The Diamedica Draw-Over Vaporizer: a comparison of a new vaporizer with the Oxford Miniature Vaporizer

The Diamedica Draw-Over Vaporizer (DDV) has been developed as an alternative to the Oxford Miniature Vaporizer (OMV). Both can function as draw-over or plenum vaporizers. The performances of these two vaporizers were compared under conditions simulating intermittent positive pressure ventilation (IPPV) and continuous flow (CF). Series 1 experiments were conducted with the vaporizers in water baths at 20, 25 and 30 °C. Vaporizers were tested at dial settings of 1–4% over a range of minute volumes (1.75–6 l.min⁻¹) and flow rates (3–8 l.min⁻¹). Series 2 experiments compared output of the vaporizers over time at ambient temperatures of 20, 25 and 30 °C. A minute volume of 6 l.min⁻¹ (IPPV) and a gas flow of 8 l.min⁻¹ (CF) were used with a vaporizer setting of 2%. Vapour concentrations were recorded at 5-min intervals. In series 1 IPPV experiments, the DDV vaporizer was more accurate, producing significantly fewer vapour concentrations 0.5% more than or less than setting (p = 0.013). The OMV tended to produce more favourable results under continuous flow (p = 0.42). In series 2 experiments, the accuracy of both vaporizers was similar but consistency of output over time was better for the DDV and consistency of output according to differences in ambient temperature was better for the DDV. The OMV produced more vapour concentrations that were markedly higher than dial setting, particularly at high ambient temperatures. The DDV is a suitable alternative to the OMV with some distinct advantages. These include a larger reservoir, tendency towards greater accuracy during IPPV and improved consistency of output.     

Demographic characteristics and prevalence of serologic markers among donors who use the confidential unit exclusion process: the Retrovirus Epidemiology Donor Study

BACKGROUND: Most blood centers utilize a confidential unit exclusion (CUE) process, intended to reduce the risk of transfusion-associated infectious diseases by allowing high-risk donors confidentially to exclude their blood from use for transfusion. The effectiveness of this method remains controversial. STUDY DESIGN AND METHODS: Confirmatory or supplemental test results for antibodies to human immunodeficiency virus, human T-lymphotropic virus type I, and hepatitis C virus, as well as hepatitis B surface antigen and syphilis and screening test results for antibodies to hepatitis B core (antigen) and alanine aminotransferase levels were obtained for approximately 1.8 million units donated during 1991 and 1992 at five blood centers within the United States. The prevalences of these infectious disease markers in units that the donors confidentially excluded (CUE+) and units that the donors did not exclude (CUE-) were calculated and examined within demographic subgroups. RESULTS: Units that were CUE+ were 8 to 41 times more likely to be seropositive for antibodies to human immunodeficiency virus and hepatitis C virus, hepatitis B surface antigen, and syphilis and three to four times more likely to react for antibody to hepatitis B core (antigen) or to have elevated alanine aminotransferase levels than units that were CUE- (p < 0.001). The positive predictive value of CUE (the percentage of CUE+ units that were confirmed seropositive for any marker) was 3.5 percent, and the sensitivity of CUE (the percentage of confirmed-seropositive units that were CUE+) was 2.3 percent. CONCLUSION: The current CUE process has low sensitivity and apparently low positive predictive value, and in many cases, it appeared that donors misunderstood it. Yet, CUE was not a “random process,” as CUE+ units were more likely to be seropositive for any infectious disease marker than CUE- units. This suggests that efforts to improve the CUE system may be warranted. As risk factors for transfusion-transmitted infection become more difficult to identify by history-based screening, however, such efforts may have limited effect.     

Inactivation of human immunodeficiency virus by gamma radiation and its effect on plasma and coagulation factors

The inactivation of HIV by gamma-radiation was studied in frozen and liquid plasma; a reduction of the virus titer of 5 to 6 logs was achieved at doses of 5 to 10 Mrad at -80 degrees C and 2.5 Mrad at 15 degrees C. The effect of irradiation on the biologic activity of a number of coagulation factors in plasma and in lyophilized concentrates of factor VIII (FVIII) and prothrombin complex was examined. A recovery of 85 percent of the biologic activity of therapeutic components present in frozen plasma and in lyophilized coagulation factor concentrates was reached at radiation doses as low as 1.5 and 0.5 Mrad, respectively. As derived from the first-order radiation inactivation curves, the radiosensitive target size of HIV was estimated to be 1 to 3 MDa; the target size of FVIII was estimated to be 130 to 160 kDa. Gamma radiation must be disregarded as a method for the sterilization of plasma and plasma-derived products, because of the low reduction of virus infectivity at radiation doses that still give acceptable recovery of biologic activity of plasma components.     

State of intervention: community stakeholder discourse on teen childbearing in Iowa

The state of teen childbearing in Iowa (USA) is positioned by community leaders as a discursive battleground for intervention. In 2015 meetings with community stakeholders, participants framed ‘culture’ (which they defined as ethnicity and religion) as a barrier in decreasing the state’s teen pregnancy rate and increasing girls’ economic self-sufficiency. The childbearing teen body was, unsurprisingly, portrayed as a public health problem in need of organizational intervention. But how participants linked ‘culture’ to neoliberal ideals was surprising and specific. Utilizing McRobbie’s concept of the ‘real self’ and Foucault’s explication of governmentality, this study draws out the role of neoliberal self-sufficiency in grooming teens to perform adolescent femininity and self-govern. In doing so, it considers community stakeholders’ meaning-making processes. Findings show the interventionist discourse does more than attempt to prevent early pregnancy: it reinforces acceptable and unacceptable pregnant bodies and compels community leaders and practitioners to govern childbearing teen bodies in precise ways.     

Resolution of infection status of human immunodeficiency virus (HIV)- seroindeterminate donors and high-risk seronegative individuals with polymerase chain reaction and virus culture: absence of persistent silent HIV type 1 infection in a high-prevalence area

To address concerns over the prevalence of silent (antibody-negative) infections among blood donors and high-risk populations, a combination of proviral amplification by polymerase chain reaction (PCR) and viral isolation by co-culture techniques was employed to resolve the human immunodeficiency virus type 1 (HIV-1) infection status of well-characterized groups of suspect blood donors and others identified in the blood bank setting. No silent infections were found in 65 follow-up samples from 26 persistently HIV-1-seroindeterminate blood donors, 16 persistently seronegative heterosexual partners of infected transfusion recipients, and 6 high-risk seronegative homosexual men identified through donor look-back investigations. In contrast, 21 seropositive controls tested positive. These results suggest a low prevalence of persistently silent infections in at-risk populations, even in high HIV prevalence regions. The PCR assay, with a co-detected internal positive control, and appropriate confirmatory algorithms, was found to be a useful direct assay to rule out infection, especially in concert with confirmatory virus isolation.     

The portable Glostavent: a new anaesthetic machine for use in difficult situations

A portable version of the Glostavent anaesthetic machine is described in which recent developments in draw-over technology are incorporated into a traditional draw-over anaesthetic system. The additional features include a more efficient reservoir and an improved vaporiser which have enhanced the performance and versatility. The portable Glostavent weighs less than 10 kg and is transported in a container the size of a small suitcase. It can be used to provide inhalational anaesthesia safely and economically in situations where there are no support facilities. It is ideal for use in battlefield or disaster situations and in isolated hospitals in disadvantaged regions of the world.     

An assessment of the efficiency of the Glostavent® ventilator

In parts of the world where supplies of oxygen and electricity are erratic, ventilating patients' lungs can be problematic. Should the electricity supply fail, gas driven ventilators have an advantage as they can continue functioning. However, many are extravagant in their requirement for the driving gas. The Glostavent^® ventilator was designed to minimise these requirements. We measured the duration of ventilation achieved by the Glostavent ventilator using an E-size oxygen cylinder at a range of minute volumes, and the inspired oxygen concentration achieved by recycling the driving gas. The period of mechanical ventilation from a single E-size cylinder ranged from 11 h 8 min (SD 4 min) with a minute volume of 7 l.min⁻¹ to 18 h 15 min (SD 7 min) with a minute volume of 3 l.min⁻¹. The mean fractional inspired oxygen concentration achieved by recycling the driving gas without further inspired oxygen supplementation was 0.33. We conclude that the Glostavent ventilator performs as efficiently and cost effectively as predicted.     

Improving the efficiency of the drawover anaesthetic breathing system

We investigated modifications to the reservoir tube usually used in drawover anaesthetic breathing systems as a method of improving its efficiency and performance. The resulting oxygen concentration was recorded at different oxygen flow rates whilst an artificial lung was being ventilated over a range of minute volumes. Addition of a reservoir bag and valves significantly increased the measured percentage of oxygen at the common gas outlet when compared to a 300-ml reservoir tube. There was no difference in the percentage of oxygen when comparing a reservoir bag and a 600-ml reservoir tube.