In-vehicle carbon dioxide concentration in commuting cars in Bangkok, Thailand.

It is known that in-vehicle carbon dioxide (CO2) concentration tends to increase due to occupant exhalation when the HVAC (heating, ventilation, and air conditioning) air is in recirculation mode. Field experiments were conducted to measure CO2 concentration during typical commute in Bangkok, Thailand. The measured concentrations agreed with the concentration predicted using first-order mass balance equation, in both recirculating and outside air modes. The long-term transient decay of the concentration when the vehicle was parked and the HVAC system was turned off was also studied. This decay was found to follow Fickian diffusion process. The paper also provides useful operational details of the automotive HVAC system and fresh air ventilation exchange between cabin interior and exterior. IMPLICATIONS: Drivers in tropical Asian countries typically use HVAC recirculation mode in their automobiles. This behavior leads to excessive buildup of cabin CO2 concentration levels. The paper describes the CO2 buildup in a typical commute in Bangkok, Thailand. Auto manufacturers can potentially take measures to alleviate such high concentration levels. The paper also discusses the diffusion of CO2 through the vehicle envelope, an area that has never been investigated before.

Role of red cell distribution width in screening for Hb E trait in population screening for hemoglobin disorders.

The national screening policy for hemoglobinopathies uses the cutoffs for red cell indices mean corpuscular volume >80 and mean corpuscular hemoglobin >27, a strategy known to miss some individuals with Hb E trait (EBT), the most common abnormal hemoglobin in Sri Lanka. We wanted to determine if red cell distribution width (RDW) cutoff values would help in increasing the sensitivity of screening for Hb E trait. High-performance liquid chromatography was carried out as the gold standard to detect hemoglobinopathies and red blood cell parameters with colter counter. Receiver operating characteristic curve was drawn to determine the cutoff value for EBT against ß-trait (BTT) and other anemias. Of the 504 patients, 246 had BTT, 110 had EBT, and 151 had other types of anemias. Mean (SD) RDW among patients with BTT was 16 (2.8), with EBT 14.5 (2.9), and with other anemias 15.8 (4.2) (P>0.001). With 14.45 as the cutoff for RDW and considering accepted values for mean corpuscular volume >80 and mean corpuscular hemoglobin >27, it gave a predictive sensitivity of 98.2% for EBT. By using RDW cutoff at 14.45 in addition to the accepted screening indices, sensitivity of Hb E trait detection went up to 98.2% from 86.6%. This study highlights the importance of taking RDW into consideration for screening.

Paediatric anaphylaxis: a 5 year retrospective review.

OBJECTIVE: To describe the demographic characteristics, clinical features, causative agents, settings and administered therapy in children presenting with anaphylaxis. METHODS: This was a retrospective case note study of children presenting with anaphylaxis over a 5-year period to the Emergency Department (ED) at the Royal Children's Hospital, Melbourne. RESULTS: One-hundred and twenty-three cases of anaphylaxis in 117 patients were included. There was one death. The median age of presentation was 2.4 years. Home was the most common setting (48%) and food (85%) the most common trigger. Peanut (18%) and cashew nut (13%) were the most common cause of anaphylaxis. The median time from exposure to anaphylaxis for all identifiable agents was 10 min. The median time from onset to therapy was 40 min. Respiratory features were the principal presenting symptoms (97%). Seventeen per cent of subjects had experienced anaphylaxis previously. CONCLUSIONS: This is the largest study of childhood anaphylaxis reported. Major findings are that most children presenting to the ED with anaphylaxis are first-time anaphylactic reactions and the time to administration of therapy is often significantly delayed. Most reactions occurred in the home. Peanut and cashew nut were the most common causes of anaphylaxis in this study population, suggesting that triggers for anaphylaxis in children have not changed significantly over the last decade.

What determines nasal carriage of Staphylococcus aureus?

Nasal carriage of Staphylococcus aureus is an important risk factor for infection by this organism in both community and hospital settings; this article reviews the role of host and bacterial factors in carriage. A host genetic influence appears likely but the phenotypic determinants are unknown. Possibilities include variability in host adhesins, immune response or secretion of antimicrobial molecules. Colonization resistance by S. aureus, together with the observation that persistent carriers often carry a single strain whereas intermittent carriers can be colonized with unrelated strains over time, suggests that bacterial factors could also be involved.

Defining the roles of nucleotide excision repair and recombination in the repair of DNA interstrand cross-links in mammalian cells.

The mechanisms by which DNA interstrand cross-links (ICLs) are repaired in mammalian cells are unclear. Studies in bacteria and yeasts indicate that both nucleotide excision repair (NER) and recombination are required for their removal and that double-strand breaks are produced as repair intermediates in yeast cells. The role of NER and recombination in the repair of ICLs induced by nitrogen mustard (HN2) was investigated using Chinese hamster ovary mutant cell lines. XPF and ERCC1 mutants (defective in genes required for NER and some types of recombination) and XRCC2 and XRCC3 mutants (defective in RAD51-related homologous recombination genes) were highly sensitive to HN2. Cell lines defective in other genes involved in NER (XPB, XPD, and XPG), together with a mutant defective in nonhomologous end joining (XRCC5), showed only mild sensitivity. In agreement with their extreme sensitivity, the XPF and ERCC1 mutants were defective in the incision or "unhooking" step of ICL repair. In contrast, the other mutants defective in NER activities, the XRCC2 and XRCC3 mutants, and the XRCC5 mutant all showed normal unhooking kinetics. Using pulsed-field gel electrophoresis, DNA double-strand breaks (DSBs) were found to be induced following nitrogen mustard treatment. DSB induction and repair were normal in all the NER mutants, including XPF and ERCC1. The XRCC2, XRCC3, and XRCC5 mutants also showed normal induction kinetics. The XRCC2 and XRCC3 homologous recombination mutants were, however, severely impaired in the repair of DSBs. These results define a role for XPF and ERCC1 in the excision of ICLs, but not in the recombinational components of cross-link repair. In addition, homologous recombination but not nonhomologous end joining appears to play an important role in the repair of DSBs resulting from nitrogen mustard treatment.

The role of physical and psychological factors in occupational low back pain: a prospective cohort study.

OBJECTIVE: To examine risk factors for onset of low back pain (LBP) in healthcare workers. METHODS: Nursing students, during their 3 year training period, and 1 year after training were studied in a prospective cohort study, with repeated self reported measurements of determinants of LBP at 6 monthly intervals for 3 years during training, and after a 12 month interval there was an additional final follow up. RESULTS: During training, increased risk of new episodes of LBP was associated with having had LBP at baseline, with part time work, and with a high score on the general health questionnaire (GHQ). A high GHQ score preceded the onset of LBP, in such a way that a high score at the immediately previous follow up increased risk of LBP at the next follow up. 12 Months after training, a history of recurring LBP during training increased the risk of a new episode as did having obtained work as a nurse. A high GHQ score at this follow up was also associated with a concurrently increased risk. Pre-existing GHQ score, either at the end of training or at baseline, had no effect on risk of LBP 12 months after training. CONCLUSIONS: Other than a history of LBP, pre-existing psychological distress was the only factor found to have a pre-existing influence on new episodes of LBP. Increased levels of psychological distress (as measured by the GHQ) preceded the occurrence of new episodes of pain by only short intervening periods, implying a role for acute distress in the onset of the disorder. This finding suggests that management of the onset of occupational LBP may be improved by management of psychological distress.

Role of psychosocial risk factors in work-related low-back pain.

The experience of low-back pain and its psychosocial associates were directly compared among sufferers drawn from three populations, a blue-collar working group, a white-collar working group, and a patient group. Sufferers drawn from the patient population revealed the expected psychological disturbance. There was no evidence of such involvement for sufferers still at work. Disability resulting from low-back pain was positively linearly related to severity of pain for sufferers drawn from working groups, irrespective of psychological disturbance. For patients, on the other hand, the presence of psychological disturbance modified the relationship between severity and disability such that no simple linear relationship existed between the two variables. Work dissatisfaction was not found to be related to the presence of, and did not account for disability resulting from, low-back pain in working subjects.

Is filariasis a trigger for bronchial asthma?

Many Sri Lankan children with cough and wheeze and peripheral blood eosinophilia are treated with diethyl carbamazine (D.E.C.) on the assumption that filaria is the cause. We tried to establish whether filaria can trigger asthma and whether D.E.C. improves bronchial reactivity. In 35 symptomatic and 22 asymptomatic children peripheral blood eosinophil counts, filarial antibody test, stool examination, chest radiography, allergy skin tests and histamine inhalation tests were performed before and after treatment with D.E.C. Most of the symptomatic children were atopic; 1/3 of all children had helminthiasis, positive filarial antibodies and total eosinophil counts of greater than 2,000. Ten children had chest radiographs suggestive of tropical pulmonary eosinophilia. Only in those with intermittent symptoms was there a marked improvement in bronchial reactivity after D.E.C., but baseline peak expiratory flow (P.E.F.) improved in all symptomatic groups. We conclude that 1/3 of the children had filariasis which in an atopic individual may trigger asthma. Both the anti-inflammatory and the anti-filarial action of D.E.C. probably contribute to improvement of bronchial reactivity.