirator carbon samples prepared from the patent literature. IACs impregnated with an aqueous 2.4 M Cu(NO(3))(2)/0.04 M H(3)PO(4).12MoO(3)/4M HNO(3) solution that were heated to 200 degrees C under argon were found to have the best overall performance of the samples studied in this work.

Investigation of copper oxide impregnants prepared from various precursors for respirator carbons.

Copper oxide impregnated activated carbon was prepared by three methods and studied as a respirator carbon. Using techniques such as dynamic flow testing, X-ray diffraction (XRD), thermal analysis, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), copper oxide impregnants, derived from different sources such as basic copper carbonate (Cu(2)CO(3)(OH)(2)), copper nitrate (Cu(NO(3))(2)) and copper chloride (CuCl(2)) reacted with sodium hydroxide (NaOH), have been studied. Dynamic flow tests performed using sulfur dioxide (SO(2)), ammonia (NH(3)) and hydrogen cyanide (HCN) challenge gases allow the determination of the stoichiometric ratio of reaction (SRR) between challenge gas and impregnant. Thermal gravimetric analysis experiments showed that an inert heating environment was required when thermally decomposing the Cu(NO(3))(2) impregnant to CuO to avoid damaging the activated carbon substrate. SEM has been used to investigate dispersal and particle size of the impregnant on the activated carbon. XRD permits the identification of crystalline and amorphous phases as well as the grain size of the impregnant. XRD analysis of samples before and after exposure to SO(2) has allowed the active impregnant in SO(2) adsorption to be identified. The relationship between SRR, impregnant loading and grain size is discussed. Methods to improve impregnant distribution are presented and their impact discussed.

Understanding the role of each ingredient in a basic copper carbonate based impregnation recipe for respirator carbons.

Basic copper carbonate (Cu(2)CO(3)(OH)(2)) is often used as an impregnant in activated carbons for respiratory filters. The mechanisms that allow adsorption of toxic gases by an activated carbon loaded with a Cu(2)CO(3)(OH)(2)-based impregnation recipe are studied here. Several samples were studied to determine the effect of ingredients added during impregnation, impregnant loading and drying temperature on performance. The filtering capacity of the samples is quantified by the stoichiometric ratio of reaction (SRR) between the impregnant and the challenge gas. X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) were used to characterize the impregnant both on and off the carbon as a function of loading and heat-treatment temperature. The influence of the phase and dispersion of the impregnant on the SRR is the focus of this report.

Safety and antibody persistence following Haemophilus influenzae type b conjugate or pneumococcal polysaccharide vaccines given before pregnancy in women of childbearing age and their infants.

BACKGROUND: Immunization of healthy women before pregnancy is a potential approach to providing increased levels of maternal antibody to newborns to protect them from infections occurring during the perinatal period and first months of life. METHODS: Healthy nonpregnant Pima Indian women of childbearing age were randomized to receive one of two Haemophilus influenzae type b (Hib) conjugate vaccines [HbOC or Hib-meningococcal outer membrane protein complex (OMP)] or a 23-valent pneumococcal polysaccharide vaccine (PnPs). Infants received Hib-OMP vaccine at 2, 4 and 12 months of age. Vaccine safety and immunogenicity was evaluated in the women and their infants. RESULTS: Anti-polyribose ribitol phosphate antibody titers were significantly higher in women in both Hib conjugate vaccine groups than in the pneumococcal vaccine group throughout the 37-month observation period. Antibody responses to HbOC vaccine were significantly higher than those to Hib-OMP. A subsequent booster dose of each Hib conjugate vaccine induced reactions and antibody responses similar to those of the first dose. Infants born to mothers immunized with Hib vaccines compared with PnPs had significantly higher polyribose ribitol phosphate-specific IgG antibody titers at birth and 2 months of age but lower antibody responses to Hib-OMP at 6 months and similar titers before and after boosting with Hib-OMP at 1 year of age. By contrast women immunized with PnPs did not have significantly elevated concentrations of pneumococcal-specific antibody at delivery, and their infants had pneumococcal antibody titers similar to those of infants born to mothers who did not receive pneumococcal vaccine before pregnancy. CONCLUSION: Hib conjugate vaccine given to women before pregnancy significantly increased the proportion of infants who had protective Hib antibody levels at birth and 2 months of age.

Prevention of Haemophilus influenzae type b infections in high-risk infants treated with bacterial polysaccharide immune globulin.

Apache Indian infants have a high frequency of Haemophilus influenzae type b (Hib) and pneumococcal infections. Forty percent of Hib infections in these infants occur before the age of six months, when active immunization may not be protective. To evaluate the efficacy of passive immunization with a human hyperimmune globulin (bacterial polysaccharide immune globulin [BPIG]) prepared from the plasma of immunized adult donors, we randomly assigned 703 infants in a double-blind fashion to receive 0.5 ml of BPIG per kilogram of body weight (n = 353) or 0.5 ml of saline (n = 350) intramuscularly at 2, 6, and 10 months of age. Hib-antibody levels were significantly higher in BPIG recipients than in placebo recipients at 4, 6, and 10 months of age (P less than 0.001). During the first 90 days after BPIG or placebo injection, no Hib or pneumococcal infections were detected in the BPIG group, whereas seven Hib infections (six cases of bacteremia and one of meningitis) and four pneumococcal infections (bacteremia) were detected in the placebo group (P = 0.007 and 0.06, respectively). During the fourth month, one case of Hib meningitis and two cases of pneumococcal bacteremia developed in the BPIG group, whereas there were no Hib or pneumococcal infections in the placebo group. We conclude that BPIG given at four-month intervals provided significant protection against serious Hib disease for three months, and that in high-risk infants it might be used alone, perhaps at three-month intervals, or together with active immunization.

Glycine-based oral rehydration solution: reassessment of safety and efficacy.

We evaluated the safety and efficacy of a glycine-based orally administered rehydration solution by comparing it with a standard oral rehydration solution (ORS) without glycine in a randomized double-blind trial in United States infants (age less than 15 months) given treatment for acute gastroenteritis as inpatients or outpatients. The response to therapy (stool volume and duration of illness) was similar in the two groups, except that in four (13%) of 31 hospitalized infants receiving glycine-ORS hypernatremia developed, (one had symptoms) compared with none of 35 receiving ORS (P less than 0.04). Among the 77 outpatients there were no differences between the groups. This study demonstrates that glycine-ORS did not provide any therapeutic advantage over standard ORS, and hypernatremia developed in some patients receiving glycine-ORS. We suggest that caution be used with this type of solution until further safety studies have been done.

Oral rehydration therapy for acute diarrhea in ambulatory children in the United States: a double-blind comparison of four different solutions.

Oral rehydration solutions containing 50 to 90 mmol/L of sodium have recently been recommended for the treatment of diarrhea in both hospitalized and ambulatory children in the United States. Few data are available, however, from ambulatory US children. Therefore, we conducted a randomized double-blind study comparing the use of four different oral rehydration solutions with differing concentrations of sodium, glucose, and base. Ambulatory children less than 2 years of age with acute diarrhea (N = 140) were randomly chosen to receive solutions containing sodium at 90 (solution A), 50 (solution B), and 30 mmol/L (solutions C and D). All oral rehydration solutions contained 20 g/L of glucose except solution D which contained 50 g/L of glucose. Solution A contained bicarbonate as its base source whereas the other three contained citrate. All but three (98%) children were treated uneventfully according to the study protocol, and there were no differences among groups in measurements of clinical outcome. It was concluded that in ambulatory US children, oral rehydration solutions containing 90, 50, or 30 mmol/L of sodium can be used safely for the treatment of mild acute diarrhea and that citrate is as efficacious as bicarbonate in the correction of acidosis.

Outpatient use of oral rehydration solutions in Apache population: effect of instructions on preparation and contamination.

Oral Rehydration Solutions (ORS) containing 90 and 50 mmol/L sodium have recently been recommended for use in ambulatory children in the U.S. These solutions are now marketed in powder form by some commercial companies. However, few data are available in the U.S. on the accuracy with which the solutions are mixed at home or on the bacterial contamination that may occur during mixing. We evaluated the effect of various forms of instructions on the occurrence of bacterial contamination and accuracy of mixing ORS at home by mothers of patients who were dispensed the dry ingredients of an ORS containing 90 mmol/L sodium at the U.S. Public Health Service Hospital, Whiteriver, Arizona. Patients were randomized to one of the four following groups: group I (23 patients) was given written instructions for mixing the solution along with a pre-marked container; group II (22 patients) was given written instructions only; group III (22 patients) was given a premarked container only; and group IV (19 patients) was given neither. All patients were given oral instructions in the preparation of ORS and were asked to refrigerate the reconstituted ORS. We collected samples of ORS at the patient's home 1 day after the clinic visit, to measure their electrolyte content and to identify any bacterial contamination. Mean Na+ concentrations were significantly lower in the ORS prepared by mothers/guardians in groups that were not given a premarked container [82 +/- 13 (II) and 79 +/- 21 (IV) mmol/L vs. 88 +/- 13 (I) and 92 +/- 14 (III) mmol/L; p less than 0.01].(ABSTRACT TRUNCATED AT 250 WORDS)

Cryoextraction of dislocated lenses.

Twenty-two dislocated lenses were removed using cryoextraction. They occurred in a consecutive series of 1,800 planned intracapsulars. Included in the complete series were 16 dislocated lenses in 3 groups: Marfan's syndrome, homocystinuria and congenital types of dislocations. None of these were removed since the patient's vision was adequate in each case. These patients are still under observation. In one case, we used the Hagler-Calhoun double pronged needle. We think this procedure is entirely too traumatic. In 21 cases, the dislocated lenses were removed intracapsularly. In one instance, the lens nucleus had been dislocated in an earlier operation, and there was advanced secondary glaucoma. The lens was removed with cryosurgery, resulting in a useful eye with no pain. Cryoextraction of dislocated lenses is the least traumatic surgical approach and is the method of choice.